BUILDING CODE COUNCIL

[Filed May 5, 2026, 11:10 a.m.]

Preproposal statement of inquiry was filed as WSR 24-11-128.

Title of Rule and Other Identifying Information: Chapter 51-52 WAC, Adoption and amendment of the 2024 International Mechanical Code (IMC) and 2024 International Fuel Gas Code (IFGC).

Hearing Location(s): On June 10, 2026, 10:00 a.m. - 5:00 p.m., at 1500 Jefferson Street S.E., Olympia, WA 98504, Room #2208; and

On June 12, 2026, [10:00 a.m. - 5:00 p.m.,] at 2426 North Discovery Place, Spokane Valley, WA 99216, Room #109.

Date of Intended Adoption: August 28, 2026.

Submit Written Comments to: State Building Code Council (BCC), 1500 Jefferson Street S.E., Olympia, WA 98504, email sbcc@des.wa.gov, beginning May 6, 2026, 12:00 p.m., by June 12, 2026, 11:59 p.m.

Assistance for Persons with Disabilities: Contact BCC staff, email sbcc@des.wa.gov, by June 1, 2026, 11:59 p.m.

Purpose of the Proposal and Its Anticipated Effects, Including Any Changes in Existing Rules: The proposed rule adopts the 2024 editions of the IMC and IFGC, published by the International Code Council, with state amendments to incorporate proposed changes as adopted by BCC. The rules will provide increased clarity and life safety measures for building construction and use in Washington state.

WAC	Section	Changes in 2024	Rationale/Discussion	Proposal Log Number
51-52-0115	IMC 115.4	Changes "code official" to "authority having jurisdiction"	Aligns requirements for establishment of fines in the IMC and IFGC with other building codes that use the model code language of "authority having jurisdiction" in lieu of the currently amended "code official" term used in the IMC and IFGC Washington state amendments.	24-GP1-095
51-52-0202	IMC Definitions	Not adopting new model code definition: Balanced ventilation system	Washington state already includes amendments that define whole house ventilation systems in both the IMC and International Residential Code for residential ventilation requirements.	24-GP1-096
	IMC Definitions	Effective dispersal volume	Add new definitions of 2027 IMC code change proposal M9-24 to align with ASHRAE 15.	24-GP1-104
	IMC Definitions	Effective dispersal volume charge	Add new definitions of 2027 IMC code change proposal M9-24 to align with ASHRAE 15.	24-GP1-104
	IMC Definitions	Machinery room	The proposed change creates better language for a definition to avoid creating what looks like a requirement.	24-GP1-104
51-52-0401	IMC 401.4	Placement and numerical error	This change is to correct the numbering sequence error and also the location error.	24-GP1-105
	IMC 401.4.3	Updating to model code language of "appliance"	Found to be appropriate to retain the previous model code language using the term appliance manufacturer.	24-GP1-098
51-52-0403	IMC 403.2.1	Updating to align the code language	This proposed change will eliminate potential confusion in code interpretation and enforcement.	24-GP1-101
	IMC 403.3.1.3	Add language to correlate to ASHRAE 62.1-2022 for occupied standby ventilation operation	IMC modernizes demand-controlled ventilation compliance, incorporates ASHRAE 62.1 "OS" provisions, and tightens minimum airflow definitions for healthier, more efficient building ventilation.	24-GP1-106
	IMC 403.4.1	2024 IMC update makes clear that regardless of specific energy recovery ventilator (ERV)/heat recovery ventilator (HRV) exemptions in the energy code, whole house supply and exhaust ventilation is required to maintain air quality and code compliance	Clarifies that occupancy types that do not require an ERV/HRV per the Washington state energy code still require whole house ventilation systems that include both supply and exhaust fans.	24-GP1-108
	IMC 403.4.1	These requirements improve indoor air quality, energy efficiency, and technical reliability by demanding direct outdoor exhaust	Field testing bridges the gap between theoretical and installed performance, safeguarding occupant health by confirming effective contaminant removal in everyday operation.	24-GP1-136
	IMC 403.4.4.1	Aligns Washington whole-house ventilation with best practices; simplifies code; may cut minor costs and improve occupant health	This amendment primarily clarifies and aligns distributed whole-house ventilation requirements in Washington state with best practices, making the code simpler to interpret and enforce, with the potential for minor cost reductions and improved occupant health outcomes.	24-GP1-137
	IMC 403.4.6.1	Adds HVI testing exception for exhaust fans	The exception will enable a broader range of system options for residential occupancies to be used.	24-GP1-097
	IMC 403.4.6.1	Adds HVI laboratory language for testing exhaust fans	The exception will enable a broader range of system options for residential occupancies to be used.	24-GP1-136
	IMC 403.4.6.2	Adds HVI testing exception for exhaust fans	The exception will enable a broader range of system options for residential occupancies to be used.	24-GP1-097
	IMC 403.4.6.2	Adds HVI laboratory language for testing supply fans	Help prevent equipment issues with requiring laboratory testing.	24-GP1-136
	IMC 403.4.6.3	Updating language to include description of air and field	Needed to be specific on air and field.	24-GP1-136
	IMC 403.4.6.4	Updating language to include description of air and field	Needed to be specific on air and field.	24-GP1-136
	IMC 403.4.6.6	Updating language to include description of air and field	Needed to be specific on air and field.	24-GP1-136
	IMC 403.4.7.2	Eliminating exceptions that are no longer applicable	Desire for greater accuracy and reliability in ventilation system testing.	24-GP1-136
	IMC 403.4.7.2.1	Clear design and installation controls, improving ventilation reliability and occupant safety	2024 IMC provides multiple compliance paths for local exhaust duct length.	24-GP1-136
	IMC 403.4.7.3	Installers must conduct field verification of airflow unless certified ratings can meet all code requirements directly	Part of 403.4.7.3.1 that allowed installers not to field test has been removed, meaning installations can no longer rely solely on prescriptive duct sizing and manufacturer ratings for airflow verification.	24-GP1-136
	IMC 403.4.7.3.1	Corrects the new language that was introduced in the 2021 Washington state mechanical code to clarify that compliance with either item 1 or item 2 is required	The update clarifies verification options and streamlines compliance, allowing kitchen exhaust systems to be either field tested or manufacturer certified.	24-GP1-107
51-52-0501	IMC 501.3.1.3	Updating to model code language of "appliance"	Found to be appropriate to retain the previous model code language using the term appliance manufacturer.	24-GP1-098
	IMC 501.3.1	Enforceable code language	Add pointers to chapter 11 sections to correlate to ASHRAE 15-2022.	24-GP1-103
	IMC 512.12.2	These measures ensure circuits remain operational during fire events for life safety systems	The purpose of this proposal is to provide additional options for survivability protection of smoke control system circuits that are applied elsewhere in the code for critical circuits.	24-GP1-074
51-52-0600	IMC 601.5	Enforceable language for air condition	This is specifically important for ERV systems that are required for many occupancies.	24-GP1-099
	IMC 607.2.4	Enforceable language for new code language on air duct systems	New model code section as it should apply to newly installed air duct systems and control wiring.	24-GP1-100
51-52-1101	IMC 1101.1	Operation, installation, and safety checks must follow these most current technical standards for the type of refrigerant used	Refrigeration systems (except for ammonia) are required to comply with the IMC, International Fire Code, and ASHRAE 15/15.2.	24-GP1-109
	IMC 1101.1	Updated CO2 requirements	The scope of IIAR CO2 specifically excludes "Listed equipment or systems."	24-GP1-104
	IMC 1101.2	Updating exceptions for table of factory-built equipment and appliances	Exceptions create a legal pathway for lowering the burden of manufacturing equipment.	24-GP1-113
51-52-1102	IMC 1102.5	Clarify IMC requirements to correlate to latest ASHRAE 15-2022 requirements	Updating model code language to new requirements by ASHRAE.	24-GP1-103
51-52-1103	IMC 1103.1	Updated CO2 requirements	The change allows use of newly approved refrigerants from ongoing ASHRAE 34 updates before they appear in the latest IMC edition, ensuring flexibility despite code timing.	24-GP1-104
	IMC 1103.2	Enabling safer, more practical use of low-GWP refrigerants in residential, commercial, and industrial settings	Updates provide targeted exceptions that leverage newer UL safety standards for flammable refrigerants and balance charge limits with environment type.	24-GP1-112
	IMC 1103.2	Enabling safer, more practical use of low-GWP refrigerants in residential, commercial, and industrial settings	Alternate language for exception 9 that limits the charge to 10.8 pounds based on the charge limit in IEC 60335-2-40.	24-GP1-113
51-52-1104	IMC 1104.3.5	Refrigerating systems located in public corridors or lobbies comply with ASHRAE 15 Section 7.5.1.2	This means these systems must meet the safety and refrigerant charge limits specifically outlined in ASHRAE 15 for such spaces, which focus on minimizing risks like refrigerant leaks, fire, and occupant exposure in publicly accessible areas.	24-GP1-104
51-52-1105	IMC 1105.7	Ventilated shafts in buildings, especially with A2L refrigerants	The intent is to prevent energy loss and air leakage from ventilated shafts, which connect to both interior and exterior or conditioned/unconditioned spaces.	24-GP1-104
51-52-1106	IMC 1106.3	Make revisions per 2024 IMC code change Proposal M9-24	Machinery rooms with flammable Class 2 and 3 refrigerants must now be constructed and outfitted per stringent hazardous location standards in NFPA 70 to minimize fire and explosion risk.	24-GP1-104
	IMC 1106.4	Make revisions per 2024 IMC code change Proposal M9-24	Sets clear, tailored requirements for machinery rooms using only mildly flammable A2L and B2L refrigerants, streamlining compliance and safety.	24-GP1-104
51-52-1107	IMC 1107.4	This update helps strength the requirement for piping used in refrigerant systems	The 2024 IMC's update restricting refrigerant pipe materials for residential systems to aluminum, copper, and copper alloy addresses critical health and safety risks associated with refrigerant leaks and piping failures.	24-GP1-109
	IMC 1107.5	Giving requirements for refrigerant systems that follow ASHRAE 15.2 and specifically which fittings may be used	This reinforces health and safety by ensuring fittings are structurally sound and compatible with refrigerants and piping materials, reducing leak risks.	24-GP1-109
51-52-1109	IMC 1109.2.5	Updating to meet with new standards and help protecting piping	This will make the IMC consistent with Section 9.12.1.5 of ASHRAE 15-2022. Note that IMC Section 1109.2.2 still requires piping protection, either within building elements or protective enclosures.	24-GP-110
	IMC 1109.2.5	Added to directly address energy efficiency and air leakage concerns for ventilated shafts	Ventilated refrigerant pipe shafts be built to the same standards as exterior walls.	24-GP1-103
	IMC 1109.2.7	The exception allows a pathway for single dwelling to have refrigerant piping without server cost to meet code compliance	The updated exception allows residential refrigerant piping that is continuous and unobstructed within the shaft to avoid shaft ventilation requirements.	24-GP1-109
	IMC 1109.3.2	Revise to match ASHRAE 15-2022 language	Clarify this applies to natural and mechanical ventilation outlets.	24-GP1-103
51-52-1110	IMC 1110.2	Updating code exceptions for factor manufactured line-sets	Exception simplifies code enforcement by trusting the quality control of factory-manufactured line-sets.	24-GP1-103
51-52-15	IMC 15.2-2022	Safety standard for refrigeration systems in residential applications	Safety standard for refrigeration systems in residential applications.	24-GP1-109
	IMC 15	Updating reference standard name	The reference standard had a change [to] its name that required an update in the model code.	24-GP1-136
51-54-114	IFGC 114.4	Changes "code official" to "authority having jurisdiction"	Aligns requirements for establishment of fines in the IMC and IFGC with other building codes that use the model code language of "authority having jurisdiction" in lieu of the currently amended "code official" term used in the IMC and IFGC Washington state amendments.	24-GP1-095

Reasons Supporting Proposal: RCW 19.27.031 and 19.27.074.

Statutory Authority for Adoption: RCW 19.27.031 and 19.27.074.

Statute Being Implemented: RCW 19.27.031 and 19.27.074.

Rule is not necessitated by federal law, federal or state court decision.

Name of Proponent: BCC, governmental.

Name of Agency Personnel Responsible for Drafting and Implementation: Dustin Curb, 1500 Jefferson Street S.E., Olympia, WA 98504, 360-972-4158; Enforcement: Local jurisdictions having authority.

A school district fiscal impact statement is not required under RCW 28A.305.135.

A cost-benefit analysis is required under RCW 34.05.328. A preliminary cost-benefit analysis may be obtained by contacting Dustin Curb, 1500 Jefferson Street S.E., Olympia, WA 98504, phone 360-972-4158, email dustin.curb@des.wa.gov. The preliminary cost-benefit analysis is posted online at https://sbcc.wa.gov/sites/default/files/2026-05/Economic%20Impact%20Master%20IMC%20%20V6%205.4.2026.pdf.

This rule proposal, or portions of the proposal, is exempt from requirements of the Regulatory Fairness Act because the proposal:

Is exempt under RCW 19.85.025(3) as the rules are adopting or incorporating by reference without material change federal statutes or regulations, Washington state statutes, rules of other Washington state agencies, shoreline master programs other than those programs governing shorelines of statewide significance, or, as referenced by Washington state law, national consensus codes that generally establish industry standards, if the material adopted or incorporated regulates the same subject matter and conduct as the adopting or incorporating rule; and rules only correct typographical errors, make address or name changes, or clarify language of a rule without changing its effect.

Explanation of exemptions: There are significant changes to the model code with economic impact. However, the model code changes are exempt under RCW 19.85.025(3) and 34.05.310 (4)(c), and are not part of this report.

Scope of exemption for rule proposal:

Is partially exempt:

Explanation of partial exemptions: Changes are analyzed at an individual proposal level. All proposals are included in the analysis. Changes that occur in the 2024 version of the model code as compared to the 2021 version are not included and are exempt.

The proposed rule does impose more-than-minor costs on businesses.

Please see the posted preliminary cost-benefit analysis at https://sbcc.wa.gov/sites/default/files/2026-05/Economic%20Impact%20Master%20IMC%20%20V6%205.4.2026.pdf. There are costs imposed by the proposed rule, but the costs do not impact small businesses disproportionately. The rule will not affect the distribution of impacted work. The rules do not affect employment, reporting, or recordkeeping.

A copy of the statement may be obtained by contacting Dustin Curb, 1500 Jefferson Street S.E., Olympia, WA 98504, phone 360-972-4158, email dustin.curb@des.wa.gov.

Chapter 51-52 WAC

STATE BUILDING CODE ADOPTION AND AMENDMENT OF THE ((2021))2024 EDITION OF THE INTERNATIONAL MECHANICAL CODE

AMENDATORY SECTION(Amending WSR 23-23-105, filed 11/15/23, effective 3/16/24)

WAC 51-52-003International Mechanical Code.

The ((2021))2024 edition of the International Mechanical Code published by the International Code Council is hereby adopted by reference with the exceptions noted in this chapter of the Washington Administrative Code (WAC).

AMENDATORY SECTION(Amending WSR 04-01-104, filed 12/17/03, effective 7/1/04)

WAC 51-52-007Exceptions.

The exceptions and amendments to the International Mechanical Code contained in the provisions of chapter 19.27 RCW shall apply in case of conflict with any of the provisions of these rules.

The provisions of this code do not apply to temporary growing structures used solely for the commercial production of horticultural plants including ornamental plants, flowers, vegetables, and fruits. "Temporary growing structure" means a structure that has the sides and roof covered with polyethylene, polyvinyl, or similar flexible synthetic material and is used to provide plants with either frost protection or increased heat retention. A temporary growing structure is not considered a building for purposes of this code.

Codes referenced which are not adopted through RCW 19.27.031 or chapter 19.27A RCW shall not apply unless specifically adopted by the authority having jurisdiction. The 2024 International Fuel Gas Code is included in the adoption of this code and amended in WAC 51-52-21000.

AMENDATORY SECTION(Amending WSR 23-23-105, filed 11/15/23, effective 3/16/24)

WAC 51-52-008Implementation.

The International Mechanical Code adopted by chapter 51-52 WAC shall become effective in all counties and cities of this state on ((March 15, 2024))November 1, 2026.

WAC 51-52-0115Section 115—Failure to comply.

115.4 Failure to comply. Any person who shall continue any work after having been served with a stop work order, except such work as that person is directed to perform to remove a violation or unsafe condition, shall be subject to fines established by the authority having jurisdiction.

AMENDATORY SECTION(Amending WSR 23-02-055, 23-12-106, and 23-20-025, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24)

WAC 51-52-0202Section 202—General definitions.

BALANCED WHOLE HOUSE VENTILATION. Any combination of concurrently operating residential dwelling or sleeping unit mechanical exhaust and mechanical supply whereby the total mechanical exhaust airflow rate is within 10 percent or 5 cfm, whichever is greater, of the total mechanical supply airflow rate.

NOT BALANCED WHOLE HOUSE VENTILATION. A whole house ventilation system serving a dwelling or sleeping unit that is not considered balanced in accordance with the definition in this code for balanced whole house ventilation system. Only other than Group R-2 dwelling and sleeping units are allowed in accordance with Section 403.4.4.1 to have not balanced whole house ventilation systems.

BALANCED VENTILATION SYSTEM. Not adopted.

DISTRIBUTED WHOLE HOUSE VENTILATION. A whole house ventilation system shall be considered distributed when it supplies outdoor air directly (not transfer air) to each dwelling or sleeping unit habitable space, (living room, den, office, interior adjacent room, interior adjoining spaces or bedroom), and exhausts air from all kitchens and bathrooms directly outside.

NOT DISTRIBUTED WHOLE HOUSE VENTILATION. A whole house ventilation system shall be considered not distributed when either the supply system or the exhaust system is not distributed. Supply systems are not distributed when a habitable space is supplied with outdoor air to ventilate an interior adjacent room or an interior adjoining space. Exhaust systems are not distributed when all bathrooms and kitchens are not exhausted by the whole house ventilation system. If either the supply system or the exhaust system is not distributed, then the ventilation quality adjustment system coefficient adjustment is required in accordance with Section C403.4.3.

EFFECTIVE DISPERSAL VOLUME. The volume of a space or connected spaces in which leaked refrigerant will disperse.

EFFECTIVE DISPERSAL VOLUME CHARGE (EDVC). The maximum refrigerant charge permitted for an effective dispersal volume.

ENCLOSED KITCHEN. A kitchen whose permanent openings to interior adjacent spaces do not exceed a total of 60 square feet (6 m2).

INTERIOR ADJACENT ROOM. An enclosed room without exterior windows or openings to the outdoors located within a dwelling or sleeping unit that does not have interior unobstructed openings required for an interior adjoining space.

INTERIOR ADJOINING SPACE. A room or space without openings to the outdoors that is naturally ventilated from another habitable space by unobstructed fixed openings size in accordance with Section 402.3.

LOCAL EXHAUST. An exhaust system that uses one or more fans to exhaust air from a specific room or rooms within a residential dwelling or sleeping unit.

MACHINERY ROOM. A designated space meeting the requirements of Sections 1105 and 1106 that contains one or more refrigerating systems or portions thereof.

PERMANENT CONSTRUCTION. Construction that, if removed, would disturb the structural integrity of the building or the fire-resistance rating of a building assembly.

RELIEF AIR. Exhausted return air from a system that provides ventilation for human usage.

REPLACEMENT AIR. Outdoor air that is used to replace air removed from a building through an exhaust system. Replacement air may be derived from one or more of the following: Makeup air, supply air, transfer air, and infiltration. However, the ultimate source of all replacement air is outdoor air. When replacement air exceeds exhaust, the result is exfiltration.

WHOLE HOUSE VENTILATION SYSTEM. A mechanical ventilation system, including fans, controls, and ducts, which replaces, by direct means, air from the habitable rooms with outdoor air.

VENTILATION ZONE. Any indoor area that requires ventilation and comprises one or more spaces with the same occupancy category (see Table 403.3.1.1), occupant density, zone air distribution effectiveness (see Section 403.3.1.1.1.2), and design zone primary airflow per unit area.

AMENDATORY SECTION(Amending WSR 23-23-105, filed 11/15/23, effective 3/16/24)

WAC 51-52-0401Section 401—General.

401.2 Ventilation required. Every occupied space other than enclosed parking garages and buildings used for repair of automobiles shall be ventilated in accordance with Section 401.2.1, 401.2.2 or 401.2.3. Enclosed parking garages and buildings used for repair of automobiles shall be ventilated by mechanical means in accordance with Sections 403 and 404.

401.2.1 Group R occupancies. Ventilation in Group R occupancies shall be provided in accordance with Section 403.4.

401.2.2 Ambulatory care facilities and Group I-2 occupancies. Ambulatory care facilities and Group I-2 occupancies shall be ventilated by mechanical means in accordance with Section 407.

401.2.3 All other occupancies. Ventilation in all other occupancies shall be provided by natural means in accordance with Section 402 or by mechanical means in accordance with Sections 403.1 to 403.7.

401.3 When required. Group R occupancies shall be vented continuously or intermittently in accordance with Section 403.4. Ventilation in all other occupancies shall be provided during the periods that the room or space is occupied.

401.4 Intake opening location. Air intake openings shall comply with all of the following:

1. Intake openings shall be located not less than 10 feet (3048 mm) from lot lines or buildings on the same lot. Lot lines shall not be defined as a separation from a street or public way.

2. Mechanical and gravity outdoor air intake openings shall be located not less than 10 feet (3048 mm) horizontally from any hazardous or noxious contaminant source, such as vents, streets, alleys, parking lots, and loading docks, except as specified in Item 3 or Section 501.3.1. Outdoor air intake openings shall be permitted to be located less than 10 feet (3048 mm) horizontally from streets, alleys, parking garage entries, parking lots, and loading docks provided that the openings are located not less than 25 feet (7620 mm) vertically above such locations. Where openings front on a street or public way, the distance shall be measured from the closest edge of the street or public way.

EXCEPTIONS:	1. Intake air openings providing less than 500 cfm of outdoor air to Group R occupancies are permitted to be located less than 10 feet (3048 mm) horizontally from parking lots provided that the openings are not less than 15 feet (4572 mm) vertically above the parking lot.
	2. Intake air openings providing less than 500 cfm of outdoor air to Group R occupancies are permitted to be located less than 10 feet (3048 mm) horizontally from parking lots provided that the openings are not less than 15 feet (4572 mm) vertically above the clear height for vehicles in the parking garage.
	3. Enclosed parking garage and repair garage ventilation air intakes are permitted to be located less than 10 feet horizontally from or 25 feet vertically above a street, alley, parking lot, and loading dock.

3. Intake openings shall be located not less than 3 feet (914 mm) below contaminant sources where such sources are located within 10 feet (3048 mm) of the opening. Separation is not required between intake air openings, operable openings, and living space exhaust air openings of an individual dwelling unit or sleeping unit where an approved factory-built intake/exhaust combination termination fitting is used to separate the air streams in accordance with the appliance manufacturer's instructions. For these combined terminations, the exhaust air concentration within the intake airflow shall not exceed 10 percent as established by the manufacturer, in accordance with ASHRAE 62.2 Section 6.8, Exception 4. A minimum of three feet (914 mm) separation shall be maintained between other environmental air exhaust outlets and other dwelling or sleeping unit factory-built intake/exhaust combination termination fittings.

4. Intake openings on structures in flood hazard areas shall be at or above the elevation required by Section 1612 of the International Building Code for utilities and attendant equipment.

((EXCEPTION:

Enclosed parking garage and repair garage ventilation air intakes are permitted to be located less than 10 feet horizontally from or 25 feet vertically above a street, alley, parking lot, and loading dock.))

401.7 Testing and balancing. At the discretion of the building official, flow testing may be required to verify that the mechanical system(s) satisfies the requirements of this chapter. Flow testing may be performed using flow hood measuring at the intake or exhaust points of the system, in-line pitot tube, or pitot-traverse type measurement systems in the duct, short term tracer gas measurements, or other means approved by the code official.

AMENDATORY SECTION(Amending WSR 23-23-105, filed 11/15/23, effective 3/16/24)

WAC 51-52-0403Section 403—Mechanical ventilation.

403.1 Ventilation system. Mechanical ventilation shall be provided by a method of supply air and return or exhaust air. The amount of supply air shall be approximately equal to the amount of return and exhaust air. The system shall not be prohibited from producing negative or positive pressure. The system to convey ventilation air shall be designed and installed in accordance with Chapter 6.

403.2 Outdoor air required. The minimum outdoor airflow rate shall be determined in accordance with Section 403.3.

EXCEPTIONS:	1. Where the registered design professional demonstrates that an engineered ventilation system design will prevent the maximum concentration of contaminants from exceeding that obtainable by the rate of outdoor air ventilation determined in accordance with Section 403.3, the minimum required rate of outdoor air shall be reduced in accordance with such engineered system design.
	2. Alternate systems designed in accordance with ASHRAE Standard 62.1 Section 6.2, Ventilation Rate Procedure, shall be permitted.

403.2.1 Recirculation of air. The air required by Section 403.3 shall not be recirculated. Air in excess of that required by Section 403.3 shall not be prohibited from being recirculated as a component of supply air to building spaces, except that:

1. Ventilation air shall not be recirculated from one dwelling to another or to dissimilar occupancies.

2. Supply air to a swimming pool and associated deck areas shall not be recirculated unless such air is dehumidified to maintain the relative humidity of the area at 60 percent or less. Air from this area shall not be recirculated to other spaces where 10 percent or more of the resulting supply airstream consists of air recirculated from these spaces. The design and installation of dehumidification systems shall comply with ANSI/ACCA 10 Manual SPS.

3. Where mechanical exhaust is required by Note b in Table 403.3.1.1, recirculation of air from such spaces shall be prohibited. All air supplied to such spaces shall be exhausted, including any air in excess of that required by Table 403.3.1.1.

4. Where mechanical exhaust is required by Note g in Table 403.3.1.1, mechanical exhaust is required and recirculation from such spaces is prohibited where more than 10 percent of the resulting supply airstream consists of air recirculated from these spaces. Recirculation of air that is contained completely within such spaces shall not be prohibited.

403.3Outdoor air and local exhaust airflow rates. Group R occupancies shall be provided with outdoor air and local exhaust in accordance with Section 403.4. All other buildings intended to be occupied shall be provided with outdoor air and local exhaust in accordance with Section 403.3.1.

403.3.1.1 Outdoor airflow rate. Ventilation systems shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with this section. In each occupiable space, the ventilation system shall be designed to deliver the required rate of outdoor airflow to the breathing zone. Outdoor air shall be supplied directly to each occupiable space from an air handling unit through a fully ducted path or ducted to within 12 inches of the return air opening of a fan-powered terminal unit used to transfer the outdoor air to the occupiable space. The occupant load utilized for design of the ventilation system shall not be less than the number determined from the estimated maximum occupant load rate indicated in Table 403.3.1.1. Ventilation rates for occupancies not represented in Table 403.3.1.1 shall be those for a listed occupancy classification that is most similar in terms of occupant density, activities and building construction; or shall be determined by an approved engineering analysis. The ventilation system, including transfer fan-powered terminal units, shall be designed to supply the required rate of ventilation air continuously during the period the building is occupied, except as otherwise stated in other provisions of the code.

With the exception of smoking lounges, the ventilation rates in Table 403.3.1.1 are based on the absence of smoking in occupiable spaces. Where smoking is anticipated in a space other than a smoking lounge, the ventilation system serving the space shall be designed to provide ventilation over and above that required by Table 403.3.1.1 in accordance with accepted engineering practice.

EXCEPTION:

Where occupancy density is known and documented in the plans, the outside air rate may be based on the design occupant density. Under no circumstance shall the occupancies used result in outside air less than one-half that resulting from application of Table 403.3.1.1 estimated maximum occupancy rates.

Table 403.3.1.1

REQUIRED OUTDOOR VENTILATION AIR

Occupancy Classification		Occupant Density #/1000 ft2a	People Outdoor Airflow Rate in Breathing Zone Rp cfm/Person	Area Outdoor Airflow Rate in Breathing Zone Ra cfm/ft2a	Exhaust Airflow Rate cfm/ft2a
Correctional facilities
	Booking/waiting	50	7.5	0.06	—
	Cells
	Without plumbing fixtures	25	5	0.12	—
	With plumbing fixturesg	25	5	0.12	1.0
	Day room	30	5	0.06	—
	Dining halls	—	—	—	—
	(see "Food and beverage service")	—	—	—	—
	Guard stations	15	5	0.06	—
Dry cleaners, laundries
	Coin-operated dry cleaner	20	15	—	—
	Coin-operated laundries	20	7.5	0.12	—
	Commercial dry cleaner	30	30	—	—
	Commercial laundry	10	5	0.12	—
	Storage, pick up	30	7.5	0.12	—
Education
	Art classroomg	20	10	0.18	0.7
	Auditoriums	150	5	0.06	—
	Classrooms (ages 5 through 8)	25	10	0.12	—
	Classrooms (age 9 plus)	35	10	0.12	—
	Computer lab	25	10	0.12	—
	Corridors (see "Public spaces")	—	—	—	—
	Day care (through age 4)	25	10	0.18	—
	Lecture classroom	65	7.5	0.06	—
	Lecture hall (fixed seats)	150	7.5	0.06	—
	Locker/dressing roomsg	—	—	—	0.25
	Media center	25	10	0.12	—
	Multiuse assembly	100	7.5	0.06	—
	Music/theater/dance	35	10	0.06	—
	Science laboratoriesg	25	10	0.18	1.0
	Smoking loungesb	70	60	—	—
	Sports locker roomsg	—	—	—	0.5
	Wood/metal shopsg	20	10	0.18	0.5
Food and beverage service
	Bars, cocktail lounges	100	7.5	0.18	—
	Cafeteria, fast food	100	7.5	0.18	—
	Dining rooms	70	7.5	0.18	—
	Kitchens (cooking)b	20	7.5	0.12	0.7
Hotels, motels, resorts, and dormitories
	Bathrooms/toilets—privateg	—	—	—	25/50f
	Bedroom/living room	10	5	0.06	—
	Conference/meeting	50	5	0.06	—
	Dormitory sleeping area	20	5	0.06	—
	Gambling casinos	120	7.5	0.18	—
	Lobbies/prefunction	30	7.5	0.06	—
	Multipurpose assembly	120	50	0.06	—
Offices
	Conference rooms	50	5	0.06	—
	Kitchenettesk	25	5	0.06	0.30
	Office spaces	5	5	0.06	—
	Reception areas	30	5	0.06	—
	Telephone/data entry	60	5	0.06	—
	Main entry lobbies	10	5	0.06	—
Private dwellings, single and multiple
	Garages, common for multiple unitsb	—	—	—	0.75
	Kitchensb				See Table 403.4.7
	Living areasc		See Table 403.4.2	—	—
	Toilet rooms and bathroomsg	—	—		See Table 403.4.7
Public spaces
	Corridors serving other than Group R occupancies	—	—	0.06	—
	Corridors serving Group R dwelling or sleeping units with whole house exhaust system	—	—	0.12	—
	Corridors serving Group R dwelling or sleeping units with other than whole house exhaust system	—	—	0.06	—
	Courtrooms	70	5	0.06	—
	Elevator car	—	—	—	1.0
	Elevator lobbies in parking garage	—	—	1.0	—
	Legislative chambers	50	5	0.06	—
	Libraries	10	5	0.12	—
	Museums (children's)	40	7.5	0.12	—
	Museums/galleries	40	7.5	0.06	—
	Places of religious worship	120	5	0.06	—
	Shower room (per showerhead)g	—	—	—	50/20f
	Smoking loungesb	70	60	—	—
	Toilet rooms—Publicg	—	—	—	50/70e
Retail stores, sales floors, and showroom floors
	Dressing rooms	—	—	—	0.25
	Mall common areas	40	7.5	0.06	—
	Sales	15	7.5	0.12	—
	Shipping and receiving	2	10	0.12	—
	Smoking loungesb	70	60	—	—
	Storage rooms	—	—	0.12	—
	Warehouses (see "Storage")	—	10	0.06	—
Specialty shops
	Automotive motor fuel-dispensing stationsb	—	—	—	1.5
	Barber	25	7.5	0.06	0.5
	Beauty salonsb	25	20	0.12	0.6
	Embalming roomsb	—	—	—	2.0
	Nail salonsb,h	25	20	0.12	0.6
	Pet shops (animal areas)b	10	7.5	0.18	0.9
	Supermarkets	8	7.5	0.06	—
Sports and amusement
	Disco/dance floors	100	20	0.06	—
	Bowling alleys (seating areas)	40	10	0.12	—
	Game arcades	20	7.5	0.18	—
	Ice arenas, without combustion enginesj	—	—	0.30	0.5
	Gym, stadium, arena (play area)j	7	20	0.18	—
	Spectator areas	150	7.5	0.06	—
	Swimming pools (pool and deck area)	—	—	0.48	—
	Health club/aerobics room	40	20	0.06	—
	Health club/weight room	10	20	0.06	—
Storage
	Janitor closets, trash rooms, recycling rooms	—	—	—	1.0
	Repair garages, enclosed parking garageb, d	—	—	—	0.75
	Storage rooms, chemical	—	—	—	1.5
	Warehouses	—	—	0.06	—
Theaters
	Auditoriums (see "Education")	—	—	—	—
	Lobbies	150	5	0.06	—
	Stages, studios	70	10	0.06	—
	Ticket booths	60	5	0.06	—
Transportation
	Platforms	100	7.5	0.06	—
	Transportation waiting	100	7.5	0.06	—
Workrooms
	Bank vaults/safe deposit	5	5	0.06	—
	Darkrooms	—	—	—	1.0
	Copy, printing rooms	4	5	0.06	0.5
	Freezer and refrigerated spaces (<50°F)	0	10	0	0
	Meat processingc	10	15	—	—
	Pharmacy (prep. area)	10	5	0.18	—
	Photo studios	10	5	0.12	—
	Computer (without printing)	4	5	0.06	—

For SI:		1 cubic foot per minute = 0.0004719 m3/s, 1 ton = 908 kg, 1 cubic foot per minutes per square foot = 0.00508 m3/(s•m2), °C = [(°F) -32]/1.8, 1 square foot - 0.0929 m2.
a.		Based upon net occupiable floor area.
b.		Mechanical exhaust required and the recirculation of air from such spaces is prohibited. ((Recirculation of air that is contained completely within such spaces shall not be prohibited (see Section 403.2.1, Item 3).))
c.		Spaces unheated or maintained below 50°F are not covered by these requirements unless the occupancy is continuous.
d.		Ventilation systems in enclosed parking garages shall comply with Section 404.
e.		Rates are per water closet or urinal. The higher rate shall be provided where the exhaust system is designed to operate intermittently. The lower rate shall be permitted only where the exhaust system is designed to operate continuously while occupied.
f.		Rates are per room unless otherwise indicated. The higher rate shall be provided where the exhaust system is designed to operate intermittently. The lower rate shall be permitted only where the exhaust system is designed to operate continuously while occupied.
g.		Mechanical exhaust is required and recirculation from such spaces is prohibited. For occupancies other than science laboratories, where there is a wheel-type energy recovery ventilation (ERV) unit in the exhaust system design, the volume of air leaked from the exhaust airstream into the outdoor airstream within the ERV shall be less than 10 percent of the outdoor air volume. Recirculation of air that is contained completely within such spaces shall not be prohibited (see Section 403.2.1, Items 2 and 4).
h.		For nail salons, each manicure and pedicure station shall be provided with a source capture system capable of exhausting not less than 50 cfm per station. Exhaust inlets shall be located in accordance with Section 502.20. Where one or more required source capture systems operate continuously during occupancy, the exhaust rate from such systems shall be permitted to be applied to the exhaust flow rate required by Table 403.3.1.1 for the nail salon.
i.		Reserved.
j.		When combustion equipment is intended to be used on the playing surface, additional dilution ventilation and/or source control shall be provided.
k.		Kitchenettes require exhaust when they contain a domestic cooking appliance range or oven that is installed in accordance with Table 507.1.2. Kitchenettes that only contain a microwave cooking appliance are not required to have exhaust. A kitchenette may not contain commercial cooking appliances that require Type I or Type II exhaust as these occupancies are required to be exhausted to the kitchen category in Table 403.3.1.1.

403.3.1.1.2.3 Multiple zone recirculating systems. For ventilation systems wherein one or more air handlers supply a mixture of outdoor air and recirculated air to more than one ventilation zone, the outdoor air intake flow (Vot) shall be determined in accordance with Sections 403.3.1.1.2.3.1 through 403.3.1.1.2.3.4.

403.3.1.1.2.3.1 Uncorrected outdoor air intake. The uncorrected outdoor air intake flow (Vot) shall be determined in accordance with Equation 4-5.

Vou = D∑all zones(Rp × Pz) + ∑all zones(Ra × Az)(Equation 4-5)

403.3.1.1.2.3.1.1 Occupant diversity. The occupant diversity ratio (D) shall be determined in accordance with Equation 4-6 to account for variations in population within the ventilation zones served by the system.

D = Ps/∑all zonesPz(Equation 4-6)

where:

Ps = System population: The total population in the area served by the system.

EXCEPTION:

Alternative methods to account for occupant diversity shall be permitted, provided the resulting Vouvalue is no less than that determined using Equation 4-5.

403.3.1.1.2.3.1.2 Design system population. Design system population (Ps) shall equal the largest (peak) number of people expected to occupy all ventilation zones served by the ventilation system during use.

Note: Design system population is always equal to or less than the sum of design zone population for all zones in the area served by the system because all zones may or may not be simultaneously occupied at design population.

403.3.1.1.2.3.2 System ventilation efficiency. The system ventilation efficiency (Ev) shall be determined in accordance with Section 403.3.1.1.2.3.3 for the Simplified Procedure or Appendix A of ASHRAE 62.1 for the Alternative Procedure.

Note: These procedures also establish zone minimum primary airflow rates for VAV systems.

403.3.1.1.2.3.3 Simplified procedure.

403.3.1.1.2.3.3.1 System ventilation efficiency. System ventilation efficiency (Ev) shall be determined in accordance with Equation 4-6a or 4-6b.

Ev = 0.88 × D + 0.22 for D < 0.60 (Equation 4-6a)

Ev = 0.75 for D ≥ 0.60 (Equation 4-6b)

403.3.1.1.2.3.3.2 Zone minimum primary airflow. For each zone, the minimum primary airflow (Vpz-min) shall be determined in accordance with Equation 4-7.

Vpz-min = Voz × 1.5 (Equation 4-7)

403.3.1.1.2.3.4 Outdoor air intake. The design outdoor air intake flow (Vot) shall be determined in accordance with Equation 4-8.

Vot = Vou/Ev(Equation 4-8)

403.3.1.3 System operation. The minimum flow rate of outdoor air that the ventilation system must be capable of supplying during its operation shall be permitted to be based on the rate per person indicated in Table 403.3.1.1 and the actual number of occupants present. Where demand-controlled ventilation is employed to adjust the outdoor airflow rate based on the actual number of occupants present, the minimum quantity of outdoor air shall not fall below that determined from the area outdoor airflow rate column of Table 403.3.1.1 during periods when the building is expected to be occupied. For zones in the occupied standby mode, breathing zone outdoor airflow shall be permitted to be reduced to zero for the occupancy categories indicated "OS" in Table 6-1 of ASHRAE 62.1, provided that airflow is restored to Vbz whenever occupancy is detected.

403.3.2 Group R-2, R-3 and R-4 occupancies. This section is not adopted. See Section 403.4.

403.3.2.1 Outdoor air for dwelling units. This section is not adopted.

403.3.2.2 Outdoor air for other spaces. This section is not adopted.

403.3.2.3 Local exhaust. This section is not adopted.

403.3.2.4 System controls. This section is not adopted.

403.4 Group R whole house mechanical ventilation system. Each dwelling unit or sleeping unit shall be equipped with a whole house mechanical ventilation system that complies with Sections 403.4.1 through 403.4.6. Each dwelling unit or sleeping unit shall be equipped with local exhaust complying with Section 403.4.7. All occupied spaces, including public corridors, other than the Group R dwelling units and/or sleeping units, that support these Group R occupancies shall meet the natural ventilation requirements of Section 402 or the mechanical ventilation requirements of Sections 403.1 through 403.3.

EXCEPTION:

Alternate balanced whole house ventilation systems and local exhaust systems subject to the Washington State Energy Code, Residential Provisions serving Group R dwelling units designed and commissioned in accordance with ASHRAE Standard 62.2 are permitted.

403.4.1 System design. The whole house ventilation system shall consist of one or more supply fans((,))and one or more exhaust fans, or an ERV/HRV with ((integral)) fans providing both supply and exhaust; and the associated ducts and controls. Local exhaust fans shall be permitted to serve as part of the whole house ventilation system when provided with the proper controls in accordance with Section 403.4.5. The systems shall be designed and installed to supply and exhaust the minimum outdoor airflow rates in accordance with Section 403.4.2 as corrected by the balanced and/or distributed whole house ventilation system coefficients in accordance with Section 403.4.3 where applicable.

Table 403.4.2

WHOLE HOUSE MECHANICAL VENTILATION AIRFLOW RATE

(CONTINUOUSLY OPERATING SYSTEMS)

Floor Area (ft2)			Bedroomsa
Floor Area (ft2)	1	2	3	4	˃5
<500	30	30	35	45	50
500 - 1000	30	35	40	50	55
1001 - 1500	30	40	45	55	60
1501 - 2000	35	45	50	60	65
2001 - 2500	40	50	55	65	70
2501 - 3000	45	55	60	70	75
3001 - 3500	50	60	65	75	80
3501 - 4000	55	65	70	80	85
4001 - 4500	60	70	75	85	90
4501 - 5000	65	75	80	90	95
a Minimum airflow (Qr) is set at not less than 30 cfm for each dwelling units.

403.4.2 Whole house mechanical ventilation rates. The sleeping unit whole house mechanical ventilation minimum outdoor airflow rate shall be determined in accordance with the breathing zone ventilation rates minimum outdoor airflow rate shall be determined in accordance with the breathing zone ventilation rates requirements of Section 403.3.1.1.1.2 using Equation 4-2. The dwelling unit whole house mechanical ventilation minimum outdoor airflow rate shall be determined in accordance with Equation 4-10 or Table 403.4.2.

Qr = 0.01*Afloor + 7.5*(Nbr + 1) (Equation 4-10)

where:
Qr	=	Ventilation airflow rate, cubic feet per minute (cfm) but not less than 30 cfm for each dwelling unit.
Afloor	=	Conditioned floor area, square feet (ft2)
Nbr	=	Number of bedrooms, not less than one.

Table 403.4.3

SYSTEM COEFFICIENT (Csystem)

System Type	Distributed	Not Distributed
Balanced	1.0	1.25
Not Balanced	1.25	1.5

403.4.3 Ventilation quality adjustment. The minimum whole house ventilation rate from Section 403.4.2 shall be adjusted by the system coefficient in Table 403.4.3 based on the system type not meeting the definition of a balanced whole house ventilation system and/or not meeting the definition of a distributed whole house ventilation system.

Qv = Qr* Csystem(Equation 4-11)

where:
Qv	=	Quality-adjusted ventilation airflow rate in cubic feet per minute (cfm)
Qr	=	Ventilation airflow rate, cubic feet per minute (cfm) from Equation 4-10 or Table 403.4.2
Csystem	=	System coefficient from Table 403.4.3

403.4.4 Whole house ventilation residential occupancies. Residential dwelling and sleeping unit whole house ventilation systems shall meet the requirements of Sections 403.4.4.1 or 403.4.4.2 depending on the occupancy of the residential unit.

403.4.4.1 Whole house ventilation in Group R-2 occupancies. Residential dwelling and sleeping units in Group R-2 occupancies system shall ((include supply and exhaust fans and be))have a distributed whole-house ventilation system that is also a balanced whole house ventilation system in accordance with Section 403.4.6.3. The system shall include a heat or energy recovery ventilator with a sensible heat recovery effectiveness as prescribed in Section C403.3.6 or when selected as an option of R406 of the Washington State Energy Code. The ((whole house ventilation)) system shall operate continuously at not less than the minimum ventilation rate determined in accordance with Section 403.4((. The whole house supply fan shall provide ducted outdoor ventilation air to each habitable space within the residential unit)), unless configured with intermittent off controls in accordance with Section 403.4.6.5 and to one or more of the following rooms: Living room, dining room, or kitchen.

EXCEPTION((S)):

((1. Interior adjoining spaces that are ventilated from another habitable space are not required to have outdoor air ducted directly to the adjoining space. These systems are considered not distributed whole house ventilation systems and shall use the "not distributed" quality adjustment system coefficient in accordance with Section 403.4.3.

2.))Interior adjacent rooms that are ventilated from another habitable space are not required to have outdoor air ducted directly to the interior adjacent room. ((These systems are considered not distributed whole house ventilation systems and shall use the "not distributed" quality adjustment system coefficient in accordance with Section 403.4.3.)) The interior adjacent room shall be provided with a transfer fan with a minimum airflow rate of 30 cfm or with relief air inlet with a minimum airflow of 20 cfm that is connected to the exhaust/relief air inlet of an ERV/HRV whole house ventilation system. Transfer fans that ventilate interior adjacent rooms shall meet the sone rating in Section 403.4.6 and shall have whole house ventilation controls in accordance with Section 403.4.5.

403.4.4.2 Whole house ventilation for other than Group R-2 occupancies. Residential dwelling and sleeping units in other than Group R-2 occupancies, including I-1 condition 2 occupancies, shall have a distributed whole-house mechanical ventilation system with supply and exhaust fans in accordance with Section 403.4.6.1, 403.4.6.2, 403.4.6.3, or 403.4.6.4. The ((whole house ventilation)) system shall operate continuously at not less than the minimum ventilation rate determined in accordance with Section 403.4.2 unless configured with intermittent off controls in accordance with Section 403.4.6.5. ((The whole house supply fan shall provide ducted outdoor ventilation air to each habitable space within the residential unit.))

EXCEPTION((S)):

403.4.5 Whole house ventilation controls.

1. The whole house ventilation system shall be controlled with manual switches, timers or other means that provide for automatic operation of the ventilation system that are readily accessible by the occupant;

2. Whole house mechanical ventilation system shall be provided with controls that enable manual override off of the system by the occupant during periods of poor outdoor air quality. Controls shall include permanent text or a symbol indicating their function. Recommended control permanent labeling to include text similar to the following: "Leave on unless outdoor air quality is very poor." Manual controls shall be provided with ready access for the occupant.

EXCEPTION:

Central whole house mechanical systems with supply air and/or exhaust that serve more than one dwelling or sleep units are not required to have manual override off controls accessible to the occupant.

3. Whole house ventilation systems shall be configured to operate continuously except where intermittent off controls are provided in accordance with Section 403.4.6.5 and allowed by Section 403.4.4.2.

403.4.6 Whole house ventilation system component requirements. Whole house ventilation supply and exhaust fans specified in this section shall have a minimum efficacy as prescribed in the Washington State Energy Code. The fans shall be rated for sound at a maximum of 1.0 sone at design airflow and static pressure conditions. Design and installation of the system or equipment shall be carried out in accordance with manufacturer's installation instructions.

EXCEPTIONS:	1. Central supply or exhaust fans serving multiple residential units do not need to comply with the maximum fan sone requirements.
	2. Interior joining spaces provided with a 30 cfm transfer fan or a 25 square foot permanent opening do not require supply ventilation air directly to the space. Transfer fans shall meet the sone rating above and have whole house ventilation controls in accordance with Section 403.4.5.

403.4.6.1 Exhaust fans. Exhaust fans required shall be ducted directly to the outside in accordance with Section 501.3. Exhaust air outlets shall be designed to limit the pressure difference to the outside to limiting the outlet free area maximum velocity to 500 feet per minute and equipped with backdraft dampers or motorized dampers in accordance with Washington State Energy Code. Exhaust fans shall be HVI-approved laboratory tested and rated in accordance with HVI 915, HVI 916, and HVI 920. Exhaust fans required in this section may be used to provide local ventilation. Exhaust fans serving spaces other than kitchens that are designed for intermittent exhaust rates in Table 403.4.7 shall be provided with occupancy sensors, humidity sensors, timer controls, or pollutant sensor controls to automatically override the fan to the high speed airflow rate. The exhaust fans shall be field tested and verified, and the testing results shall be submitted and posted in accordance with Section 403.4.6.7.

EXCEPTIONS:	1. Central exhaust fans serving multiple residential units do not need to comply with the HVI laboratory testing requirements.
	2. Inlet free area maximum velocity may exceed 500 feet per minute when a factory-built combined exhaust/intake termination fitting is used.
	3. Ventilation exhaust fans integral to a unitary heat pump appliance do not need to comply with the HVI testing requirements.

403.4.6.2 Supply fans. Supply fans used in meeting the requirements of this section shall supply outdoor air from intake openings in accordance with Sections 401.4 and 401.5. Intake air openings shall be designed to limit the pressure difference to the outside to limiting the inlet free area maximum velocity to 500 feet per minute and when designed for intermittent off operation shall be equipped with motorized dampers in accordance with the Washington State Energy Code. Supply fans shall be HVI-approved laboratory tested and rated in accordance with HVI 915, HVI 916, and HVI 920. Where outdoor air is provided to each habitable dwelling unit or sleeping unit by supply fan systems the outdoor air shall be filtered. The filter shall be provided with access for regular maintenance and replacement. The filter shall have a Minimum Efficiency Rating Value (MERV) of at least 8.

EXCEPTIONS:	1. Central supply fans serving multiple residential units do not need to comply with the HVI laboratory testing requirements.
	2. Ventilation supply fans integral to a unitary heat pump appliance do not need to comply with the HVI testing requirements.

403.4.6.3 Balanced whole house ventilation system. A balanced whole house ventilation system shall include both supply and exhaust fans. The supply and exhaust fans shall have airflow that is within 10 percent of each other. The field tested and balanced total mechanical exhaust airflow rate is within 10 percent or 5 cfm, whichever is greater, of the total mechanical supply airflow rate. The ((flow))airflow rate test results shall be submitted and posted in accordance with Section 403.4.6.7. The exhaust fan shall meet the requirements of Section 403.4.6.1. The supply fan shall meet the requirements of Section 403.4.6.2. For Group R-2 dwelling and sleeping units, the system is required to have balanced whole house ventilation but is not required to have distributed whole house ventilation where the not distributed system coefficient from Table 403.4.3 is utilized to correct the whole house mechanical ventilation rate. The system shall be designed and balanced to meet the pressure equalization requirements of Section 501.4. Local exhaust systems that are not a component of the whole-house mechanical ventilation system are exempt from the balanced airflow calculation.

403.4.6.4 Furnace integrated supply. Systems using space condition heating and/or cooling air handler fans for outdoor air supply air distribution are not permitted.

EXCEPTION:

Air handler fans shall be permitted that have multi-speed or variable speed supply airflow control capability with a low speed operation not greater than 25 percent of the rated supply air flow capacity during ventilation only operation. Outdoor air intake openings must meet the provisions of Sections 401.4 and 401.5 and must include a motorized damper that is activated by the whole house ventilation system controller. Intake air openings shall be designed to limit the pressure difference to the outside to limiting the inlet free area maximum velocity to 500 ft per min. The motorized damper must be controlled to maintain the outdoor airflow intake airflow within 10 percent of the whole house mechanical exhaust airflow rate. The supply air handler shall provide supply air to each habitable space in the residential unit. The whole house ventilation system shall include exhaust fans in accordance with Section 403.4.6.1 to meet the pressure equalization requirements of Section 501.4. The ((flow))airflow rate for the outdoor air intake must be field tested and verified at the minimum ventilation fan speed and the maximum heating or cooling fan speed. The results of the test shall be submitted and posted in accordance with Section 403.4.6.7.

403.4.6.5 Intermittent off operation. Whole house mechanical ventilation systems shall be provided with advanced controls that are configured to operate the system with intermittent off operation and shall operate for a least two hours in each four-hour segment. The whole house ventilation airflow rate determined in accordance with Section 403.4.2 as corrected by Section 403.4.3 shall be multiplied by the factor determined in accordance with Table 403.4.6.5.

Table 403.4.6.5

INTERMITTENT WHOLE HOUSE MECHANICAL VENTILATION RATE FACTORSa,b

Run-time Percentage in Each 4-hour Segment	50%	66%	75%	100%
Factora	2	1.5	1.3	1.0

a	For ventilation system run-time values between those given, the factors are permitted to be determined by interpolation.
b	Extrapolation beyond the table is prohibited.

403.4.6.6 Testing. Whole house mechanical ventilation systems shall be tested, balanced and field verified to provide ((a flow))an airflow rate not less than the minimum required by Sections 403.4.2 and 403.4.3. Testing shall be performed according to the ventilation equipment manufacturer's instructions, or by using a flow hood, flow grid, or other airflow measuring device at the mechanical ventilation fan's inlet terminals, outlet terminals or grilles or in the connected ventilation ducts. Where required by the building official, testing shall be conducted by an approved third party. A written report of the results of the test shall be signed by the party conducting the test and provided to the building official and shall be posted in the residential unit in accordance with Section 403.4.6.7.

403.4.6.7 Certificate. A permanent certificate shall be completed by the mechanical contractor, test and balance contractor or other approved party and posted on a wall in the space where the furnace is located, a utility room, or an approved location inside the building. When located on an electrical panel, the certificate shall not cover or obstruct the visibility of the circuit directory label, service disconnect label, or other required labels. The certificate shall list the flow rate determined from the delivered airflow of the whole house mechanical ventilation system as installed and the type of mechanical whole house ventilation system used to comply with Section 403.4.3.

403.4.7 Local exhaust. Bathrooms, toilet rooms and kitchens shall include a local exhaust system. Such local exhaust systems shall have the capacity to exhaust the minimum airflow rate in accordance with Table 403.4.7 and Table 403.3.1.1, including notes. Fans required by this section shall be provided with controls that enable manual override or automatic occupancy sensor, humidity sensor, timer controls, or pollutant sensor controls. An "on/off" switch shall meet this requirement for manual controls. Manual fan controls shall be provided with ready access in the room served by the fan.

Table 403.4.7

MINIMUM EXHAUST RATES

Area to be exhausted	Exhaust Rate
Area to be exhausted	Intermittent	Continuous
Open kitchens	In accordance with Section 403.4.7.3	Not permitted
Enclosed kitchens	In accordance with Section 403.4.7.3	5 ACH based on kitchen volume
Bathrooms - Toilet rooms	50 cfm	20 cfm

403.4.7.1 Whole house exhaust controls. If the local exhaust fan is included in a whole house ventilation system in accordance with Section 403.4.6, the exhaust fan shall be controlled to operate as specified in Section 403.4.5.

403.4.7.2 Local exhaust fans. Exhaust fans and systems shall meet the following criteria.

1. Exhaust fans shall be HVI-approved laboratory tested and rated in accordance with HVI 915, HVI 916, and HVI 920 or equivalent.

2. ((Fan airflow rating and duct))The system shall be designed and installed in accordance with manufacturers' instructions to deliver at least the exhaust airflow required by Table 403.4.7. The airflows required refer to the delivered airflow of the system as installed ((and tested using a flow hood, flow grid, or other airflow measurement device. Local exhaust systems shall be tested and verified to provide a flow rate not less than the minimum required by this section))field verified in accordance with Section 403.4.7.2.1.

3. ((Design and installation of the system or equipment shall be carried out in accordance with manufacturers' installation instructions.

4.)) Intermittent local exhaust ((system))fans serving kitchens shall be rated for sound at a maximum of 3 sones at one or more airflow settings not less than 100 cfm at a static pressure not less than that determined at working speed as specified in HVI 916 Section 7.2.

((5.))4. Continuous local exhaust ((system))fans serving kitchens shall be rated for sound at a maximum of 1 sone at one or more airflow settings not less than 100 cfm at a static pressure not less than that determined at working speed as specified in HVI 916 Section 7.2.

EXCEPTION((S)):	1. ((The installed airflow is not required to be field-verified where an exhaust airflow rating at a pressure of 0.25 in. w.g. may be used, provided the duct sizing meets the prescriptive requirements of Table 403.4.7.2.
	2.)) Remote mounted fans need not meet sound requirements. To be considered for this exception, a remote mounted fan shall be mounted outside the kitchen, and there shall be at least 4 feet (1 m) of ductwork between the fan and the intake grille.

403.4.7.2.1 Duct length. The length of local exhaust ducts shall comply with not less than one of the following:

1. Duct length shall not be limited where the airflow rate of the installed ventilating equipment is field verified by the installer or approved third party to be not less than that required by Table 403.4.7. Field verification shall be performed using an integrated diagnostic tool, flow hood, flow grid, or other airflow measuring device.

2. Duct length shall not exceed 25 feet, provided that the following conditions are met:

2.1.1. There are no more than three elbows.

2.1.2. The rated airflow used to comply with Table 403.4.7 is determined at not less than 0.25 in. w.c.

2.1.3. The equivalent diameter of the duct is not less than that determined using Table 403.4.7.2 at the rated airflow used to comply with Table 403.4.7.

2.1.4. Where flex duct is used, it shall be fully extended and any flex duct bends shall have a bend radius to duct diameter ratio of not less than 1.0.

3. Where a kitchen range hood's rated nominal installed airflow, determined in accordance with HVI 920, is used to comply with Table 403.4.7.3, a duct length of 10 feet shall be permitted, provided that there are not more than two elbows and that the equivalent diameter of the duct is not less than the equivalent diameter of the rating.

Table 403.4.7.2

PRESCRIPTIVE EXHAUST DUCT SIZING

((Fan Tested cfm at 0.25 inches w.g.	Minimum Flex Diameter	Maximum Length in Feet	Minimum Smooth Diameter	Maximum Length in Feet	Maximum Elbowsa
50	4 inches	25	4 inches	70	3
50	5 inches	90	5 inches	100	3
50	6 inches	No Limit	6 inches	No Limit	3
80	4 inchesb	NA	4 inches	20	3
80	5 inches	15	5 inches	100	3
80	6 inches	90	6 inches	No Limit	3
100	5 inchesb	NA	5 inches	50	3
100	6 inches	45	6 inches	No Limit	3
125	6 inches	15	6 inches	No Limit	3
125	7 inches	70	7 inches	No Limit	3

a.		For each additional elbow, subtract 10 feet from length.
b.		Flex ducts of this diameter are not permitted with fans of this size.))

Fan Airflow Rating, CFM, at static pressure ≥ 0.25 in. w.c.	≤50	≤80	≤100	≤125	≤150	≤175	≤200	≤250	≤350	≤400	≤450	≤700	≤800
Duct Type	Minimum Equivalent Diameter, in.a,b,e,f,g
Rigid duct	4d	5	5	6	6	7	7	8	9	10	10	12	12c
Flex duct	4	5	6	6	7	7	8	8	9	10	NP	NP	NP

a.	For circular ducts, the equivalent diameter, De, is equal to the duct diameter. For rectangular ducts with cross-sectional dimensions a and b,
b.	NP = Application of the prescriptive table is not permitted for this scenario.
c.	For this scenario, use of elbows is not permitted.
d.	For this scenario, 4 in. oval duct shall be permitted, provided the minor axis of the oval is not less than 3 in. (75 mm).
e.	3.25" × 10" rectangular duct shall be permitted as a substitute for circular duct diameters up to 6".
f.	3.25" × 14" rectangular duct shall be permitted as a substitute for circular duct diameters up to 7".
g.	4.5" × 18" rectangular duct shall be permitted as a substitute for circular duct diameters up to 10".

403.4.7.3 Local intermittent kitchen exhaust system.Local intermittent kitchen range hoods for domestic cooking appliances shall meet or exceed either the minimum airflow or the minimum capture efficiency in accordance with Table 403.4.7.3. Capture efficiency ratings shall be determined in accordance with ASTM E3087.

EXCEPTION:

Other intermittent kitchen exhaust fans, including downdraft, shall meet or exceed 300 cfm airflow.

Table 403.4.7.3

Kitchen Range Hood Airflow Rates (CFM) and ASTM E3087 Capture Efficiency (CE) Ratings According to Kitchen Range Fuel Type

Hood Over Electric Range	Hood Over Combustion Range
65 percent CE or 160 cfm	80 percent CE or 250 cfm

403.4.7.3.1 Field verification and diagnostic testing for local intermittent kitchen exhaust system. The local exhaust system for kitchens shall be installed to comply with local mechanical exhaust requirements specified in ((Section 403.4.7.3 and))Table 403.4.7.3. The local exhaust systems for kitchens shall either be field tested and verified in accordance with the following procedures ((below to confirm the model is rated by HVI or AHAM to comply with the following requirements)):

1. ((Local intermittent exhaust system for kitchens shall be tested and verified to provide a minimum airflow rate or capture efficiency required by Section 403.4.7.3. Testing shall include verification of the maximum sound rating as specified in Section 403.4.7.2.))Where an airflow rate is used to comply with Section 403.4.7.3, and the airflow rate is field verified in accordance with Item 1 of Section 403.4.7.2.1, the field test shall also comply with the following requirements.

1.1. Testing ((for the intermittent kitchen exhaust systems)) shall occur with the whole house ventilation system operating and with all dwelling unit or sleeping unit entry doors closed. Testing for exhaust systems that require mechanical makeup air in accordance with Section 505.4 shall include verifying that the mechanical makeup air opening is open.

1.2. Testing for a kitchen exhaust system((s)) that requires mechanical makeup air in accordance with Section 505.4 shall include verifying that the mechanical makeup air system is controlled to automatically start.

1.3. Testing for a kitchen exhaust system((s)) that ((do))does not require mechanical makeup air in accordance with Section 505.4 and that ((are))is exempt from pressurize equalization per Section 501.4 shall be ((tested))conducted with operable openings manually opened unless design exhaust airflow can be achieved with all operable openings closed.

1.4. Where required by the building official, testing shall be conducted by an approved third party. A written report of the results of the test shall be signed by the party conducting the test and provided to the building official.

((EXCEPTION:

The installed airflow is not required to be field-verified where an exhaust airflow rating at a pressure of 0.25 in. w.g. is used, provided the duct sizing meets the prescriptive requirements of Table 403.4.7.2.))

2. ((The))Field verification shall utilize certified rating data from HVI Publication 911, AHAM-Certified Range Hood Directory, or another directory of certified product performance ratings approved by the code official for determining compliance. The field verification procedure shall consist of visual inspection of the local intermittent kitchen exhaust system to verify and record the following information:

2.1. The manufacturer name and model number.

2.2. The model is listed in the HVI, AHAM, or equivalent directory.

2.3. The rated airflow value or capture efficiency value, as applicable, listed in the HVI, AHAM, or equivalent directory.

2.4. The sound rating value listed in the HVI, AHAM, or equivalent directory.

2.5. If the value for the rated airflow or capture efficiency given in the directory is greater than or equal to the ((airflow)) requirements specified in Section ((403.4.7.3))403.4.7, and if the value for the sone rating given in the directory is less than or equal to the sone rating requirements specified in Section 403.4.7.2, then the local intermittent kitchen exhaust system complies, otherwise the local intermittent kitchen exhaust system does not comply.

AMENDATORY SECTION(Amending WSR 23-23-105, filed 11/15/23, effective 3/16/24)

WAC 51-52-0501Section 501—General.

501.3.1 Location of exhaust outlets. The termination point of exhaust outlets and ducts discharging to the outdoors shall be located with the following minimum distances:

1. For ducts conveying explosive or flammable vapors, fumes or dusts: 30 feet (9144 mm) from the property line; 10 feet (3048 mm) from operable openings into the building; 6 feet (1829 mm) from exterior walls and roofs; 30 feet (9144 mm) from combustible walls and operable openings into the building which are in the direction of the exhaust discharge; 10 feet (3048 mm) above adjoining grade.

2. For other product-conveying outlets: 10 feet (3048 mm) from property lines; 3 feet (914 mm) from exterior walls and roofs; 10 feet (3048 mm) from operable openings into the building; 10 feet (3048 mm) above adjoining grade.

3. For environmental air exhaust other than enclosed parking garage and transformer vault exhaust: 3 feet (914 mm) from property lines, 3 feet (914 mm) from operable openings into buildings for all occupancies other that Group U, and 10 feet (3048 mm) from mechanical air intakes. Such exhaust shall not be considered hazardous or noxious. Separation is not required between intake air openings and living space exhaust air openings of an individual dwelling unit or sleeping unit where an approved factory-built intake/exhaust combination termination fitting is used to separate the air streams in accordance with the appliance manufacturer's instructions.

EXCEPTIONS:	1. The separation between an air intake and exhaust outlet on a single listed package HVAC unit.
	2. Exhaust from environmental air systems other than garages may be discharged into an open parking garage.
	3. Except for Group I occupancies, where ventilation system design circumstances require building HVAC air to be relieved, such as during economizer operation, such air may be relieved into an open or enclosed parking garage within the same building.

4. Exhaust outlets serving structures in flood hazard areas shall be installed at or above the elevation required by Section 1612 of the International Building Code for utilities and attendant equipment.

5. For enclosed parking garage exhaust system outlets and transformer vault exhaust system outlets: 10 feet (3048 mm) from property lines which separate one lot from another; 10 feet (3048 mm) from operable openings into buildings; 3 feet (914 mm) horizontally from, 10 feet above, or 10 feet below adjoining finished walkways.

6. For transformer vault exhaust system outlets, subject to the requirements of NFPA 70 Section 450.45: Ten feet (3048 mm) from fire escapes, required means of egress at the exterior of the building, elements of exit discharge, exterior combustible materials, and openings that are not protected in accordance with Section 705.8 of the International Building Code; 10 feet (3048 mm) from property lines which separate one lot from another; 10 feet (3048 mm) from operable openings into buildings; 10 feet (3048 mm) above walkways.

7. For elevator machinery rooms in enclosed or open parking garages: Exhaust outlets may discharge air directly into the parking garage.

8. For specific systems see the following sections:

8.1. Clothes dryer exhaust, Section 504.4.

8.2. Kitchen hoods and other kitchen exhaust equipment, Sections 506.3.13, 506.4 and 506.5.

8.3. Dust stock and refuse conveying systems, Section 511.2.

8.4. Subslab soil exhaust systems, Section 512.4.

8.5. Smoke control systems, Section 513.10.3.

8.6. Refrigerant discharge for relief devices, Section 1105.7.

8.7. Machinery room discharge, Section 1105.6.1.

8.8. Natural ventilation and mechanical exhaust discharge for A2L and B2L refrigerant piping shafts, Sections 1105.7 and 1109.3.2.

8.9. Mechanical exhaust discharge for A2, B2, A3, and B3 refrigerant piping shafts, Sections 1105.7 and 1109.3.2.

501.4 Pressure equalization. Mechanical exhaust systems shall be sized to remove the quantity of air required by this chapter to be exhausted. The system shall operate when air is required to be exhausted. Where mechanical exhaust is required in a room or space, such space shall be maintained with a neutral or negative pressure. If a greater quantity of air is supplied by a mechanical ventilating supply system than is removed by a mechanical exhaust for a room, adequate means shall be provided for the natural or mechanical exhaust of the excess air supplied. If only a mechanical exhaust system is installed for a room or if a greater quantity of air is removed by a mechanical exhaust system than is supplied by a mechanical ventilating supply system for a room, adequate makeup air consisting of supply air, transfer air or outdoor air shall be provided to satisfy the deficiency. The calculated building infiltration rate shall not be used to satisfy the requirements of this section.

EXCEPTION:

Intermittent kitchen exhaust, intermittent domestic dryer exhaust, and intermittent local exhaust systems in R-3 occupancies and dwelling units in R-2 occupancies are excluded from the pressure equalization requirement unless required by Section 504 or Section 505.

WAC 51-52-0512Section 512—Wiring.

512.12.2 Wiring. In addition to meeting requirements of NFPA 70, all wiring, regardless of voltage used for circuits supplying detection and control functions shall be protected using one of the following methods:

1. Fully enclosed within continuous raceways.

2. Cables used for survivability of required critical circuits shall be listed in accordance with UL 2196 and shall have a fire-resistance rating of not less than one hour.

3. Electrical circuit protective systems shall have a fire-resistance rating of not less than one hour. Electrical circuit protective systems shall be installed in accordance with their listing requirements.

4. Construction having a fire-resistance rating of not less than one hour.

5. The cable is encased in a minimum of 2 inches (51 mm) of concrete.

AMENDATORY SECTION(Amending WSR 23-02-055, 23-12-106, and 23-20-025, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24)

WAC 51-52-0601Section 601—General.

601.2 Air movement in egress elements. Corridors shall not serve as supply, return, exhaust, relief or ventilation air ducts.

EXCEPTIONS:	1. Use of a corridor as a source of makeup air for exhaust systems in rooms that open directly onto such corridors, including toilet rooms, bathrooms, dressing rooms, smoking lounges and janitor closets, shall be permitted provided that each such corridor is directly supplied with outdoor air at a rate greater than the rate of makeup air taken from the corridor.
	2. Where located within a dwelling unit, the use of corridors for conveying return air shall not be prohibited.
	3. Where located within tenant spaces of one thousand square feet (93 m2) or less in area, utilization of corridors for conveying return air is permitted.
	4. Transfer air movement required to maintain pressurization difference within health care facilities in accordance with ASHRAE 170.
	5. Where such air is part of an engineered smoke control system.
	6. Air supplied to corridors serving residential occupancies shall not be considered as providing ventilation air to the dwelling units and sleeping units subject to the following:
	6.1 The air supplied to the corridor is one hundred percent outside air; and
	6.2 The units served by the corridor have conforming ventilation air independent of the air supplied to the corridor; and
	6.3 For other than high-rise buildings, the supply fan will automatically shut off upon activation of corridor smoke detectors installed in accordance with Section 606.2.4; or
	6.4 For high-rise buildings, the supply fan will automatically shut off upon activation of the smoke detectors required by International Fire Code Section 907.2.12.1 or upon receipt of another approved fire alarm signal. The supply fan is not required to be automatically shut off when used as part of an approved building stairwell or elevator hoistway pressurization system. Corridor smoke detectors shall be installed in accordance with Section 606.2.5.

601.5 Return air openings. Return air openings for heating, ventilation, and air-conditioning systems shall comply with all of the following:

1. Openings shall not be located less than 10 feet (3048 mm) measured in any direction from an open combustion chamber or draft hood of another appliance located in the same room or space.

2. Return air for heating or air-conditioning systems shall not be taken from a hazardous or insanitary location or a refrigeration room as defined in this code.

3. The amount of return air taken from any room or space shall be not greater than the flow rate of supply air delivered to such room or space.

4. Return and transfer openings shall be sized in accordance with the appliance or equipment manufacturer's installation instructions, ACCA Manual D or the design of the registered design professional.

5. Return air taken from one dwelling unit shall not be discharged into another dwelling unit.

6. Taking return air from a crawl space shall not be accomplished through a direct connection to the return side of a forced air furnace. Transfer openings in the crawl space enclosure shall not be prohibited.

7. Return air for heating or air-conditioning systems shall not be taken from a bathroom, toilet room, kitchen, garage, boiler room, furnace room, or unconditioned attic.

8. Return air from a closet shall serve only the closet and shall not require a dedicated closet supply duct.

9. Return air taken from a closet smaller than 30 square feet (2.8 m2) shall require the closet door be undercut not less than 1 1/2 inches (38 mm) or have either a louvered door or an air transfer grille, each with a net free area of not less than 30 square inches (19,355 m2).

10. Return air for heating or air-conditioning systems shall not be taken from indoor swimming pool enclosures and associated deck areas.

EXCEPTIONS:	1. Where the air from such spaces is dehumidified in accordance with Section 403.2.1, Item 2.
	2. Dedicated HVAC systems serving only such spaces.

EXCEPTIONS:	1. Taking return air for heating or air-conditioning systems from a kitchen is not prohibited where such return air openings serve the kitchen and are located not less than 10 feet (3048 mm) from the cooking appliances.
	2. Taking return air for heating or air-conditioning systems from a kitchen is not prohibited in a dwelling unit where the kitchen and living spaces are in a single room and the cooking appliance is electric and located not less than 5 feet (1524 mm) in any direction from the return air intake opening.
	3. Dedicated forced air systems serving only the garage shall not be prohibited from obtaining return air from the garage.
	4. Return air to nonrecirculating air distribution systems, such as an energy recovery ventilator, where the return air is discharged to the outdoors shall not be prohibited from obtaining return air from a bathroom, toilet room, kitchen, garage, boiler room, furnace room, or closet.

AMENDATORY SECTION(Amending WSR 23-02-055, 23-12-106, and 23-20-025, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24)

WAC 51-52-1101((Reserved.))General.

1101.1.1 Refrigerants other than ammonia. Refrigeration systems using a refrigerant other than ammonia shall comply with this chapter, the International Fire Code, and either ASHRAE 15 or ASHRAE 15.2, as applicable. Refrigeration systems containing carbon dioxide as the refrigerant shall also comply with IIAR CO2 or be part of listed and labeled equipment.

Table 1101.2 Factory-built equipment and appliances

EQUIPMENT	STANDARDS

Air-conditioning equipment	UL 1995 or UL/CSA 60335-2-40
Packaged terminal air conditioners and heat pumps	UL 484 or UL/CSA 60335-2-40
Split-system air conditioners and heat pumps	UL 1995 or UL/CSA 60335-2-40
Dehumidifiers	UL 474 or UL/CSA 60335-2-40
Unit coolers	UL 412 or UL/CSA 60335-2-89
Commercial refrigerators, freezers, beverage coolers, and walk-in coolers	UL 471 or UL/CSA 60335-2-89
Refrigerating units and walk-in coolers	UL 427 or UL 60335-2-89
Refrigerant-containing components and accessories	UL 207

1101.2.1 Group A2L, A2, A3, and B1 high-probability equipment. High-probability equipment using Group A2L, A2, A3, or B1 refrigerant shall comply with UL 484, UL/CSA 60335-2-40 or UL/CSA 60335-2-89.

EXCEPTIONS:

1. Factory-built low-probability equipment Group A3 using natural hydrocarbon refrigerants which are listed on a Northwest Energy Efficiency Alliance Qualified Product List are an acceptable alternative to the standards list in Table 1101.2. Such equipment is deemed to meet the design, manufacture, and factory test requirements of this code if installed in accordance with its listing and the manufacturer's instructions.

2. Listed and labeled factory-built low-probability equipment using Group A3 natural hydrocarbon refrigerants certified by an accredited third party to comply with IEC 60335-2-40 as an alternative to the list in Table 1101.2. Such equipment is deemed to meet the design, manufacture, and factory test requirements of this code if installed in accordance with its listing and the manufacturer's instructions.

WAC 51-52-1103Section 1103—Refrigeration system classification.

1103.1 Refrigerant classification. Refrigerants shall be classified in accordance with ASHRAE 34 as listed in Table 1103.1. Refrigerants without a refrigerant number designation or without a safety group classification in the referenced edition of ASHRAE 34 shall be classified in accordance with the criteria in ASHRAE 34 as a single-compound refrigerant blend of two or more compounds. Such safety classifications not assigned by ASHRAE 34 shall be submitted for approval to the code official. Compliance with the requirements of this code is contingent upon use of approved safety classifications where not assigned by the referenced edition of ASHRAE 34.

WAC 51-52-1104Section 1104—Refrigeration system application requirements.

1104.2 Machinery room. Except as provided in Sections 1104.2.1 and 1104.2.2, all components containing the refrigerant shall be located either outdoors or in a machinery room where the quantity of refrigerant in an independent circuit of a refrigeration system exceeds both of the following:

1. The amounts shown in Table 1103.1; and

2. The effective dispersal volume charge as calculated in accordance with ASHRAE 15.

For refrigerant blends not listed in Table 1103.1, the same requirement shall apply for that component. These requirements shall also apply where the combined amount of the blend components exceeds a limit of 69,100 parts per million (ppm) by volume. Machinery rooms required by this section and containing only Group A1 or B1 refrigerants shall be constructed and maintained in accordance with Section 1105. Machinery rooms required by this section and containing any Group A2, B2, A3, or B3 flammable refrigerants shall be constructed and maintained in accordance with Sections 1105 and 1106. Machinery rooms required by this section and containing any Group A2L or B2L flammable refrigerants and containing no Group A2, B2, A3, or B3 flammable refrigerants shall be constructed and maintained in accordance with Section 1105 and Sections 1106.4.1 through 1106.4.3.

EXCEPTIONS:	1. Machinery rooms are not required for listed equipment and appliances containing not more than 6.6 pounds (3 kg) of refrigerant, regardless of the refrigerant's safety classification, where installed in accordance with the equipment's or appliance's listing and the equipment or appliance manufacturer's installation instructions.
	2. Piping in compliance with Section 1107 is allowed in other locations to connect components installed in a machinery room with those installed outdoors.

1104.3.1 High-probability air conditioners, heat pumps, and dehumidifiers. High-probability air conditioners, heat pumps, and dehumidifiers shall use Group A1 or A2L refrigerant.

EXCEPTIONS:	1. Equipment listed for and used in residential occupancies containing a maximum of 6.6 pounds (3 kg) of refrigerant.
	2. Equipment listed for and used in commercial occupancies containing a maximum of 22 pounds (10 kg) of refrigerant.
	3. Industrial occupancies.

1104.3.2 Group A2, A3, B2, and B3 refrigerants. Group A2 and B2 refrigerants shall not be used in high-probability systems. Group A3 and B3 refrigerants shall not be used except where approved.

EXCEPTIONS:	1. Laboratories where the floor area per occupant is not less than 100 square feet (9.3 m2).
	2. Listed self-contained systems having a maximum of 0.331 pounds (150 g) of Group A3 refrigerant.
	3. Industrial occupancies.
	4. Equipment listed for and used in residential occupancies containing a maximum of 6.6 pounds (3 kg) of Group A2 or B2 refrigerant.
	5. Equipment listed for and used in commercial occupancies containing a maximum of 22 pounds (10 kg) of Group A2 or B2 refrigerant.
	6. Self-contained equipment using Groups A3 and B3 refrigerants that are listed to UL 60335-2-89 and installed in accordance with the listing, the manufacturer's installation instructions, and ASHRAE 15.
	7. Self-contained equipment using Groups A3 and B3 refrigerants that are listed to UL 60335-2-40 and installed in accordance with the listing, the manufacturer's installation instructions, and ASHRAE 15.

TABLE 1104.3.2

MAXIMUM PERMISSIBLE QUANTITIES OF REFRIGERANTS

EXCEPTION:	This section does not apply to:
	1. Laboratories where the floor area per occupant is not less than 100 square feet (9.3 m2).
	2. Listed self-contained systems having a maximum of 0.331 pounds (150 g) of Group A3 refrigerant.
	3. Industrial occupancies.
	4. Equipment listed for and used in residential occupancies containing a maximum of 6.6 pounds (3 kg) of Group A2 or B2 refrigerant.
	5. Equipment listed for and used in commercial occupancies containing a maximum of 22 pounds (10 kg) of Group A2 or B2 refrigerant.
	6. Self-contained equipment using Groups A3 and B3 refrigerants that are listed to UL 60335-2-89 and installed in accordance with the listing, the manufacturer's installation instructions, and ASHRAE 15.
	7. Self-contained equipment using Groups A3 and B3 refrigerants that are listed to UL 60335-2-40 and installed in accordance with the listing, the manufacturer's installation instructions, and ASHRAE 15.
	8. This restriction for A3 and B3 refrigerants does not apply to refrigeration systems located in machinery rooms or outdoors.
	9. Factory built low-probability equipment located in machinery rooms or outdoors containing a maximum of 10.8 pounds (4.9 kg) of Group A3 or B3 refrigerant.

1104.3.5 Corridors and lobbies. Refrigerating systems in a public corridor or lobby shall comply with ASHRAE 15 Section 7.5.1.2.

AMENDATORY SECTION(Amending WSR 23-02-055, 23-12-106, and 23-20-025, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24)

WAC 51-52-1105((Reserved.))Section 1105—Machinery room, general requirements.

1105.7 Termination of relief devices and refrigerant piping shaft ventilation discharge air outlets. Pressure relief devices, fusible plugs, and purge systems located within the machinery room and refrigerant piping shaft natural and mechanical ventilation discharge air shall terminate outside of the building and comply with all of the following:

1. The point of vent discharge shall be at a location not less than 15 feet (4572 mm) above the adjoining grade level.

2. The point of vent discharge shall be not less than 20 feet (6096 mm) from any window, ventilation opening, or exit.

3. For heavier-than-air refrigerants, the point of vent discharge shall be located not less than 20 feet (6096 mm) horizontally from below-grade walkways, entrances, pits, or ramps if a release of the entire system charge into such a space would yield a concentration of refrigerant in excess of the refrigerant concentration limit (RLC). The direct discharge of a relief vent into enclosed outdoor spaces, such as a courtyard with walls on all sides, shall not be permitted if a release of the entire system charge into such a space would yield a concentration of refrigerant in excess of the RLC. The volume for the refrigerant concentration calculation shall be determined using the gross area of the space and a height of 8.2 feet (2500 mm), regardless of the actual height of the enclosed space.

4. The termination point of a vent discharge line shall be made in a manner that prevents discharged refrigerant from spraying directly onto personnel that might be in the vicinity.

5. The termination point of vent discharge lines shall be made in a manner that prevents foreign material or debris from entering the discharge outlet.

6. Relief vent lines that terminate vertically upward and are subject to moisture entry shall be provided with a drip pocket having a minimum of 24 inches (610 mm) in length and having the size of the vent discharge pipe. The drip pocket shall be installed to extend below the first change in vent pipe direction and shall be fitted with a valve or drain plug to permit removal of accumulated moisture.

AMENDATORY SECTION(Amending WSR 23-23-105, filed 11/15/23, effective 3/16/24)

WAC 51-52-1106Section 1106—Machinery room, special requirements.

1106.3 Class 2 and 3 refrigerants. Where any flammable refrigerants of Groups A2, A3, B2, and B3 are used, the machinery room shall conform to the Class I, Division 2, hazardous location classification requirements of NFPA 70.

1106.4 Group A2L and B2L refrigerants.Machinery rooms containing any Group A2L or B2L refrigerants and containing no refrigerants of Group A2, A3, B2, or B3 shall comply with Sections 1106.4.1 through 1106.4.3.

1106.4.1 Elevated temperatures. Open flame-producing devices or continuously operating hot surfaces over 1290°F (700°C) shall not be permanently installed in the room.

1106.4.2 ((Emergency ventilation system. An emergency ventilation system shall be provided at the minimum exhaust rate specified in ASHRAE 15 or Table 1106.4.2. Shutdown of the emergency ventilation system shall be by manual means.))

Refrigerant detector. In addition to the requirements of Section 1105.3, refrigerant detectors shall signal an alarm and activate the ventilation system in accordance with the response time specified in Table 1106.4.2.

Table 1106.4.2

((MINIMUM EXHAUST RATES

Refrigerant	Q(m/sec)	Q(cfm)
R32	15.4	32,600
R143A	13.6	28,700
R444A	6.46	13,700
R444B	10.6	22,400
R445A	7.83	16,600
R446A	23.9	50,700
R447A	23.8	50,400
R451A	7.04	15,000
R451B	7.05	15,000
R1234yf	7.80	16,600
R1234ze(E)	5.92	12,600))

GROUP A2L AND B2L DETECTOR ACTIVATION

ACTIVATION LEVEL	MAXIMUM RESPONSE TIME (seconds)	ASHRAE 15 VENTILATION (seconds)	ALARM RESET	ALARM TYPE
Less than or equal to the OEL in Table 1103.1	300	1	Automatic	Trouble
Less than or equal to the refrigerant concentration level in Table 1103.1	15	2	Manual	Emergency

1106.4.3 Mechanical ventilation. The machinery room shall have a mechanical ventilation system complying with ASHRAE 15.

AMENDATORY SECTION(Amending WSR 20-03-041, filed 1/8/20, effective 7/1/20)

WAC 51-52-1107Section 1107—((Reserved.))Piping material.

1107.4 Piping materials standards. Refrigerant pipe shall conform to one or more of the standards listed in Table 1107.4. For refrigeration systems complying with ASHRAE 15.2 used in residential occupancies serving only a single dwelling unit or sleeping unit, refrigerant piping and tubing shall be limited to aluminum, copper, and copper alloy. The exterior of the pipe shall be protected from corrosion and degradation.

1107.5 Pipe fittings. Refrigerant pipe fittings shall be approved for installation with the piping materials to be installed, and shall conform to one or more of the standards listed in Table 1107.5 or shall be listed and labeled as complying with UL 207. For refrigeration systems complying with ASHRAE 15.2 used in residential occupancies serving only a single dwelling unit or sleeping unit, refrigerant fittings shall be limited to aluminum, copper, copper alloys, stainless steel, and steel.

WAC 51-52-1109Section 1109—Refrigerant pipe installation.

1109.2.2 Refrigerant pipe enclosure. Refrigerant piping shall be protected by locating it within the building elements or within protective enclosures.

EXCEPTION:	Piping protection within the building elements or protective enclosure shall not be required in any of the following locations:
	1. Where installed without ready access or located more than 7 feet 3 inches (2210 mm) above the finished floor.
	2. Where located within 6 feet (1829 mm) of the refrigerant unit or appliance.
	3. Where located in a machinery room complying with Section 1105.
	4. Outside the building:
	4.1. Where protected from damage from the weather including, but not limited to, hail, ice, and snow loads.
	4.2. Where protected from damage within the expected foot or traffic path.
	4.3. Where installed underground not less than 8 inches (200 mm) below finished grade and protected against corrosion.

1109.2.5 Refrigerant pipe shafts. Refrigerant piping that penetrates two or more floor/ceiling assemblies shall be enclosed in a fire-resistance-rated shaft enclosure. The fire-resistance-rated shaft enclosure shall comply with Section 713 of the International Building Code. Refrigerant pipe shafts that are naturally or mechanically ventilated shall be constructed as exterior building envelope walls with thermal insulation and air barrier construction required by the Washington state Energy Code.

EXCEPTIONS:	1. Refrigeration systems using R-718 refrigerant (water).
	2. Piping in a direct refrigeration system where the refrigerant quantity does not exceed the limits of Table 1103.1 for the smallest occupied space through which the piping passes.
	3. Piping located on the exterior of the building where vented to the outdoors. Natural ventilation openings shall be distributed vertically along the enclosure to prevent containment of refrigerant piping leaks and be located a minimum of 3 feet (914 mm) from operable openings into the building. Mechanical ventilation of exterior enclosures to comply with Section 1109.3.2.

1109.2.7 Pipe identification. Refrigerant pipe located in areas other than the room or space where the refrigerating equipment is located shall be identified. The pipe identification shall be located at intervals not exceeding 20 feet (6096 mm) on the refrigerant piping or pipe insulation. The minimum height of lettering of the identification label shall be 1/2 inch (12.7 mm). The identification shall indicate the refrigerant designation and safety group classification of the refrigerant used in the piping system. For Groups A2L and B2L refrigerants, the identification shall also include the following statement: "WARNING-Risk of Fire. Flammable Refrigerant." For Groups A2, A3, B2 and B3 refrigerants, the identification shall also include the following statement: "DANGER-Risk of Fire or Explosion. Flammable Refrigerant." For any Group B refrigerant, the identification shall also include the following statement: "DANGER-Toxic Refrigerant."

EXCEPTION:

For refrigeration systems complying with ASHRAE 15.2 used in residential occupancies serving only a single dwelling unit or sleeping unit, pipe identification shall not be required.

1109.3.2 Shaft ventilation. Refrigerant pipe shafts with systems using Group A2L or B2L refrigerant shall be naturally or mechanically ventilated. The shaft natural ventilation discharge outlet and mechanical ventilation discharge exhaust outlet shall comply with Sections 501.3.1 and 1105.7. Naturally ventilated shafts shall have a pipe, duct, or conduit not less than 4 inches (102 mm) in diameter that connects to the lowest point of the shaft and extends to the outdoors. The pipe, duct, or conduit shall be level or pitched downward to the outdoors. A makeup air opening shall be provided at the top of the shaft. Mechanically ventilated shafts shall have a minimum airflow velocity in accordance with Table 1109.3.2. The mechanical ventilation shall be continuously operated or activated by a refrigerant detector. Makeup air shall be provided at the inlet to the shaft for mechanically ventilated shafts. Systems utilizing a refrigerant detector shall activate the mechanical ventilation at a maximum refrigerant concentration of 25 percent of the lower flammable limit of the refrigerant. The detector, or a sampling tube that draws air to the detector, shall be located in an area where refrigerant from a leak will concentrate.

EXCEPTIONS:	1. The shaft shall not be required to be ventilated for double-wall refrigerant pipe where the interstitial space of the double-wall pipe is vented to the outdoors.
	2. For refrigeration systems complying with ASHRAE 15.2 used in residential occupancies serving only a single dwelling unit or sleeping unit, shaft ventilation shall not be required where the pipe or tube is continuous without fittings in the shaft.

1109.4.2 Shaft ventilation. Refrigerant pipe shafts with one or more systems using any Group A2, A3, B2, or B3 refrigerant shall be continuously mechanically ventilated and shall include a refrigerant detector. The shaft ventilation exhaust outlet shall comply with Sections 501.3.1 and 1105.7. Mechanically ventilated shafts shall have a minimum airflow velocity as specified in Table 1109.3.2. Makeup air shall be provided at the inlet to the shaft for mechanically ventilated shafts. The shaft shall not be required to be ventilated for double-wall refrigerant pipe where the interstitial space of the double-wall pipe is vented to the outdoors.

WAC 51-52-1110Section 1110—Refrigerant piping system test.

1110.2 Exposure of refrigerant piping system. Refrigerant pipe and joints installed in the field shall be exposed for visual inspection and testing prior to being covered or enclosed.

EXCEPTION:

Factory-insulated refrigerant piping line-sets are exempt from exposing the piping material for visual inspection.

AMENDATORY SECTION(Amending WSR 23-02-055, 23-12-106, and 23-20-025, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24)

WAC 51-52-1500Chapter 15—Referenced standards.

The following referenced standards are amended or added to Chapter 15.

AHAM

Association of Home Appliance Manufacturers

1111 19th St. N.W., #402

Washington D.C. 20036

AHAM-Certified Range Hood

Directory. . . .403.4.7.3.1

HRH-2 Household Range Hoods . . . .403.4.7.3.1

ANCE

UL/CSA/ANCE 60335-2-40—((2019))2022 Household and Similar Electrical Appliances - Safety - Part 2-40: Particular Requirements for Electrical Heat Pumps, Air Conditioners and

Dehumidifiers . . . .1101.2

ASHRAE

15-2022 Safety Standard for Refrigeration

Systems . . . .1101.6,1104.3.5, 1105.8, 1106.4.2, 1108.1

15.2-2022 Safety Standard for Refrigeration Systems in Residential Applications . . . .1101.1.1, 1107.4, 1107.5, 1109.2.7, 1109.3.2

34-2022 Designation and Safety Classification of

Refrigerants . . . .202, 1102.2.1, 1103.1

62.2-((2019))2022 Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings . . . .401.4, 403.4, 403.4.7.3.3,

403.4.11

ASTM

E3087—18: Standard Test Method for Measuring Capture Efficiency of Domestic Range Hoods . . . .403.4.7.3.2, Table 403.4.7.3.2

CSA

UL/CSA/ANCE 60335-2-40—((2019))2022 Household and Similar Electrical Appliances - Safety - Part 2-40: Particular Requirements for Electrical Heat Pumps, Air Conditioners and

Dehumidifiers. . . .1101.2

HVI address:

Home Ventilating Institute

1740 Dell Range Blvd., Suite H, PMB 450

Cheyenne, WY 82009

HVI Publication 911 Certified Home Ventilating Product

Directory . . . .403.4.7.3.4

HVI 915-2020 Procedure for Loudness Testing of Residential Fan Products. . . .403.4.6.1, 403.4.6.2, 403.4.7.2

HVI 916-2020 Air Flow Test Procedure. . . .403.4.6.1,

403.4.6.2, 403.4.7.2

HVI 920-2020 Product Performance Certification and Surveillance Procedure ((Including Verification and Challenge))

. . . .403.4.6.1, 403.4.6.2, 403.4.7.2

NFPA

110-22 Standard for Emergency and Standby Power

Systems . . . .915.3, 915.3.1, 915.3.2

111-22 Standard on Stored Electrical Energy Emergency and Standby Power Systems . . . .915.3, 915.4

864-2014 Control Units and Accessories for Fire Alarm Systems with revisions through

October 2018. . . .606.2.2

UL/CSA/ANCE 60335-2-40—((2019))2022 Household and Similar Electrical Appliances - Safety - Part 2-40: Particular Requirements for Electrical Heat Pumps, Air Conditioners and

Dehumidifiers. . . .1101.2

WAC 51-52-21114Section 114 (IFGC)—Failure to comply.

114.4 (IFGC)—Failure to comply. Any person who shall continue any work after having been served with a stop work order, except such work as that person is directed to perform to remove a violation or unsafe condition, shall be subject to fines established by the code official authority having jurisdiction.