WSR 04-17-018



[ Filed August 9, 2004, 9:16 a.m. ]

Original Notice.

Preproposal statement of inquiry was filed as WSR 04-13-075.

Title of Rule and Other Identifying Information: Chapter 51-52 WAC, State adoption and amendment of the 2003 International Mechanical Code, Sections 401.5.2, 403.3 and 501.5.

Hearing Location(s): Renton, Holiday Inn Select, One Grady Way South, Renton, WA, on October 15, 2004, at 10:00 a.m.

Date of Intended Adoption: November 12, 2004.

Submit Written Comments to: Stan Price, Chairman, State Building Code Council, P.O. Box 42525, Olympia, WA 98504-2525, e-mail, fax (360) 586-9383, by October 15, 2004.

Assistance for Persons with Disabilities: Contact Sue Mathers by October 1, 2004, TTY (360) 753-7427 or (360) 725-2967.

Purpose of the Proposal and Its Anticipated Effects, Including Any Changes in Existing Rules: The purpose of the proposed rule is to amend chapter 51-52 WAC that adopts the 2003 International Mechanical Code (IMC). The anticipated effects include achieving improved compliance with state mechanical code provisions for the benefit [of] public health, safety and welfare, and to serve Washington state interests.

The proposed amendments include language that will correct a deficiency in the IMC by providing clear explicit rules for mechanical exhaust duct termination points. This change will provide clarification of current practice and provide flexibility for the benefit of industry.

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: Chapters 19.27 and 34.05 RCW.

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

Name of Proponent: State Building Code Council, governmental.

Name of Agency Personnel Responsible for Drafting and Implementation: Al Rhoades, Olympia, Washington 98504-2525, (360) 725-2970; and Enforcement: Local jurisdictions.

No small business economic impact statement has been prepared under chapter 19.85 RCW. This rule provides clarification of existing national standards and current practice for the benefit of industry and Washington state interests. No economic impact on small business was identified.

A cost-benefit analysis is not required under RCW 34.05.328. This rule clarifies code requirements and does not affect cost.

August 6, 2004

Tim Nogler

for Stan Price



Chapter 51-52 WAC



WAC 51-52-0401   Section 401 -- General.  

401.5.2 Exhaust openings. Outdoor exhaust openings shall be located in accordance with Chapter 5. Exhaust air shall not be directed onto walkways.


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

403.3 Ventilation rate. Ventilation systems shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with Table 403.3 based on the occupancy of the space and the occupant load or other parameter as stated therein. 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. Ventilation rates for occupancies not represented in Table 403.3 shall be determined by an approved engineering analysis. The ventilation system 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.

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 estimated maximum occupancy rates.


WAC 51-52-0501   Section 501 -- General.  

501.5 Termination point/exhaust outlet. The termination point or exhaust outlet for exhaust ducts discharging to the atmosphere 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 openings into the building; 6 feet (1829 mm) from exterior walls and roofs; 30 feet (9144 mm) from combustible walls and 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 the property line; 3 feet (914 mm) from exterior walls and roofs; 10 feet (3048 mm) from openings into the building; 10 feet (3048 mm) above adjoining grade.

3. For environmental air duct exhaust: 3 feet (914 mm) from the property line, 3 feet (914 mm) from openings into the building for all occupancies other that Group U, and 10 feet (3048 mm) from a mechanical air intake. This includes environmental air regulated by Sections 504 and 505, but does not include enclosed parking garage exhaust outlets regulated by Section 404.

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.


Legislature Code Reviser 


Washington State Code Reviser's Office