Purpose: To amend the Washington state amendments to the 2003 International Mechanical Code to provide clear explicit rules for mechanical exhaust duct termination points.

     Citation of Existing Rules Affected by this Order: Amending [new sections] WAC 51-52-0401, 51-52-0403, and 51-52-0501.

     Statutory Authority for Adoption: RCW 19.27.020, 19.27.031, and 19.27.074.

     Other Authority: Chapters 19.27 and 34.05 RCW.

      Adopted under notice filed as WSR 04-17-018 on August 9, 2004.

     Number of Sections Adopted in Order to Comply with Federal Statute: New 0, Amended 0, Repealed 0; Federal Rules or Standards: New 0, Amended 0, Repealed 0; or Recently Enacted State Statutes: New 0, Amended 0, Repealed 0.

     Number of Sections Adopted at Request of a Nongovernmental Entity: New 0, Amended 3, Repealed 0.

     Number of Sections Adopted on the Agency's Own Initiative: New 0, Amended 0, Repealed 0.

     Number of Sections Adopted in Order to Clarify, Streamline, or Reform Agency Procedures: New 0, Amended 0, Repealed 0.

     Number of Sections Adopted Using Negotiated Rule Making: New 0, Amended 0, Repealed 0;      Pilot Rule Making: New 0, Amended 0, Repealed 0; or Other Alternative Rule Making: New 0, Amended 3, Repealed 0.

     Date Adopted: November 12, 2004.

Stan Price

Council Chair

OTS-7371.1

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

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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.

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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.

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