PDFWAC 51-52-0605

Section 605—Air filters.

605.1 General. Air handlers and ventilation systems shall be provided with approved air filters in accordance with Section 605.4. Filters shall be installed such that all return air, recirculated air, outdoor air and makeup air is filtered upstream from any heat exchanger or coil. Filters shall be installed in an approved convenient location. Liquid adhesive coatings used on filters shall have a flash point not lower than 325°F (163°C).
EXCEPTIONS:
1. Cooling coils that are designed, controlled and operated to provide sensible cooling only do not require filtration at the terminal device.
 
2. Ambient air that enters the building through intentional openings for natural ventilation or by infiltration is not required to be filtered.
 
3. Recirculated air serving systems without wetted cooling coils or with unducted heater (hydronic coils, fossil fuel heating elements or electric resistance heating elements) do not require filtration at the terminal device.
605.4 Particulate matter removal. Particulate matter filters or air cleaners shall have a minimum efficiency reporting value (MERV) of not less than the following:
1. MERV 13 for ducted air handlers and ventilation systems serving occupiable spaces in Groups A, B, E, M, R and I occupancies.
2. MERV 8 for ducted air handlers and ventilation systems serving occupiable spaces in Groups F, H, S, and U occupancies.
3. MERV 4 for unducted air handlers and fan coil units.
EXCEPTIONS:
1. Ducted air handlers and ventilation systems 500 cfm or less shall have a filter not less than MERV 8.
 
2. Recirculated air at fan powered variable air volume terminal units with hydronic heating coils or electric resistance heating elements shall have a filter not less than MERV 8.
 
3. Exhaust or relief air upstream of a heat exchanger or coil shall have a filter not less than MERV 6.
[Statutory Authority: RCW 19.27.031 and 19.27.074. WSR 23-02-055, 23-12-106, and 23-20-025, § 51-52-0605, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24; WSR 20-03-041, § 51-52-0605, filed 1/8/20, effective 7/1/20; WSR 16-01-148, § 51-52-0605, filed 12/21/15, effective 7/1/16. Statutory Authority: RCW 19.27.031, 19.27.074 and chapters 19.27 and 34.05 RCW. WSR 13-04-053, § 51-52-0605, filed 2/1/13, effective 7/1/13.]