WAC 51-13-304   Mechanical ventilation criteria and minimum ventilation performance for all other occupancies not covered in sections 302 and 303.  


     304.1 Ventilation: The minimum requirements for operable area to provide natural ventilation are specified in the International Building Code (IBC) as adopted by the state of Washington.


     Where a mechanical ventilation system is installed, the mechanical ventilation system shall be capable of supplying ventilation air to each zone with the minimum outdoor air quantities specified in Table 3-4.


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 3-4 estimated maximum occupancy values.

     The outdoor air shall be ducted in a fully enclosed path directly to every air handling unit in each zone not provided with sufficient operable area for natural ventilation.


EXCEPTION: Ducts may terminate within 12 inches of the intake to an HVAC unit provided they are physically fastened so that the outside air duct is directed into the unit intake.

     In all parking garages, other than open parking garages as defined in IBC 406.3, used for storing or handling of automobiles operating under their own power and on all loading platforms in bus terminals, ventilation shall be provided at 1.5 cfm per square foot of gross floor area. The building official may approve an alternate ventilation system designed to exhaust a minimum fourteen thousand cfm for each operating vehicle. Such system shall be based on the anticipated instantaneous movement rate of vehicles but not less than 2.5 percent (or one vehicle) of the garage capacity. Automatic carbon monoxide sensing systems may be submitted for approval.


     In all buildings used for the repair of automobiles, each repair stall shall be equipped with an exhaust extension duct, extending to the outside of the building, which if over ten feet in length, shall mechanically exhaust three hundred cfm. Connecting offices and waiting rooms shall be supplied with conditioned air under positive pressure.


     Combustion air requirements shall conform to the requirements of Chapter 7 of the International Mechanical Code (IMC).


     Mechanical refrigerating equipment and rooms storing refrigerants shall conform to the requirements of Chapter 11 of the IMC.


     304.2 Alternate Systems: Alternate systems designed in accordance with ASHRAE Standard 62.1.2004 shall be permitted.

TABLE 3-1

Minimum Source Specific Ventilation Capacity

Requirements

  Bathrooms Kitchens
Intermittently operating 50 cfm 100 cfm
Continuous operation 20 cfm 25 cfm


TABLE 3-2

Ventilation Rates For All Group R Occupancies four (4) stories and less*

Minimum and Maximum Ventilation Rates: Cubic Feet Per Minute (CFM)
Floor

Area, ft2		 Bedrooms
2 or less 3 4 5 6 7 8
  Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max.
<500 50 75 65 98 80 120 95 143 110 165 125 188 140 210
501-1000 55 83 70 105 85 128 100 150 115 173 130 195 145 218
1001-1500 60 90 75 113 90 135 105 158 120 180 135 203 150 225
1501-2000 65 98 80 120 95 143 110 165 125 188 140 210 155 233
2001-2500 70 105 85 128 100 150 115 173 130 195 145 218 160 240
2501-3000 75 113 90 135 105 158 120 180 135 203 150 225 165 248
3001-3500 80 120 95 143 110 165 125 188 140 210 155 233 170 255
3501-4000 85 128 100 150 115 173 130 195 145 218 160 240 175 263
4001-5000 95 143 110 165 125 188 140 210 155 233 170 255 185 278
5001-6000 105 158 120 180 135 203 150 225 165 248 180 270 195 293
6001-7000 115 173 130 195 145 218 160 240 175 263 190 285 205 308
7001-8000 125 188 140 210 155 233 170 255 185 278 200 300 215 323
8001-9000 135 203 150 225 165 248 180 270 195 293 210 315 225 338
>9000 145 218 160 240 175 263 190 285 205 308 220 330 235 353
*For residences that exceed 8 bedrooms, increase the minimum requirement listed for 8 bedrooms by an additional 15 CFM per bedroom. The maximum CFM is equal to 1.5 times the minimum.

TABLE 3-3

Prescriptive Exhaust Duct Sizing

Fan Tested

CFM @

0.25 W.G.		 Minimum

Flex

Diameter		 Maximum

Length

Feet		 Minimum

Smooth

Diameter		 Maximum

Length

Feet		 Maximum

Elbows1
50 4 inch 25 4 inch 70 3
50 5 inch 90 5 inch 100 3
50 6 inch No Limit 6 inch No Limit 3
80 4 inch2 NA 4 inch 20 3
80 5 inch 15 5 inch 100 3
80 6 inch 90 6 inch No Limit 3
100 5 inch2 NA 5 inch 50 3
100 6 inch 45 6 inch No Limit 3
125 6 inch 15 6 inch No Limit 3
125 7 inch 70 7 inch No Limit 3

1. For each additional elbow subtract 10 feet from length.
2. Flex ducts of this diameter are not permitted with fans of this size.


TABLE 3-4

Outdoor air requirements for ventilation1

Occupancies not subject to sections 302 and 303

Application Estimated

Maximum2

Occupancy

P/1000 ft2 or

100 m2		 Outdoor Air

Requirements

cfm/person
Dry Cleaners, Laundries3
     Commercial laundry 10 25
     Commercial dry cleaner 30 30
     Storage, pick up 30 35
     Coin-operated laundries 20 15
     Coin-operated dry cleaner 20 15
Dwelling Units In Buildings Greater Than Four Stories or Attached to I-

     Occupancy Facilities
     Bedroom & living area24   15
Food and Beverage Service
     Dining rooms 70 20
     Cafeteria, fast food 100 20
     Bars, cocktail lounges4 100 30
     Kitchens (cooking)23 20 15
Garages, Repair, Service Stations
     Enclosed parking garage5   1.50 cfm/ft.sq.
     Auto repair rooms   1.50 cfm/ft.sq.
Hotels, Motels, Resorts, Congregate Residences with More Than Four

     Stories6
     Bedrooms   30 cfm/room
     Living Rooms   30 cfm/room
     Bath7   35 cfm/room
     Lobbies 30 15
     Conference rooms 50 20
     Assembly rooms 120 15
     Gambling casinos4 120 30
Offices
     Office space9 7 20
     Reception area 60 15
     Telecommunication

     centers and data

     entry areas		 60 20
     Conference rooms 50 20
Public Spaces
     Corridors and utilities   0.05 cfm/ft.sq.
     Public restroom, cfm/wc

     or urinal10		   50
     Lockers and dressing rooms   0.50 cfm/ft.sq.
     Smoking lounge11 70 60
     Elevators12   1.0 cfm/ft.sq.
Retail Stores, Sales Floors, and Show Room Floors
     Basement and street 30 0.30 cfm/ft.sq.
     Upper floors 20 0.20 cfm/ft.sq.
     Storage rooms 15 0.15 cfm/ft.sq.
     Dressing rooms   0.20 cfm/ft.sq.
     Malls and arcades 20 0.20 cfm/ft.sq.
     Shipping and receiving 10 0.15 cfm/ft.sq.
     Smoking lounge11 70 60
     Warehouses 5 0.05 cfm/ft.sq.
Speciality Shops
     Barber 25 15
     Beauty 25 25
     Reducing salons 20 15
     Florists13 8 15
     Clothiers, furniture   0.30 cfm/ft.sq.
     Hardware, drugs, fabric 8 15
     Supermarkets 8 15
     Pet shops   1.00 cfm/ft.sq.
Sports and Amusement14
     Spectator areas 150 15
     Game rooms 70 25
     Ice arenas (playing areas)   0.50 cfm/ft.sq.
     Swimming Pools (pool

     and deck area)15		   0.50 cfm/ft.sq.
     Playing floor (gymnasium) 30 20
     Ballrooms and discos 100 25
     Bowling alleys (seating areas) 70 25
Theaters16
     Ticket booths 60 20
     Lobbies 150 20
     Auditorium 150 20
     Stages, studios 70 15
Transportation17
     Waiting rooms 100 15
     Platforms 100 15
     Vehicles 150 15
Workrooms
     Meat processing18 10 15
     Photo studios 10 15
     Darkrooms 10 0.50 cfm/ft.sq.
     Pharmacy 20 15
     Bank vaults 5 15
     Duplicating, printing19   0.50 cfm/ft.sq.
INSTITUTIONAL FACILITIES
Education
     Classroom 50 15
     Laboratories20 30 20
     Training shop 30 20
     Music rooms 50 15
     Libraries 20 15
     Locker rooms   0.50 cfm/ft.sq.
     Corridors   0.10 cfm/ft.sq.
     Auditoriums 150 15
     Smoking lounges11 70 60
Hospitals, Nursing and Convalescent Homes
     Patient rooms21 10 25
     Medical procedure 20 15
     Operating rooms 20 30
     Recovery and ICU 20 15
     Autopsy rooms22   0.50 cfm/ft.sq.
     Physical Therapy 20 15
Correctional Facilities
     Cells 20 20
     Dining halls 100 15
     Guard station 40 15


1. Derived from ASHRAE Standard 62-1989.
2. Net occupiable space.
3. Dry-cleaning process may require more air.
4. Supplementary smoke-removal equipment may be required.
5. Distribution among people must consider worker location and concentration of running engine; stands where engines are run must incorporate systems for positive engine exhaust withdrawal. Contaminant sensors may be used to control ventilation.
6. Independent of room size.
7. Installed capacity for intermittent use.
8. See also food and beverage service, merchandising, barber and beauty shops, garages.
9. Some office equipment may require local exhaust.
10. Mechanical exhaust with no recirculation is recommended.
11. Normally supplied by transfer air, local mechanical exhaust; with no recirculation recommended.
12. Normally supplied by transfer air.
13. Ventilation to optimize plant growth may dictate requirements.
14. When internal combustion engines are operated for maintenance of playing surfaces, increased ventilation rates may be required.
15. Higher values may be required for humidity control.
16. Special ventilation will be needed to eliminate special stage effects.
17. Ventilation within vehicles may require special considerations.
18. Spaces maintained at low temperatures (-10°F. to + 50°F.) are not covered by these requirements unless the occupancy is continuous. Ventilation from adjoining spaces is permissible. When the occupancy is intermittent, infiltration will normally exceed the ventilation requirements.
19. Installed equipment must incorporate positive exhaust and control of undesirable contaminants.
20. Special contamination control systems may be required for processes or functions including laboratory animal occupancy.
21. Special requirements or codes and pressure relationships may determine minimum ventilation rates and filter efficiency. Procedures generating contaminants may require higher rates.
22. Air shall not be recirculated into other spaces.
23. Makeup air for hood exhaust may require more ventilating air.
24. Occupant loading shall be based on the number of bedrooms as follows: first bedroom, two persons; each additional bedroom, one person. Where higher occupant loadings are known, they shall be used.
TABLE 3-5

Prescriptive Integrated Forced Air Supply Duct Sizing

Required

Flow

(CFM) Per

Table 3-2		 Minimum

Smooth

Duct

Diameter		 Minimum

Flexible

Duct

Diameter		 Maximum

Length1		 Maximum

Number of

Elbows2
50-80 6" 7" 20' 3
80-125 7" 8" 20' 3
115-175 8" 10" 20' 3
170-240 9" 11" 20' 3

1. For lengths over 20 feet increase duct diameter 1 inch.
2. For elbows numbering more than 3 increase duct diameter 1 inch.

TABLE 3-6

Prescriptive Supply Fan Duct Sizing
Supply Fan Tested CFM At 0.4" WG
Specified

volume

from Table 3-2		 Minimum

Smooth

Duct Diameter		 Minimum

Flexible

Duct Diameter
50-90 CFM 4 inch 5 inch
90-150 CFM 5 inch 6 inch
150-250 CFM 6 inch 7 inch
250-400 CFM 7 inch 8 inch




[Statutory Authority: RCW 19.27.190, 19.27.020 and chapters 19.27 and 34.05 RCW. 07-01-095, § 51-13-304, filed 12/19/06, effective 7/1/07; 04-07-192, § 51-13-304, filed 3/24/04, effective 7/1/04. Statutory Authority: RCW 19.27.190, 19.27.020. 01-02-099, § 51-13-304, filed 1/3/01, effective 7/1/01. Statutory Authority: RCW 19.27.190. 95-01-128, § 51-13-304, filed 12/21/94, effective 6/30/95. Statutory Authority: RCW 19.27.190(2) and 1992 c 132. 93-02-056, § 51-13-304, filed 1/6/93, effective 7/1/93. Statutory Authority: RCW 19.27.190. 91-01-102, § 51-13-304, filed 12/18/90, effective 7/1/91.]