CODES

ADOPTS WITH AMENDMENTS:

International Mechanical Code 2015 (IMC 2015)

Copyright

Preface

Effective Use of the International Mechanical Code

Legislation

Chapter 1 Scope and Administration

Chapter 2 Definitions

Chapter 3 General Regulations

Chapter 4 Ventilation

Chapter 5 Exhaust Systems

Chapter 6 Duct Systems

Chapter 7 Combustion Air

Chapter 8 Chimneys and Vents

Chapter 9 Specific Appliances, Fireplaces and Solid Fuel-Burning Equipment

Chapter 10 Boilers, Water Heaters and Pressure Vessels

Chapter 11 Refrigeration

Chapter 12 Hydronic Piping

Chapter 13 Fuel Oil Piping and Storage

Chapter 14 Solar Systems

Chapter 15 Referenced Standards

Appendix A Chimney Connector Pass-Throughs

Appendix B Recommended Permit Fee Schedule

This chapter shall govern the ventilation of spaces within a building intended to be occupied. Mechanical exhaust systems, including exhaust systems serving clothes dryers and cooking appliances; hazardous exhaust systems; dust, stock and refuse conveyor systems; subslab soil exhaust systems; smoke control systems; energy recovery ventilation systems and other systems specified in Section 502 shall comply with Chapter 5.

401.2 Ventilation Required

STATE AMENDMENT
Every occupied space shall be ventilated by natural means in accordance with Section 402 or by mechanical means in accordance with Section 403. Where the air infiltration rate in a dwelling unit is less than 5 air changes per hour when tested with a blower door at a pressure of 0.2-inch water column (50 Pa) in accordance with Section R402.4.1.2 of the International Energy Conservation Code, the dwelling unit shall be ventilated by mechanical means in accordance with Section 403. Ambulatory care facilities and Group I-2 occupancies shall be ventilated by mechanical means in accordance with Section 407.
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 the repair of automobiles shall be ventilated by mechanical means in accordance with Sections 403 and 404.

401.2.1 Group R Occupancies

STATE AMENDMENT
Ventilation in Group R occupancies shall be provided in accordance with Section 403.8.
Ambulatory care facilities and Group I-2 occupancies shall be ventilated by mechanical means in accordance with Section 407.
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

STATE AMENDMENT
Group R occupancies shall be vented continuously or intermittently in accordance with Section 403.8. Ventilation in all other occupancies shall be provided during the periods that the room or space is occupied.
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.

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 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.

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.

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.
Air intake openings that terminate outdoors shall be protected with corrosion-resistant screens, louvers or grilles. Openings in louvers, grilles and screens shall be sized in accordance with Table 401.5, and shall be protected against local weather conditions. Louvers that protect air intake openings in structures located in hurricane-prone regions, as defined in the International Building Code, shall comply with AMCA 550. Outdoor air intake openings located in exterior walls shall meet the provisions for exterior wall opening protectives in accordance with the International Building Code.

TABLE 401.5 OPENING SIZES IN LOUVERS, GRILLES AND SCREENS PROTECTING AIR INTAKE OPENINGS

OUTDOOR OPENING TYPE MINIMUM AND MAXIMUM OPENING
SIZES IN LOUVERS, GRILLES AND
SCREENS MEASURED IN ANY
DIRECTION
Intake openings in
residential occupancies
Not < 1/4 inch and not > 1/2 inch
Intake openings in other
than residential occupancies
> 1/4 inch and not > 1 inch

For SI: 1 inch = 25.4 mm.
Stationary local sources producing air-borne particulates, heat, odors, fumes, spray, vapors, smoke or gases in such quantities as to be irritating or injurious to health shall be provided with an exhaust system in accordance with Chapter 5 or a means of collection and removal of the contaminants. Such exhaust shall discharge directly to an approved location at the exterior of the building.

401.7 Testing and Balancing

STATE AMENDMENT
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-transverse type measurement systems in the duct, short term tracer gas measurements, or other means approved by the building official.
Natural ventilation of an occupied space shall be through windows, doors, louvers or other openings to the outdoors. The operating mechanism for such openings shall be provided with ready access so that the openings are readily controllable by the building occupants.
The minimum openable area to the outdoors shall be 4 percent of the floor area being ventilated.
Where rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining rooms shall be unobstructed and shall have an area not less than 8 percent of the floor area of the interior room or space, but not less than 25 square feet (2.3 m2). The minimum openable area to the outdoors shall be based on the total floor area being ventilated.

Exception: Exterior openings required for ventilation shall be permitted to open into a thermally isolated sunroom addition or patio cover, provided that the openable area between the sunroom addition or patio cover and the interior room has an area of not less than 8 percent of the floor area of the interior room or space, but not less than 20 square feet (1.86 m2). The minimum openable area to the outdoors shall be based on the total floor area being ventilated.
Where openings below grade provide required natural ventilation, the outside horizontal clear space measured perpendicular to the opening shall be one and one-half times the depth of the opening. The depth of the opening shall be measured from the average adjoining ground level to the bottom of the opening.

403.1 Ventilation System

STATE AMENDMENT
Mechanical ventilation shall be provided by a method of supply air and return or exhaust air except that mechanical ventilation air requirements for Group R-2, R-3 and R-4 occupancies three stories and less in height above grade plane shall be provided by an exhaust system, supply system or combination thereof. 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

STATE AMENDMENT
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.
The outdoor 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 more than 10 percent or more of the resulting supply airstream consists of air recirculated from these spaces.
  3. Where mechanical exhaust is required by Note b in Table 403.3.1.1, recirculation of air from such spaces shall be prohibited. Recirculation of air that is contained completely within such spaces shall not be prohibited. Where recirculation of air is 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.
Except where recirculation from such spaces is prohibited by Table 403.3.1.1, air transferred from occupiable spaces is not prohibited from serving as makeup air for required exhaust systems in such spaces as kitchens, baths, toilet rooms, elevators and smoking lounges. The amount of transfer air and exhaust air shall be sufficient to provide the flow rates as specified in Section 403.3.1.1. The required outdoor airflow rates specified in Table 403.3.1.1 shall be introduced directly into such spaces or into the occupied spaces from which air is transferred or a combination of both.
Group R-2, R-3 and R-4 occupancies three stories and less in height above grade plane shall be provided with outdoor air and local exhaust in accordance with Section 403.3.2 403.8. All other buildings intended to be occupied shall be provided with outdoor air and local exhaust in accordance with Section 403.3.1.
The design of local exhaust systems and ventilation systems for outdoor air for occupancies other than Group R-2, R-3 and R-4 three stories and less above grade plane shall comply with Sections 403.3.1.1 through 403.3.1.5.
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. The occupant load utilized for design of the ventilation system shall be 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 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: The occupant load is not required to be determined based on the estimated maximum occupant load rate indicated in Table 403.3.1.1 where approved statistical data document the accuracy of an alternate anticipated occupant density. 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 MINIMUM VENTILATION RATES

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 0.06
Commercial dry cleaner 30 30
Commercial laundry 10 25
Storage, pick up 30 7.5 0.12
Education
Art classroomg 20 10 0.18 0.7
Auditoriums 150 5 0.06
Classrooms (ages 5-8) 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 0.7


(continued)

TABLE 403.3.1.1‒continued MINIMUM VENTILATION RATES

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
Hotels, motels, resorts and dormitories
Bathrooms/toilet‒privateg 25/50f
Bedroom/living room 10 5 0.06
Conference/meeting 50 5 0.06
Dormitory sleeping areas 20 5 0.06
Gambling casinos 120 7.5 0.18
Lobbies/prefunction 30 7.5 0.06
Multipurpose assembly 120 5 0.06
Offices
Conference rooms 50 5 0.06
Kitchenettesk 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 25/100f
Living areasc Based upon number
of bedrooms. First
bedroom, 2; each
additional bedroom,
1
0.35 ACH but not less
than 15 cfm/person
See Tables 403.8.1 and 403.8.5.1
Toilet rooms and bathrooms and laundry areasg,i 20/50f
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 0.6
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 shower head)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 0.12
Smoking loungesb 70 60
Storage rooms 0.12
Warehouses (see storage)


(continued)

TABLE 403.3.1.1‒continued MINIMUM VENTILATION RATES

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
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
Nail salons b, h 25 20 0.12 0.6
Embalming roomb 2.0
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 engines 0.30 0.5
Gym, stadium, arena (play area)j 0.30
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 garagesb,d 0.75
Storage rooms, chemical 1.5
Warehouses 0.06
Theaters
Auditoriums (see education)
Lobbies 150 0.06
Stages, studios 70 0.06
Ticket booths 60 5 0.06
Transportation
Platforms 100 7.5 0.06
Transportation waiting 100 7.5 0.06


(continued)

TABLE 403.3.1.1‒continued MINIMUM VENTILATION RATES

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
Workrooms
Bank vaults/safe deposit 5 5 0.06
Computer (without printing) 4 5 0.06
Copy, printing rooms 4 5 0.06 0.5
Darkrooms 1.0
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

For SI: 1 cubic foot per minute = 0.0004719 m3/s, 1 ton = 908 kg, 1 cubic foot per minute 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 except that recirculation shall be permitted where the resulting supply airstream consists of not more than 10 percent air recirculated from these spaces. 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 stations 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. A laundry area within a kitchen or bathroom is not required to have local exhaust. For the laundry area to qualify as being within the kitchen, the laundry room door must open directly into the kitchen and not into an adjacent corridor. Where there are doors that separate the laundry area from the kitchen or bathroom, the door shall be louvered.
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 507.2.2. Kitchenettes that only contain a microwave oven are not required to have mechanical exhaust. A kitchenette may not contain commercial cooking appliances that require Type 1 or Type II exhaust as these occupancies are required to be exhausted to the kitchen category in Table 403.3.1.1.
The minimum outdoor airflow required to be supplied to each zone shall be determined as a function of occupancy classification and space air distribution effectiveness in accordance with Sections 403.3.1.1.1.1 through 403.3.1.1.1.3.
The outdoor airflow rate required in the breathing zone (Vbz) of the occupiable space or spaces in a zone shall be determined in accordance with Equation 4-1.



where:

Az = Zone floor area: the net occupiable floor area of the space or spaces in the zone.
Pz = Zone population: the number of people in the space or spaces in the zone.
Rp = People outdoor air rate: the outdoor airflow rate required per person from Table 403.3.1.1.
Ra = Area outdoor air rate: the outdoor airflow rate required per unit area from Table 403.3.1.1.
The zone air distribution effectiveness (Ez) shall be determined using Table 403.3.1.1.1.2.

TABLE 403.3.1.1.1.2 ZONE AIR DISTRIBUTION EFFECTIVENESSa,b,c,d

AIR DISTRIBUTION CONFIGURATION Ez
Ceiling or floor supply of cool air 1.0e
Ceiling or floor supply of warm air and floor return 1.0
Ceiling supply of warm air and ceiling return 0.8f
Floor supply of warm air and ceiling return 0.7
Makeup air drawn in on the opposite side of the room from the exhaust and/or return 0.8
Makeup air drawn in near to the exhaust and/or return location 0.5

For SI: 1 foot = 304.8 mm, 1 foot per minute = 0.00506 m/s,°C =[(°F)‒ 32]/1.8.
a. "Cool air" is air cooler than space temperature.
b. "Warm air" is air warmer than space temperature.
c. "Ceiling" includes any point above the breathing zone.
d. "Floor" includes any point below the breathing zone.
e. Zone air distribution effectiveness of 1.2 shall be permitted for systems with a floor supply of cool air and ceiling return, provided that low- velocity displacement ventilation achieves unidirectional flow and thermal stratification.
f. Zone air distribution effectiveness of 1.0 shall be permitted for systems with a ceiling supply of warm air, provided that supply air temperature is less than 15°F above space temperature and provided that the 150-foot- per-minute supply air jet reaches to within 41/2 feet of floor level.
The zone outdoor airflow rate (Voz), shall be determined in accordance with Equation 4-2.

The outdoor air required to be supplied by each ventilation system shall be determined in accordance with Sections 403.3.1.1.2.1 through 403.3.1.1.2.3 as a function of system type and zone outdoor airflow rates.
Where one air handler supplies a mixture of outdoor air and recirculated return air to only one zone, the system outdoor air intake flow rate (Vot) shall be determined in accordance with Equation 4-3.

Where one air handler supplies only outdoor air to one or more zones, the system outdoor air intake flow rate (Vot) shall be determined using Equation 4-4.

Where one air handler supplies a mixture of outdoor air and recirculated return air to more than one zone, the system outdoor air intake flow rate (Vot) shall be determined in accordance with Sections 403.3.1.1.2.3.1 through 403.3.1.1.2.3.4.
The primary outdoor air fraction (Zp) shall be determined for each zone in accordance with Equation 4-5.



where:

Vpz=Primary airflow: The airflow rate supplied to the zone from the airhandling unit at which the outdoor air intake is located. It includes outdoor intake air and recirculated air from that air-handling unit but does not include air transferred or air recirculated to the zone by other means. For design purposes, Vpzshall be the zone design primary airflow rate, except for zones with variable air volume supply and Vpz shall be the lowest expected primary airflow rate to the zone when it is fully occupied.
The system ventilation efficiency (Ev) shall be determined using Table 403.3.1.1.2.3.2 or Appendix A of ASHRAE 62.1.

TABLE 403.3.1.1.2.3.2 SYSTEM VENTILATION EFFICIENCYa,b

Max (Zp) Ev
≤ 0.15 1
≤ 0.25 0.9
≤ 0.35 0.8
≤ 0.45 0.7
≤ 0.55 0.6
≤ 0.65 0.5
≤ 0.75 0.4
> 0.75 0.3

a. Max (Zp ) is the largest value of Zp calculated using Equation 4-5 among all the zones served by the system.
b. Interpolating between table values shall be permitted.
The uncorrected outdoor air intake flow rate (Vou) shall be determined in accordance with Equation 4-6.



where:

D=Occupant diversity: the ratio of the system population to the sum of the zone populations, determined in accordance with Equation 4-7.



where:

Ps=System population: The total number of occupants in the area served by the system. For design purposes, Ps shall be the maximum number of occupants expected to be concurrently in all zones served by the system.
The outdoor air intake flow rate (Vot) shall be determined in accordance with Equation 4-8.

Exhaust airflow rate shall be provided in accordance with the requirements of Table 403.3.1.1. Outdoor air introduced into a space by an exhaust system shall be considered as contributing to the outdoor airflow required by Table 403.3.1.1.
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.
Variable air volume air distribution systems, other than those designed to supply only 100-percent outdoor air, shall be provided with controls to regulate the flow of outdoor air. Such control system shall be designed to maintain the flow rate of outdoor air at a rate of not less than that required by Section 403.3 over the entire range of supply air operating rates.
The ventilation air distribution system shall be provided with means to adjust the system to achieve not less than the minimum ventilation airflow rate as required by Sections 403.3 and 403.3.1.2. Ventilation systems shall be balanced by an approved method. Such balancing shall verify that the ventilation system is capable of supplying and exhausting the airflow rates required by Sections 403.3 and 403.3.1.2.
The design of local exhaust systems and ventilation systems for outdoor air in Group R-2, R-3 and R-4 occupancies three stories and less in height above grade plane shall comply with Sections 403.3.2.1 through 403.3.2.3.
UpCodes note: The Washington State Mechanical Code amendments state that "This section is not adopted. See Section 403.8".
An outdoor air ventilation system consisting of a mechanical exhaust system, supply system or combination thereof shall be installed for each dwelling unit. Local exhaust or supply systems, including outdoor air ducts connected to the return side of an air handler, are permitted to serve as such a system. The outdoor air ventilation system shall be designed to provide the required rate of outdoor air continuously during the period that the building is occupied. The minimum continuous outdoor airflow rate shall be determined in accordance with Equation 4-9.

QOA = 0.01 Afloor + 7.5(Nbr + 1) (Equation 4-9)


where:

QOA = outdoor airflow rate, cfm
Afloor = floor area, ft2
Nbr = number of bedrooms; not to be less than one


Exception: The outdoor air ventilation system is not required to operate continuously where the system has controls that enable operation for not less than 1 hour of each 4-hour period. The average outdoor air flow rate over the 4-hour period shall be not less than that prescribed by Equation 4-9.
Corridors and other common areas within the conditioned space shall be provided with outdoor air at a rate of not less than 0.06 cfm per square foot of floor area.

403.3.2.3 Local Exhaust

STATE AMENDMENT
Local exhaust systems shall be provided in kitchens, bathrooms and toilet rooms and shall have the capacity to exhaust the minimum airflow rate determined in accordance with Table 403.3.2.3.

TABLE 403.3.2.3 MINIMUM REQUIRED LOCAL EXHAUST RATES FOR GROUP R-2, R-3, AND R-4 OCCUPANCIES

AREA TO BE EXHAUSTED EXHAUST RATE CAPACITY
Kitchens 100 cfm intermittent or
25 cfm continuous
Bathrooms and toilet rooms 50 cfm intermittent or
20 cfm continuous

For SI: 1 cubic foot per minute = 0.0004719 m3/s.
UpCodes note: The Washington State Mechanical Code amendments notes that "There are no Sections 403.4, 403.5, 403.6 or 403.7. The numbering from the 2012 edition was retained for Section 403.8 for ease of use."
Each dwelling unit or sleeping unit shall be equipped with local exhaust and whole house ventilation systems and shall comply with Sections 403.8.1 through 403.8.11. All occupied spaces, including public corridors, other than the Group R dwelling and sleeping unit, that support the Group R occupancy shall meet the ventilation requirements of Section 402 or the applicable rates from Table 403.3.1.1.
Ventilation systems shall be designed and installed to satisfy the ventilation requirements of Table 403.3.1.1 or Table 403.8.1. Breathing zone ventilation rates from Table 403.3.1.1 shall be calculated per Section 403.3.1.1 and corrected per zone air distribution effectiveness requirements per Section 403.3.1.2.

TABLE 403.8.1
VENTILATION RATES FOR ALL GROUP R
PRIVATE DWELLINGS, SINGLE AND MULTIPLE
(Continuously Operating Systems)


Floor Area
(ft2)
Bedroomsa
0-1 2-3 4-5 6-7 >7
<500 30 40 45 55 60
500 - 1000 45 55 60 70 75
1001 - 1500 60 70 75 85 90
1501 - 2000 75 85 90 100 105
2001 - 2500 90 100 105 115 120
2501 - 3000 105 115 120 130 135
3001 - 3500 120 130 135 145 150
>3500 135 145 150 160 165
a. Ventilation rates in table are minimum outdoor airflow rates measured in cfm.

  1. Location of controls. Controls for all ventilation systems shall be readily accessible by the occupant.
  2. Instructions. Operating instructions for whole house ventilation systems shall be provided to the occupant by the installer of the system.
  3. Local ventilation systems. Local ventilation systems shall be controlled by manual switches, dehumidistats, timers, or other approved means.
  4. Continuous whole house ventilation systems. Continuous whole house ventilation systems shall operate continuously and be equipped with an override control. A “fan on”switch shall be permitted as an override control. Controls shall be capable of operating the ventilation system without energizing other energy-consuming appliances. A clearly visible label shall be affixed to the controls that reads "Whole House Ventilation (see operating instructions)."
  5. Intermittent whole house ventilation systems. Intermittent whole house ventilation systems shall comply with the following:

    1. They shall be capable of operating intermittently and continuously.
    2. They shall have controls capable of operating the exhaust fans, forced-air system fans, or supply fans without energizing other energy-consuming appliances.
    3. The ventilation rate shall be adjusted according to the exception in Section 403.8.5.1.
    4. The system shall be designed so that it can operate automatically based on the type of control timer installed.
    5. The intermittent mechanical ventilation system shall operate at least one hour out of every four.
    6. The system shall have a manual control and automatic control, such as a 24-hour clock timer.
    7. At the time of final inspection, the automatic control shall be set to operate the whole house fan according to the schedule used to calculate the whole house fan sizing.
    8. A label shall be affixed to the control that reads "Whole House Ventilation (see operating instructions)."
  6. Exception: Engineered central ventilation systems serving dwelling units or sleeping units are not required to have individual controls for each dwelling unit or sleeping unit when designed for continuous operation and approved by the code official.
Outdoor air intakes shall be classified as either operable openings or mechanical air intakes and shall be located per the following criteria. The intake locations for operable openings and mechanical air intakes shall comply with the following:

  1. Openings for mechanical air intakes shall comply with Section 401.4. Operable openings shall comply with Section 401.4 items 2 and 4 only.
  2. Intake openings shall not be located closer than 10 feet from an appliance vent outlet unless such vent outlet is 3 feet above the outdoor air inlet. The vent shall be permitted to be closer if specifically allowed by Chapter 8 or by the International Fuel Gas Code.
  3. Intake openings shall be located where they will not pick up objectionable odors, fumes, or flammable vapors.
  4. Intake openings shall be located where they will not take air from a hazardous or unsanitary location.
  5. Intake openings shall be located where they will not take air from a room or space having a fuel-burning appliance.
  6. Intake openings shall not be located closer than 10 feet from a vent opening of a plumbing drainage system unless the vent opening is at least 3 feet above the air inlet.
  7. Intake openings shall not be located where they will take air from an attic, crawl space, or garage.
  8. Intake openings shall not be located on asphalt roofs unless it is shown that no other locationis permissible. In such cased, the inlet opening shall be located a minimum of 2 feet from the nearest surface of the asphalt roofing, measured from the intake opening.
Local exhaust ventilation systems shall exhaust at least the volume of air required for exhaust in Table 403.3.1.1. Exhaust shall be provided in each kitchen, bathroom, water closet, laundry area, indoor swimming pool, spa, and other room where water vapor or cooking odor is produced.
Exhaust systems shall be designed and installed to meet all of the criteria below:

  1. Local exhaust shall be discharged outdoors.
  2. Exhaust outlets shall comply with Section 501.3.
  3. Pressure equalization shall comply with Section 501.4.
  4. Exhaust ducts in systems which are designed to operate intermittently shall be equipped with back-draft dampers.
  5. All exhaust ducts in unconditioned spaces shall be insulated to a minimum of R-4.
  6. Terminal outlet elements shall have at least the equivalent net free area of the ductwork.
  7. Terminal outlet elements shall be screened or otherwise protected as required by Section 501.3.2.
  8. Exhaust fans in separate dwelling units or sleeping units shall not share common exhaust ducts unless the system is engineered for this operation.
  9. Where permitted by Chapter 5, multiple local exhaust ducts may be combined. If more than one of the exhaust fans in a dwelling unit or sleeping unit shares a common exhaust duct then each exhaust fan shall be equipped with a back-draft damper to prevent the recirculation of exhaust air from one room to another room via the exhaust ducting system.
Exhaust fan construction and sizing shall meet the following criteria.

  1. Exhaust fans shall be tested and rated in accordance with the airflow and sound rating procedures of the Home Ventilating Institute (HVI 915, HVI Loudness Testing and Rating Procedure, HVI 916, HVI Airflow Test Procedure, and HVI 920, HVI Product Performance Certification Procedure).

    Exception: Where a range hood or down draft exhaust fan is used for local exhaust for a kitchen, the device is not required to be rated per these standards.
  2. Installation of the system or equipment shall be carried out in accordance with manufacturers' installation instructions.
  3. Fan airflow rating and duct system shall be designed and installed to deliver at least the exhaust airflow required by Table 403.3.1.1. 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.

    Exceptions:
    1. 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 403.8.4.2.
    2. Where a range hood or down draft exhaust fan is used to satisfy the local ventilation requirements for kitchens, the range hood or down draft exhaust shall not be less than 100 cfm at 0.10 in. w.g.
TABLE 403.8.4.2
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.
Each dwelling unit or sleeping unit shall be equipped with one of the following four types of mechanical whole house ventilation systems: A system using exhaust fans (see Section 403.8.6); a system integrated with forced-air systems (see Section 403.8.7); a system using supply fans (see Section 403.8.8); or a heat or energy recovery ventilation system (see Section 403.8.9). The whole house exhaust system is permitted to be one of the local exhaust systems required by Section 403.8.4 as long as the requirements of this section, in addition to the requirement of Section 403.8.5, are met.

Exception: Additions, alterations, renovations or repairs to a mechanical system that is part of a building addition with less than 500 square feet of conditioned floor are are exempt from the requirements for whole house ventilation systems, Section 403.8.5.

403.8.5.1 Outdoor Air

STATE AMENDMENT
Outdoor air shall be distributed to each habitable space.

Where outdoor air supply intakes are separated from exhaust vents by doors, means shall be provided to ensure airflow to all separated habitable spaces by installing distribution ducts, installed grilles, transoms, doors undercut to a minimum of 1/2-inch above the surface of the finish floor covering, or other similar means where permitted by the International Building Code.

The mechanical system shall operate continuously to supply at least the volume of outdoor air required in Table 403.3.1.1 or Table 403.8.1.

Exception: Intermittently operating ventilation systems: The whole house mechanical ventilation system is permitted to operate intermittently where the system has controls that enable operation for not less than 25 percent of each 4-hour segment and the ventilation rate prescribed in Table 403.3.1.1 or Table 403.8.1 is multiplied by the factor determined in accordance with Table 403.8.5.1.


TABLE 403.8.5.1
INTERMITTENT WHOLE HOUSE MECHANICAL
VENTILATION RATE FACTORSa,b

Run-Time
% in Each
4-hour
Segment
25% 33% 50% 66% 75% 100%
Factora 4 3 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.
Whole house ventilation systems integrated with a forced-air system, systems using supply fans and systems using a heat or energy recovery ventilation system shall comply with the following.

  1. Outdoor air louvers shall be adequately sized for the required airflow and shall comply with Section 401.5. Outdoor air intake locations shall comply with mechanical air intakes requirements of Section 403.8.3.
  2. Outdoor air ducts for dedicated or central supply systems and exhaust ducts for heat or energy recovery systems shall be provided with a means for balancing the system to the required airflow via balance dampers or other devices.
  3. Outdoor air ducts, for dedicated or central systems shall be provided with motorized dampers.

    Exceptions:
    1. Outdoor air ducts at heat or energy ventilation systems are not required to have motorized dampers.
    2. Outdoor air ducts at continuous ventilation systems are not required to have motorized dampers.
  4. Oudoor air ducts in the conditioned space shall be insulated to a minimum of R-4. In heat or energy recovery ventilation systems, ducts upstream of the heat exchanger shall also be insulated to at least R-4.
  5. All outdoor air ducts shall be designed and installed to deliver at least the outdoor airflow required by Section 403.8.5.1. 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.

    Exception: The outdoor air duct for supply fan systems and heat or energy recovery systems may be prescriptively sized per Table 403.8.5.2 for dedicated outdoor air ducts upstream of the supply fan. Supply fans shall have the capacity to provide the amount of outdoor air required by Section 403.8.5.1 at 0.40 in. w.g. as per HVI 916 (April 1995). When prescriptively sized the system shall be tested and balanced using a flow hood, flow-grid, or other airflow measurement device.
  6. Whole house ventilation controls for intermittent operation shall allowconcurrent operation of the forced-air fan and the associated outdoor air motorized damper.
  7. Whole house ventilation controls for continuous operation shall be provided at the forced-air fan.

    Exception: Engineered central ventilation systems serving dwelling units or sleeping units are not required to have individual controls for each dwelling unit or sleeping unit when designed for continuous operation and approved by the code official.
TABLE 403.8.5.2
PRESCRIPTIVE SUPPLY FAN DUCT SIZING

Supply Fan Tested CFM at 0.40” w.g.
Specified
Volume from
Table 403.8.1
Minimum
Smooth Duct
Diameter
Minimum
Flexible Duct
Diameter
50-90 cfm 4 inch 5 inch
90-150 cfm 5 inch 6 inch
150-120 cfm 6 inch 7 inch
250-400 cfm 7 inch 8 inch
This section establishes minimum requirements for mechanical whole house ventilation systems using exhaust fans.

403.8.6.1 Outdoor Air

STATE AMENDMENT
Exhaust fan only ventilation systems shall provide outdoor air to each occupiable space through one of the following methods:

  1. Outdoor air may be drawn through air inlets installed in exterior walls or windows. The air inlets shall comply with all of the following:

    1. Inlets shall have controllable, secure openings and shall be designed to not compromise the thermal properties of the building envelope.
    2. Inlets shall be accessible to occupants, including compliance with Section 1109.13 of the International Building Code for designated accessible units, Type A units and Type B units.
    3. Inlets shall be screened or otherwise protected from entry by insects, leaves, or other material.
    4. Inlets shall provide not less than 4 square inches of net free area of opening for each 10 cfm of outdoor air required in Table 403.3.1.1 or Table 403.8.1.
    5. Any inlet or combination of inlets which provide 10 cfm at 10 Pascals as determined by the Home Ventilation Institute Air Flow Test Standard (HVI 901 (November 1996)) are deemed equivalent to 4 square inches of net free area.
    6. Each occupiable space shall have a minimum of one air inlet that has a minimum of 4 square inches of net free area.
  2. Outdoor air may be drawn in through operable openings to the outdoors. Each habitable space shall be provided with operable openings with an openable area of not less than 4 square inches of net free area of opening for each 10 cfm of outdoor air required by Table 403.3.1.1 or Table 403.8.1. Doors exiting to a corridor, court or public way shall not be used to provide outdoor air. The operable openings shall comply with the following:

    1. Openings shall be controllable, securable, and shall be designed to not compromise the thermal properties of the building envelope.
    2. Openings shall be accessible to occupants, including compliance with Section 1109.13 of the International Building Code for designated accessible units, Type A units and Type B units.
    3. Openings shall be screened or otherwise protected from entry by leaves or other material.
  3. For interior adjoining spaces without outdoor air openings, one of the following two options shall be used to ventilate the interior adjoining space:

    1. Provide a whole house transfer fan at the interior adjoining space sized to provide a minimum of the ventilation rate required per Section 403.8.5.1. The transfer fan shall circulate air between the interior room or space and the adjacent habitable space. The transfer fan may operate continuously or intermittently using controls per Section 403.8.2.
    2. Provide a permanent opening to the interior adjoining space. Opening shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior adjoining space, but not less than 25 square feet
All outside air intake opening types described in Section 403.8.6.1 shall be classified operable openings and shall not be classified as mechanical air intakes. The intake locations shall comply with Section 403.8.3.
Whole house exhaust system shall be designed and installed to meet all of the applicable criteria below:

  1. Whole house ventilation exhaust shall be discharged outdoors.
  2. Exhaust outlets shall comply with Section 501.2.
  3. Exhaust ducts in systems which are designed to operate intermittently shall be equipped with back-draft dampers.
  4. All exhaust ducts in unconditioned spaces shall be insulated to a minimum of R-4.5. Terminal outlet elements shall have at least the equivalent net free area of the ductwork.
  5. Terminal outlet elements shall be screened or otherwise protected as required by Section 501.2.2.
  6. One of the required local exhaust fans for the laundry room or bathroom may be designated as the whole house exhaust fan.
  7. Exhaust fans in separate dwelling units or sleeping units shall not share common exhaust ducts unless the system is engineered for this operation.
  8. Where permitted by Chapter 5 whole house exhaust ducts may be combined with other local exhaust ducts. If more than one of the exhaust fans in a dwelling unit or sleeping unit shares a common exhaust duct then each exhaust fan shall be equipped with a back-draft damper to prevent the recirculation of exhaust air from one room to another room via the exhaust ducting system.
Exhaust fan construction and sizing shall meet the following criteria.

  1. Exhaust and transfer fans shall be tested and rated in accordance with the airflow and sound rating procedures of the Home Ventilating Institute (HVI 915, HVI Loudness Testing and Rating Procedure, HVI 916, HVI Airflow Test Procedure, and HVI 920, HVI Product Performance Certification Procedure).
  2. Installation of system or equipment shall be carried out in accordance with manufacturers' design requirements and installation instructions.
  3. Fan airflow rating and duct system shall be designed and installed to deliver at least the outdoor airflow required by Table 403.3.1.1 or Table 403.8.1. 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.

    Exception: An airflow rating at a pressure of 0.25 in. w.g. may be used, provided the duct sizing meets the prescriptive requirements of Table 403.8.5.2.

403.8.6.5 Fan Noise

STATE AMENDMENT
Whole house exhaust and transfer fans located 4 feet or less from the interior grille shall have a sone rating of 1.0 or less measured at 0.10 inches water gauge. Manufacturer's noise ratings shall be determined as per HVI 915. Remotely mounted fans shall be acoustically isolated from the structural elements of the building and from attached ductwork using insulated flexible duct or other approved material.
This section establishes minimum requirements for mechanical whole house ventilation systems using forced-air system fans.

403.8.7.1 Outdoor Air

STATE AMENDMENT
Forced-air system fan ventilation systems shall provide outdoor air through one of the following methods:

  1. A dedicated outdoor air louver and outdoor air duct for each dwelling unit or sleeping unit shall supply outdoor air to the return side of the forced-air system fan; or
  2. A central outdoor air delivery system that supplies multiple dwelling units or sleeping units shall supply outdoor air to the return side of the forced air system fan.
  3. For interior adjoining spaces without outdoor air openings, one of the following two options shall be used to ventilate the interior adjoining space:

    1. Provide a whole house transfer fan at the interior adjoining space sized to provide a minimum of the ventilation rate required per Section 403.8.5.1. The transfer fan shall circulate air between the interior room or space and the adjacent habitable space. The transfer fan may operate continuously or intermittently using controls per Section 403.8.2.
    2. Provide a permanent opening to the interior adjoining space. Opening shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior adjoining space, but not less than 25 square feet.
Where outdoor air is provided to each habitable dwelling unit or sleeping unit by a forced-air system, the outdoor air duct shall be connected to the return air stream at a point within 4 feet upstream of the forced-air unit. It shall not be connected directly to the forced-air unit cabinet in order to prevent thermal shock to the heat exchanger. At a minimum, filtration of the outdoor air shall be provided at the forced- air unit. The filter shall be accessible for regular maintenance and replacement. The filter shall have a Minimum Efficiency Rating Value (MERV) of at least 6.

Each habitable space in the dwelling or sleeping unit shall be served by a forced-air system with outdoor air connection.
This section establishes minimum requirements for mechanical whole house ventilation systems using supply fan systems.

403.8.8.1 Outdoor Air

STATE AMENDMENT
Supply fan ventilation systems shall provide outdoor air through one of the following methods:

  1. A dedicated outdoor air louver and outdoor air duct for each dwelling unit or sleeping unit shall supply outdoor air to a supply fan; or
  2. A central outdoor air supply fan system shall distribute unconditioned or conditioned air to multiple dwelling units or sleeping units.
  3. For interior adjoining spaces without outdoor air openings, one of the following two options shall be used to ventilate the interior adjoining space:

    1. Provide a whole house transfer fan at the interior adjoining space sized to provide a minimum of the ventilation rate required per Section 403.8.5.1. The transfer fan shall circulate air between the interior room or space and the adjacent habitable space. The transfer fan may operate continuously or intermittently using controls per Section 403.8.2.
    2. Provide a permanent opening to the interior adjoining space. Opening shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior adjoining space, but not less than 25 square feet.
Where outdoor air is provided to each habitable dwelling unit or sleeping unit by supply fan systems the outdoor air shall be filtered.

The system filter may be located at the intake device or inline with the fan. The filter shall be accessible for regular maintenance and replacement. The filter shall have a Minimum Efficiency Rating Value (MERV) of at least 6.
This section establishes minimum requirements for mechanical whole house ventilation systems using heat recovery or energy recovery ventilation systems.

403.8.9.1 Outdoor Air

STATE AMENDMENT
Heat recovery or energy recovery ventilation systems shall provide outdoor air through one of the following methods:

  1. A dedicated outdoor air louver and outdoor air duct for each dwelling unit or sleeping unit shall supply outdoor air to the heat recovery or energy recovery ventilator; or
  2. A central outdoor air heat recovery or energy recovery unit shall distribute conditioned air to multiple dwelling units or sleeping units.
  3. For interior adjoining spaces without outdoor air openings, one of the following two options shall be used to ventilate the interior adjoining space:

    1. Provide a whole house transfer fan at the interior adjoining space sized to provide a minimum of the ventilation rate required per Section 403.8.5.1. The transfer fan shall circulate air between the interior room or space and the adjacent habitable space. The transfer fan may operate continuously or intermittently using controls per Section 403.8.2.
    2. Provide a permanent opening to the interior adjoining space. Opening shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior adjoining space, but not less than 25 square feet.
Where outdoor air is provided to each habitable dwelling unit or sleeping unit by heat recovery or energy recovery ventilator the outdoor air shall be filtered. The filter shall be located on the upstream side of the heat exchanger in both the intake and exhaust airstreams with a Minimum Efficiency Rating Value (MERV) of at least 6. The system filter may be located at the intake device or inline with the fan. The filter shall be accessible for regular maintenance and replacement.

Each habitable space in the dwelling or sleeping unit shall be served by a heat recovery ventilator system with outdoor air connection.
In lieu of complying with Sections 403.8.4 or 403.8.5 compliance with the section shall be demonstrated through engineering calculations by an engineer licensed to practice in the state of Washington or by performance testing. Documentation of calculations or performance test results shall be submitted to and approved by the building official. Performance testing shall be conducted in accordance with approved test methods.

403.8.11 Alternate Systems

STATE AMENDMENT
When approved by the code official, systems designed in accordance with ASHRAE Standard 62.2 shall be permitted.
Where mechanical ventilation systems for enclosed parking garages operate intermittently, such operation shall be automatic by means of carbon monoxide detectors applied in conjunction with nitrogen dioxide detectors. Such detectors shall be installed in accordance with their manufacturers' recommendations.
Automatic operation of the system shall not reduce the ventilation airflow rate below 0.05 cfm per square foot (0.00025 m3/s • m2) of the floor area and the system shall be capable of producing a ventilation airflow rate of 0.75 cfm per square foot (0.0038 m3/s • m2) of floor area.
Connecting offices, waiting rooms, ticket booths and similar uses that are accessory to a public garage shall be maintained at a positive pressure and shall be provided with ventilation in accordance with Section 403.3.1.
In 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. Exhaust extension duct over 10 feet in length shall mechanically exhaust at least 300 cfm. Connecting offices and waiting rooms shall be supplied with conditioned air under positive pressure.
Mechanical ventilation systems shall be provided with manual or automatic controls that will operate such systems whenever the spaces are occupied. Air-conditioning systems that supply required ventilation air shall be provided with controls designed to automatically maintain the required outdoor air supply rate during occupancy.
Uninhabited spaces, such as crawl spaces and attics, shall be provided with natural ventilation openings as required by the International Building Code or shall be provided with a mechanical exhaust and supply air system. The mechanical exhaust rate shall be not less than 0.02 cfm per square foot (0.00001 m3/s • m2) of horizontal area and shall be automatically controlled to operate when the relative humidity in the space served exceeds 60 percent.

407.1 General

STATE AMENDMENT
Mechanical ventilation for ambulatory care facilities and Group I-2 occupancies shall be designed and installed in accordance with this code and ASHRAE 170.
Mechanical ventilation for health care facilities licensed by Washington state shall be designed and installed in accordance with this code and the following provisions of the Washington Administrative Code (WAC):
  1. Mechanical ventilation in ambulatory care facilities shall comply with chapter 246-330 WAC.
  2. Mechanical ventilation for acute care hospitals shall comply with chapter 246-320 WAC.
  3. Mechanical ventilation for nursing homes shall comply with chapter 388-97 WAC. Mechanical ventilation for unlicensed ambulatory care facilities shall be designed and installed in accordance with this code and ASHRAE 170.
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