About this chapter: Chapter 4 intends to provide an indoor atmosphere that protects the health and well-being of building occupants. Both mechanical and natural ventilation are addressed. Mechanical ventilation provides what is considered to be acceptable indoor air quality. Mechanical ventilation minimizes adverse health effects and provides an atmosphere that generally is not objectionable to occupants.
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.
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.
Ventilation shall be provided during the periods that the room or space is occupied.
Air intake openings shall comply with all of the following:
- Intake openings shall be located not less than 10 feet (3048 mm) from lot lines or buildings on the same lot.
- 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.
- 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.
- 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.
OPENING SIZES IN LOUVERS, GRILLES AND SCREENS PROTECTING AIR INTAKE OPENINGS
|OUTDOOR OPENING TYPE||MINIMUM AND MAXIMUM OPENING|
SIZES IN LOUVERS, GRILLES AND SCREENSa
|Intake openings in|
|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.
- For rectangular openings, the table requirements apply to the shortest side. For round openings, the table requirements apply to the diameter. For square openings, the table requirements apply to any side.
Stationary local sources producing airborne 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.
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 sun-room 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 outdoor 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.
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.
The minimum outdoor airflow rate shall be determined in accordance with Section 403.3.
Exception: 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.
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:
- Ventilation air shall not be recirculated from one dwelling to another or to dissimilar occupancies.
- 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 of the resulting supply airstream consists of air recirculated from these spaces.
- 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.
- 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 air-stream 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. Other buildings intended to be occupied shall be provided with outdoor air and local exhaust in accordance with Section 403.3.1.
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 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.
MINIMUM VENTILATION RATES
|OCCUPANCY CLASSIFICATION||OCCUPANT DENSITY|
#/1000 FT2 a
AIRFLOW RATE IN
AIRFLOW RATE IN
Ra CFM/FT2 a
|without plumbing fixtures||25||5||0.12||—|
|with plumbing fixturesg||25||5||0.12||1.0|
(see "Food and beverage service")
|Dry cleaners, laundries|
|Coin-operated dry cleaner||20||15||—||—|
|Commercial dry cleaner||30||30||—||—|
|Storage, pick up||30||7.5||0.12||—|
|Classrooms (ages 5-8)||25||10||0.12||—|
|Classrooms (age 9 plus)||35||10||0.12||—|
|Corridors (see "Public spaces")||—||—||—||—|
|Day care (through age 4)||25||10||0.18||—|
|Lecture hall (fixed seats)||150||7.5||0.06||—|
|Sports locker roomsg||—||—||—||0.5|
|Food and beverage service|
|Bars, cocktail lounges||100||7.5||0.18||—|
|Cafeteria, fast food||100||7.5||0.18||—|
|Hotels, motels, resorts and dormitories|
|Dormitory sleeping areas||20||5||0.06||—|
|Main entry lobbies||10||5||0.06||—|
|Private dwellings, single and multiple|
|Garages, common for multiple unitsb||—||—||—||0.75|
|Living areasc||Based on number|
of bedrooms. Firstbedroom, 2; each
additional bedroom, 1
|0.35 ACH but not less|
than 15 cfm/person
|Toilet rooms and bathroomsg||—||—||—||20/50f|
|Places of religious worship||120||5||0.06||—|
|Shower room (per shower head)g||—||—||—||50/20f|
|Toilet rooms — publicg||—||—||—||50/70e|
|Retail stores, sales floors and|
|Mall common areas||40||7.5||0.06||—|
|Shipping and receiving||2||10||0.12||—|
|Warehouses (see "Storage")||—||10||0.06||—|
|Automotive motor-fuel dispensing stationsb||—||—||—||1.5|
|Nail salons b, h||25||20||0.12||0.6|
|Pet shops (animal areas)b||10||7.5||0.18||0.9|
|Sports and amusement|
|Bowling alleys (seating areas)||40||10||0.12||—|
|Gym, stadium, arena (play area)||7||20||0.18||—|
|Health club/aerobics room||40||20||0.06||—|
|Health club/weight room||10||20||0.06||—|
|Ice arenas without combustion engines||—||—||0.30||0.5|
|Swimming pools (pool and deck area)||—||—||0.48||—|
|Repair garages, enclosed parking garagesb,d||—||—||—||0.75|
|Auditoriums (see "Education")||—||—||—||—|
|Bank vaults/safe deposit||5||5||0.06||—|
|Computer (without printing)||4||5||0.06||—|
|Copy, printing rooms||4||5||0.06||0.5|
|Pharmacy (prep. area)||10||5||0.18||—|
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.
- Based on net occupiable floor area.
- 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).
- Spaces unheated or maintained below 50°F are not covered by these requirements unless the occupancy is continuous.
- Ventilation systems in enclosed parking garages shall comply with Section 404.
- 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.
- 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.
- 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).
- For nail salons, each manicure and pedicure station 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.
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.
The zone air distribution effectiveness (Ez) shall be determined using 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 or return
|Makeup air drawn in near to the exhaust or return|
For SI: 1 foot = 304.8 mm, 1 foot per minute = 0.00506 m/s, °C = [(°F) — 32]/1.8.
- "Cool air" is air cooler than space temperature.
- "Warm air" is air warmer than space temperature.
- "Ceiling" includes any point above the breathing zone.
- "Floor" includes any point below the breathing zone.
- 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.
- 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 primary outdoor air fraction (Zp) shall be determined for each zone in accordance with Equation 4-5.
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, Vpz shall 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.
The uncorrected outdoor air intake flow rate (Vou) shall be determined in accordance with Equation 4-6.
D = Occupant diversity: the ratio of the system population to the sum of the zone populations, determined in accordance with Equation 4-7.
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.
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.
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 = outdoor airflow rate, cfm
Afloor = floor area, ft2
Nbr = number of bedrooms; not to be less than one
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.
Mechanical ventilation systems for enclosed parking garages shall operate continuously or shall be automatically operated by means of carbon monoxide detectors applied in conjunction with nitrogen dioxide detectors. Such detectors shall be listed in accordance with UL 2075 and installed in accordance with their listing and the manufacturers' instructions. Automatic operation shall cycle the ventilation system between the following two modes of operation:
- Full-on at an airflow rate of not less than 0.75 cfm per square foot [0.0038 m3/(s • m2)] of the floor area served.
- Standby at an airflow rate of not less than 0.05 cfm per square foot [0.00025 m3/(s • m2)] of the floor area served.
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.