Chapter 4 Ventilation
Section 401 General
401.1 Scope.
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.
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 three air changes per hour when tested with a blower door at a pressure of 0.2-inch water column (50 Pa) in accordance with the Georgia State Minimum Standard Energy 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.
401.3 When required.
Ventilation shall be provided during the periods that the room or space is occupied.
401.4 Intake opening location.
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. Separation is not required between intake air openings and living space exhaust air openings of an individual dwelling unit or sleeping unit where a factory-built intake/exhaust combination termination fitting is used to separate the air streams in accordance with the fan manufacturer’s instructions.
- 4.
401.5 Intake opening protection.
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.
OUTDOOR OPENING TYPE | MINIMUM AND MAXIMUM OPENING SIZES IN LOUVERS, GRILLES AND SCREENSa |
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.
- a.
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.
401.6 Contaminant sources.
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.
401.7 Alternative ventilation procedures.
As an alternative to Chapter 4, the following shall be permitted:
- 1.
- 2.
Section 402 Natural Ventilation
[BG] 402.1 Natural ventilation.
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.
[BG] 402.2 Ventilation area required.
The minimum openable area to the outdoors shall be 4 percent of the floor area being ventilated.
[BG] 402.3 Adjoining spaces.
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.
[BG] 402.4 Openings below grade.
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.
Section 403 Mechanical Ventilation
403.1 Ventilation system.
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 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.
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.
403.2.1 Recirculation of air.
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 of the resulting supply airstream consists of air recirculated from these spaces. The design and installation of dehumidification systems shall comply with ANSI/ACCA 10 Manual SPS.
- 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.
403.2.2 Transfer air.
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.
403.3 Outdoor air and local exhaust airflow rates.
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.
403.3.1 Other buildings intended to be occupied.
The design of local exhaust systems and ventilation systems for outdoor air for occupancies other than Groups R-2, R-3 and R-4 shall comply with Sections 403.3.1.1 through 403.3.1.4.
403.3.1.1 Outdoor airflow rate.
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.
OCCUPANCY CLASSIFICATION | OCCUPANT DENSITY #/1000 FT2 a | PEOPLE OUTDOOR AIRFLOW RATE IN BREATHING ZONE, Rp CFM/PERSON | AREA OUTDOOR AIRFLOW RATE IN BREATHING ZONE, RaCFM/FT2 a | EXHAUST AIRFLOW RATE CFM/FT2 a |
Animal facilities | ||||
Animal exam room (veterinary office) | 20 | 10 | 0.12 | — |
Animal imaging (MR/CT/PET) | 20 | 10 | 0.18 | 0.9 |
Animal operating rooms | 20 | 10 | 0.18 | 3.00 |
Animal postoperative recovery room | 20 | 10 | 0.18 | 1.50 |
Animal preparation rooms | 20 | 10 | 0.18 | 1.50 |
Animal procedure room | 20 | 10 | 0.18 | 2.25 |
Animal surgery scrub | 20 | 10 | 0.18 | 1.50 |
Large-animal holding room | 20 | 10 | 0.18 | 2.25 |
Necropsy | 20 | 10 | 0.18 | 2.25 |
Small-animal cage room (static cages) | 20 | 10 | 0.18 | 2.25 |
Small-animal cage room (ventilated cages) | 20 | 10 | 0.18 | 1.50 |
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 | — | — | — | — |
Guard stations | 15 | 5 | 0.06 | — |
Dry cleaners, laundries | ||||
Coin-operated dry cleaner | 20 | 15 | — | — |
Coin-operated laundries | 20 | 7.5 | 0.12 | — |
Commercial dry cleaner | 30 | 30 | — | — |
Commercial laundry | 10 | 5 | 0.12 | — |
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 | — |
Break rooms | 25 | 5 | 0.06 | — |
Cafeteria, fast food | 100 | 7.5 | 0.18 | — |
Coffee stations | 20 | 5 | 0.06 | — |
Corridors | — | — | 0.06 | — |
Dining rooms | 70 | 7.5 | 0.18 | — |
Kitchens (cooking)b | 20 | 7.5 | 0.12 | 0.7 |
Occupiable storage rooms for liquids or gels | 2 | 5 | 0.12 | — |
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 | — |
Laundry rooms, central | 10 | 5 | 0.12 | — |
Laundry rooms within dwelling units | 10 | 5 | 0.12 | — |
Lobbies/prefunction | 30 | 7.5 | 0.06 | — |
Multipurpose assembly | 120 | 5 | 0.06 | — |
Offices | ||||
Break rooms | 50 | 5 | 0.12 | — |
Conference rooms | 50 | 5 | 0.06 | — |
Main entry lobbies | 10 | 5 | 0.06 | — |
Occupiable storage rooms for dry materials | 2 | 5 | 0.06 | — |
Office spaces | 5 | 5 | 0.06 | — |
Reception areas | 30 | 5 | 0.06 | — |
Telephone/data entry | 60 | 5 | 0.06 | — |
Outpatient healthcare facilitiesi, j | ||||
Birthing room | 15 | 10 | 0.18 | — |
Class 1 imaging room | 5 | 5 | 0.12 | — |
Dental operatoryk | 20 | 10 | 0.18 | — |
General examination room | 20 | 7.5 | 0.12 | — |
Other dental treatment areas | 5 | 5 | 0.06 | — |
Physical therapy exercise area | 7 | 20 | 0.18 | — |
Physical therapy individual room | 20 | 10 | 0.06 | — |
Physical therapeutic pool area | — | — | 0.48 | — |
Prosthetics and orthotics room | 20 | 10 | 0.18 | — |
Psychiatric consultation room | 20 | 5 | 0.06 | — |
Psychiatric examination room | 20 | 5 | 0.06 | — |
Psychiatric group room | 50 | 5 | 0.06 | — |
Psychiatric seclusion room | 5 | 10 | 0.06 | — |
Speech therapy room | 20 | 5 | 0.06 | — |
Urgent care examination room | 20 | 7.5 | 0.12 | — |
Urgent care observation room | 20 | 5 | 0.06 | — |
Urgent care treatment room | 20 | 7.5 | 0.18 | — |
Urgent care triage room | 20 | 10 | 0.18 | — |
Private dwellings, single and multiple | ||||
Garages, common for multiple unitsb | — | — | — | 0.75 |
Kitchensb | — | — | — | 50/100f |
Living areasc | Based on number of bedrooms. First bedroom, 2; each additional bedroom, 1 | 0.35 ACH but not less than 15 cfm/person | — | — |
Toilet rooms and bathroomsg | — | — | — | 25/50f |
Public spaces | ||||
Corridors | — | — | 0.06 | — |
Courtrooms | 70 | 5 | 0.06 | — |
Elevator car | — | — | — | 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 | — |
Room with adult changing station | — | — | — | 50/70e |
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 | 2 | 10 | 0.12 | — |
Smoking loungesb | 70 | 60 | — | — |
Storage rooms | — | — | 0.12 | — |
Warehouses (see “Storage”) | — | 10 | 0.06 | — |
Specialty shops | ||||
Automotive motor fuel-dispensing stationsb | — | — | — | 1.5 |
Banks or lobbies | 15 | 7.5 | 0.06 | — |
Barber | 25 | 7.5 | 0.06 | 0.5 |
Beauty salonsb | 25 | 20 | 0.12 | 0.6 |
Embalming roomb | — | — | — | 2.0 |
Nail salons b, h | 25 | 20 | 0.12 | 0.6 |
Pet shops (animal areas)b | 10 | 7.5 | 0.18 | 0.9 |
Supermarkets | 8 | 7.5 | 0.06 | — |
Sports and amusement | ||||
Bowling alleys (seating areas) | 40 | 10 | 0.12 | — |
Disco/dance floors | 100 | 20 | 0.06 | — |
Game arcades | 20 | 7.5 | 0.18 | — |
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 |
Spectator areas | 150 | 7.5 | 0.06 | — |
Swimming pools (pool and deck area) | — | — | 0.48 | — |
Storage | ||||
Refrigerated warehouses/freezers (< 50°F) | — | 10 | — | — |
Repair garages, enclosed parking garagesb, d | — | — | — | 0.75 |
Warehousesl | — | 10 | 0.06 | — |
Theaters | ||||
Auditoriums (see “Education”) | — | — | — | — |
Lobbies | 150 | 5 | 0.06 | — |
Stages, studios | 70 | 10 | 0.06 | — |
Ticket booths | 60 | 5 | 0.06 | — |
Transportation | ||||
Platforms | 100 | 7.5 | 0.06 | — |
Transportation waiting | 100 | 7.5 | 0.06 | — |
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 |
Manufacturing where hazardous materials are not used | 7 | 10 | 0.18 | — |
Manufacturing where hazardous materials are used (excludes heavy industrial and chemical processes) | 7 | 10 | 0.18 | — |
Meat processingc | 10 | 15 | — | — |
Pharmacy (prep. area) | 10 | 5 | 0.18 | — |
Photo studios | 10 | 5 | 0.12 | — |
Sorting, packing, light assembly | 7 | 7.5 | 0.12 | — |
Telephone closets | — | — | 0.00 | — |
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 on net occupiable floor area.
- b.
- c.
Spaces unheated or maintained below 50°F are not covered by these requirements unless the occupancy is continuous.
- d.
- e.
Rates are per water closet, urinal or adult changing station. 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. For occupancies other than science laboratories, where there is a wheel-type energy recovery ventilation (ERV) unit in the exhaust system design, the volume of air leaked from the exhaust airstream into the outdoor airstream within the ERV shall be less than 10 percent of the outdoor air volume. 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 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.
- i.
Outpatient facilities to which the rates apply are freestanding birth centers, urgent care centers, neighborhood clinics and physicians’ offices, Class 1 imaging facilities, outpatient psychiatric facilities, outpatient rehabilitation facilities and outpatient dental facilities.
- j.
The requirements of this table provide for acceptable IAQ. The requirements of this table do not address the airborne transmission of airborne viruses, bacteria and other infectious contagions.
- k.
These rates are intended only for outpatient dental clinics where the amount of nitrous oxide is limited. They are not intended for dental operatories in institutional buildings where nitrous oxide is piped.
- l.
The occupiable floor area in warehouses shall not include the floor area of self-storage units, floor areas under rack storage or designated palletized storage floor areas.
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:
Zone floor area: the net occupiable floor area of the space or spaces in the zone.
Zone population: the number of people in the space or spaces in the zone.
The zone air distribution effectiveness (Ez) shall be determined using Table 403.3.1.1.1.2.
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 | 0.8 |
Makeup air drawn in near to the exhaust 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 4 1/2 feet of floor level.
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 403.3.1.1.2.3.4 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 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:
Primary airflow: The airflow rate supplied to the zone from the air-handling 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.
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 |
The uncorrected outdoor air intake flow rate (Vou) shall be determined in accordance with Equation 4-6.
where:
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.
403.3.1.3 System operation.
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. Where demand-controlled ventilation is employed to adjust the outdoor airflow rate based on the actual number of occupants present, the minimum quantity of outdoor air shall not fall below that determined from the area outdoor airflow rate column of Table 403.3.1.1 during periods when the building is expected to be occupied.
403.3.1.4 Variable air volume system control.
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.
403.3.2 Group R-2, R-3 and R-4 occupancies.
The design of local exhaust systems and ventilation systems for outdoor air in Group R-2, R-3 and R-4 occupancies shall comply with Sections 403.3.2.1 through 403.3.2.5.
403.3.2.1 Outdoor air for dwelling units.
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.
where:
outdoor airflow rate, cfm
conditioned floor area, ft2
number of bedrooms; not to be less than one
Exceptions:
- 1.
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 airflow rate over the 4-hour period shall be not less than that prescribed by Equation 4-9.
- 2.
The minimum mechanical ventilation rate determined in accordance with Equation 4-9 shall be reduced by 30 percent provided that both of the following conditions apply:
- 2.1.
A ducted system supplies ventilation air directly to each bedroom and to one or more of the following rooms:
- 2.1.1.
Living room.
- 2.1.2.
Dining room.
- 2.1.3.
Kitchen.
- 2.1.1.
- 2.2.
The whole-house ventilation system is a balanced ventilation system.
- 2.1.
403.3.2.2 Outdoor air for other spaces.
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 [0.0003 m3/(s × m2)] of floor area.
403.3.2.3 Local exhaust.
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.
AREA TO BE EXHAUSTED | EXHAUST RATE CAPACITY |
Kitchens | 100 cfm intermittent or 50 cfm continuous |
Bathrooms and toilet rooms | 50 cfm intermittent or 25 cfm continuous |
For SI: 1 cubic foot per minute = 0.0004719 m3/s.
403.3.2.4 System controls.
Where provided within a dwelling unit, controls for outdoor air ventilation systems shall include text or a symbol indicating the system’s function.
Section 404 Enclosed Parking Garages
404.1 Enclosed parking garages.
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 manufacturer’s instructions. Automatic operation shall cycle the ventilation system between the following two modes of operation:
- 1.
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.
- 2.
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.
Section 405 Systems Control
405.1 General.
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.
Section 406 Ventilation of Uninhabited Spaces
406.1 General.
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.