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Section 120.1 Requirements for Ventilation and Indoor Air Quality
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- All occupiable spaces in high-rise residential buildings, hotel/motel buildings, and nonresidential buildings other than healthcare facilities shall comply with the applicable requirements of Section 120.1(a) through 120.1(g). Healthcare facilities shall be ventilated in accordance with Chapter 4 of the California Mechanical Code.
- The required outdoor air-ventilation rate and the air-distribution system design shall be clearly identified on the plans in accordance with Section 10-103 of Title 24, Part 1.
- Mechanical space conditioning systems that supply air to an occupiable space through ductwork exceeding 10 feet (3 m) in length.
- Mechanical supply-only ventilation systems that provide outside air to an occupiable space.
- The supply side of mechanical balanced ventilation systems, including heat recovery ventilation systems and energy recovery ventilation systems that provide outside air to an occupiable space.
- Nominal 2-inch minimum depth filter(s) shall be sized by the system designer; or
- (Equation 120.1-A)
- All system air filters shall be located and installed in such a manner as to be accessible for regular service by the system owner.
- All system air filter installation locations shall be labeled to disclose the applicable design airflow rate and the maximum allowable clean-filter pressure drop. The labels shall be permanently affixed to the air filter installation location, readily legible, and visible to a person replacing the air filter.
- Air filter efficiency. The system shall be provided with air filter(s) having a designated efficiency equal to or greater than MERV 13 when tested in accordance with ASHRAE Standard 52.2, or a particle size efficiency rating equal to or greater than 50 percent in the 0.30—1.0 μm range and equal to or greater than 85 percent in the 1.0—3.0 μm range, when tested in accordance with AHRI Standard 680.
- The maximum allowable clean-filter pressure drop determined by the system design for the nominal two inch minimum depth air filter required by Section 120.1(b)1Biia; or
- A maximum of 25 Pa (0.1 in. of water) clean-filter pressure drop shall be allowed for a nominal 1-inch depth air filter sized according to Section 120.1(b)1Biib; or
- For system specified in 120.1(b)1Aii and 120.1(b)1Aiii, the maximum allowable clean filter pressure drop determined by the system design.
- Window operation is not a permissible method of providing the dwelling unit ventilation airflow specified in subsections iv or v below.
- Air filtration shall conform to the specifications in Section 120.1(b)1. Compliance with ASHRAE 62.2 Sections 6.7 (Minimum Filtration) and 6.7.1 (Filter Pressure Drop) shall not be required.
- (Equation 120.1-B)
- A balanced mechanical ventilation system shall provide the required dwelling-unit ventilation airflow.
- Continuously operating supply ventilation systems or continuous operating exhaust ventilation systems shall be allowed to be used to provide the required dwelling unit ventilation airflow if the dwelling-unit envelope leakage is less than or equal to 0.3 cubic feet per minute at 50 Pa (0.2 in. of water) per ft2 of dwelling unit envelope surface area as confirmed by field verification and diagnostic testing in accordance with Reference Nonresidential Appendix NA7.18.2.
- Multifamily building central ventilation systems that serve multiple dwelling-units shall be balanced to provide ventilation airflow to each dwelling-unit served at a rate equal to or greater than the rate specified by Equation 120.1-B, but not more than twenty percent greater than the specified rate. These systems shall utilize balancing means to ensure the dwelling unit airflows can be adjusted to meet this balancing requirement. These system balancing means may include but not be limited to constant air regulation devices, orifice plates, and variable speed central fans.
- Compliance with ASHRAE 62.2 Section 6.5.2 (Space Conditioning System Ducts) shall not be required.
- Compliance with ASHRAE 62.2 Section 4.4 (Control and Operation) shall require manual switches associated with dwelling unit ventilation systems to have a label clearly displaying the following text, or equivalent text: "This switch controls the indoor air quality ventilation for the home. Leave it on unless the outdoor air quality is very poor."
- Airflow performance. The dwelling-unit ventilation airflow required by Section 120.1(b)2Aiv or 120.1(b)2Av shall be confirmed through field verification and diagnostic testing in accordance with Reference Nonresidential Appendix NA7.18.1.
- The minimum ventilation airflow rate as specified in Section 5 of ASHRAE 62.2.
- Mechanical system types described in Section 120.1(b)1A shall be provided with air filters to clean the outside and return air prior to its introduction into occupied spaces.
- Air filter efficiency. The filters shall have a designated efficiency equal to or greater than MERV 13 when tested in accordance with ASHRAE Standard 52.2, or a particle size efficiency rating equal to or greater than 50 percent in the 0.30—1.0 μm range, and equal to or greater than 85 percent in the 1.0—3.0 μm range when tested in accordance with AHRI Standard 680; and
- Nominal 2-inch minimum depth filter(s); or
- Nominal 1-inch minimum depth filter(s) shall be allowed if the filter(s) are sized according to Equation 120.1-A, based on a maximum face velocity of 150 feet per minute.
- Single side opening. For spaces with operable opening on one side of the space, the maximum distance from the operable opening shall be not more than 2H. [ASHRAE 62.1:126.96.36.199]
- Double side opening. For spaces with operable openings on two opposite sides of the space, the maximum distance from the operable opening shall be not more than 5H. [ASHRAE 62.1:188.8.131.52]
- Corner opening. For spaces with operable openings on two adjacent sides of a space, the maximum distance from the operable openings shall be not more than 5H along a line drawn between the two openings that are the farthest apart. Floor area outside that line shall comply with i or ii. [ASHRAE 62.1:184.108.40.206]
- Location and size of openings. Spaces or portions of spaces to be naturally ventilated shall be permanently open to operable wall openings directly to the outdoors. The openable area shall be not less than 4 percent of the net occupiable floor area. Where openings are covered with louvers or otherwise obstructed, the openable area shall be based on the net free unobstructed area through the opening. Where interior rooms, or portions of rooms, without direct openings to the outdoors are ventilated through adjoining rooms, the opening between rooms shall be permanently unobstructed and have a free area of not less than 8 percent of the area of the interior room or less than 25 square feet. [ASHRAE 62.1:6.4.2]
- (Equation 120.1-F)
- (Equation 120.1-G)
- Use of transfer air is in accordance with Section 120.1(g); and
- The outdoor air that is supplied to all spaces combined, is sufficient to meet the requirements of Section 120.1(c)3 for each space individually.
- Exhaust ventilation. The design exhaust airflow shall be determined in accordance with the requirements in Table 120.1-B. Exhaust makeup air shall be permitted to be any combination of outdoor air, recirculated air, or transfer air. [ASHRAE 62.1:6.5.1]
- Pre-occupancy. The lesser of the minimum rate of outdoor air required by Section 120.1(c)2 or three complete air changes shall be supplied to the entire building during the one-hour period immediately before the building is normally occupied.
- CO2 sensors shall be located in the room between 3 feet and 6 feet above the floor or at the anticipated height of the occupants' heads.
- CO2 concentration shall be assumed to be 400 ppm without any direct measurement; or
- CO2 concentration shall be dynamically measured using a CO2 sensor located within 4 feet of the outdoor air intake.
- When the system is operating during hours of expected occupancy, the controls shall maintain system outdoor air ventilation rates no less than the rate listed in Table 120.1-A for DCV, times the conditioned floor area for spaces with CO2 sensors, plus the rate required by Section 120.1(c)3 for other spaces served by the system, or the exhaust air rate, whichever is greater.
- CO2 sensors shall be certified by the manufacturer to be accurate within plus or minus 75 ppm at a 600 and 1000 ppm concentration when measured at sea level and 25°C, factory calibrated and certified by the manufacturer to require calibration no more frequently than once every 5 years. Upon detection of sensor failure, the system shall provide a signal which resets to supply the minimum quantity of outside air to levels required by Section 120.1(c)3 to the zone serviced by the sensor at all times that the zone is occupied.
- The CO2 sensor(s) reading for each zone shall be displayed continuously, and shall be recorded on systems with DDC to the zone level.
- Occupant sensors shall meet the requirements in Section 110.9(b)4 and shall have suitable coverage and placement to detect occupants in the entire space ventilated. If occupant sensors controlling lighting are used for ventilation, the ventilation signal shall be independent of daylighting, manual lighting overrides or manual control of lighting. When a single zone damper or a single zone system serves multiple rooms, there shall be an occupancy sensor in each room and the zone is not considered vacant until all rooms in the zone are vacant.
- Within 5 feet of the unit; or
- Within 15 feet of the unit, substantially toward the unit, and at a velocity not less than 500 feet per minute.
- All mechanical ventilation and space-conditioning systems shall be designed with and have installed ductwork, dampers and controls to allow outside air rates to be operated at the larger of (1) the minimum levels specified in Section 120.1(c)3; or (2) the rate required for make-up of exhaust systems that are required for an exempt or covered process, for control of odors, or for the removal of contaminants within the space.
- All variable air volume mechanical ventilation and space-conditioning systems shall include dynamic controls that maintain measured outside air ventilation rates within 10 percent of the required outside air ventilation rate at both full and reduced supply airflow conditions. Fixed minimum damper position is not considered to be dynamic and is not an allowed control strategy.
- Measured outdoor air rates of constant volume mechanical ventilation and space-conditioning systems shall be within 10 percent of the required outside air rate.
- Class 1 air. Recirculation or transfer of Class 1 air to any space shall be permitted; [ASHRAE 62.1:220.127.116.11]
- Recirculation of Class 2 air within the space of origin shall be permitted [ASHRAE 62.1:18.104.22.168.1];
- Recirculation or transfer of Class 2 to other Class 2 or Class 3 spaces shall be permitted, provided that the other spaces are used for the same or similar purpose or task and involve the same or similar pollutant sources as the Class 2 space [ASHRAE 62.1:22.214.171.124.2]; or
- Transfer of Class 2 air to toilet rooms [ASHRAE 62.1:126.96.36.199.3]; or
- Recirculation or transfer of Class 2 air to Class 4 spaces [ASHRAE 62.1:188.8.131.52.4]; or
- Recirculation of Class 3 air within the space of origin shall be permitted. [ASHRAE 62.1:184.108.40.206.1]
- Class 4 air. Class 4 air shall not be recirculated or transferred to any space or recirculated within the space of origin. [ASHRAE 62.1:220.127.116.11]
- Ancillary spaces. Redesignation of Class 1 air to Class 2 air shall be permitted for Class 1 spaces that are ancillary to Class 2 spaces. [ASHRAE 62.1:18.104.22.168]
- Transfer. A mixture of air that has been transferred through or returned from spaces or locations with different air classes shall be redesignated with the highest classification among the air classes mixed. [ASHRAE 62.1:22.214.171.124]
- Classification. Air leaving each space or location shall be designated at an expected air-quality classification not less than that shown in Tables 120.1-A, 120.1-B or 120.1-C. Air leaving spaces or locations that are not listed in Tables 120.1-A, 120.1-B or 120.1-C shall be designated with the same classification as air from the most similar space or location listed in terms of occupant activities and building construction.
MINIMUM VENTILATION RATES
|OCCUPANCY CATEGORY||AREA OUTDOOR AIR RATE1 |
|MIN AIR RATE FOR DCV2 |
|Daycare (through age 4)||0.21||0.15||2|
|Classrooms (ages 5—8)||0.38||0.15||1|
|Classrooms (age 9—18)||0.38||0.15||1|
|Lecture hall (fixed seats)||—||0.15||1||F|
|Food and Beverage Service|
|Restaurant dining rooms||0.50||0.15||2|
|Bars, cocktail lounges||0.50||0.20||2|
|Occupiable storage rooms for liquids or gels||0.15||2||B|
|Hotels, Motels, Resorts, Dormitories|
|Barracks sleeping areas||0.15||1||F|
|Laundry rooms, central||0.15||2|
|Laundry rooms within dwelling units||0.15||1|
|Main entry lobbies||0.50||0.15||1||F|
|Occupiable storage rooms for dry materials||0.15||1|
|Bank vaults/safe deposit||0.15||2||F|
|Banks or bank lobbies||0.15||1||F|
|Computer (not printing)||0.15||1||F|
|Freezer and refrigerated spaces (< 50°F)||—||2||E|
|General manufacturing (excludes heavy industrial and process using chemicals)||0.15||3|
|Pharmacy (prep. Area)||0.15||2|
|Sorting, packing, light assembly||0.15||2|
|Public Assembly Spaces|
|Auditorium seating area||1.07||0.15||1||F|
|Places of religious worship||1.07||0.15||1||F|
|Libraries (reading rooms and stack areas)||0.15||1|
|Sales (except as below)||0.25||0.20||2|
|Mall common areas||0.25||0.15||1||F|
|Beauty and nail salons||0.40||2|
|Pet shops (animal areas)||0.25||0.15||2|
|Sports and Entertainment|
|Gym, sports arena (play area)||0.50||0.15||2||E|
|Health club/aerobics room||0.15||2|
|Health club/weight rooms||0.15||2|
|Bowling alley (seating)||1.07||0.15||1|
|Stages, studios||0.50||0.15||1||D, F|
- Ra was determined as being the larger of the area method and the default per person method. The occupant density used in the per person method was assumed to be one half of the maximum occupant load assumed for egress purposes in the CBC.
- If this column specifies a minimum cfm/ft2, then it shall be used to comply with Section 120.1(d)4E.
- For high-school and college libraries, the values shown for "Public Assembly Spaces — Libraries" shall be used.
- Rate may not be sufficient where stored materials include those having potentially harmful emissions.
- Rate does not allow for humidity control. "Deck area" refers to the area surrounding the pool that is capable of being wetted during pool use or when the pool is occupied. Deck area that is not expected to be wetted shall be designated as an occupancy category.
- Rate does not include special exhaust for stage effects such as dry ice vapors and smoke.
- Where combustion equipment is intended to be used on the playing surface or in the space, additional dilution ventilation, source control, or both shall be provided.
- Ventilation air for this occupancy category shall be permitted to be reduced to zero when the space is in occupied-standby mode.
TABLE 120.1-B — MINIMUM EXHAUST RATES
[ASHRAE 62.1: TABLE 6.5]
|OCCUPANCY CATEGORY||EXHAUST RATE, |
|EXHAUST RATE2 |
|Auto repair rooms||—||1.5||2||A|
|Beauty and nail salons||—||0.60||2|
|Cells with toilet||—||1.00||2|
|Copy, printing rooms||—||0.50||2|
|Educational science laboratories||—||1.00||2|
|Janitor closets, trash rooms, recycling||—||1.00||3|
|Kitchens — commercial||—||0.70||2|
|Locker rooms for athletic or industrial facilities||—||0.50||2|
|All other locker rooms||—||0.25||2|
|Paint spray booths||—||—||4||F|
|Pet shops (animal areas)||—||0.90||2|
|Refrigerating machinery rooms||—||-||3||F|
|Soiled laundry storage rooms||—||1.00||3||F|
|Storage rooms, chemical||—||1.50||4||F|
|Toilets — private||25/50||—||2||E|
|Toilets — public||50/70||—||2||D|
- Stands where engines are run shall have exhaust systems that directly connect to the engine exhaust and prevent escape of fumes.
- Where combustion equipment is intended to be used on the playing surface, additional dilution ventilation, source control, or both shall be provided.
- Exhaust shall not be required where two or more sides comprise walls that are at least 50% open to the outside.
- Rate is per water closet, urinal, or both. Provide the higher rate where periods of heavy use are expected to occur. The lower rate shall be permitted to be used otherwise.
- Rate is for a toilet room intended to be occupied by one person at a time. For continuous systems operation during hours of use, the lower rate shall be permitted to be used. Otherwise the higher rate shall be used.
- See other applicable standards for exhaust rate.
- For continuous system operation, the lower rate shall be permitted to be used. Otherwise the higher rate shall be used.
- Rate is per showerhead
TABLE 120.1-C — AIRSTREAMS OR SOURCES
[ASHRAE 62.1:TABLE 5.16.1]
|Diazo printing equipment discharge||4|
|Commercial kitchen grease hoods||4|
|Commercial kitchen hoods other than grease||3|
|Hydraulic elevator machine room||2|
- Air Class 4 unless determined otherwise by the Environmental Health and Safety professional responsible to the owner or to the owner's designee.