CMC · California Mechanical Code
Kitchen and bathroom exhaust requirements in residential occupancies
Bathrooms with tubs/showers must have mechanical exhaust to the outdoors and meet minimum fan rates (50 cfm intermittent or 25 cfm continuous); kitchens must have exhaust that vents outdoors and an accessible control (the CMC requires outdoor discharge and controls but does not list a kitchen cfm in §405.4).
Last reviewed: July 6, 2026
What the code requires — plain English
- Provide a mechanical exhaust that discharges directly to the outdoors in each kitchen and in every room containing a bathtub, shower, or tub/shower combination. This is required by §405.4 (kitchens) and §405.3 (bathrooms) of the California Mechanical Code.
- For bathrooms the CMC sets minimum exhaust rates: 50 ft³/min (23.6 L/s) for intermittent operation and 25 ft³/min (11.8 L/s) for continuous operation per §405.3.1.
The single most important rule: every bathroom with a tub/shower must have a mechanical exhaust to outdoors (manual or automatic control) and meet the minimum fan rates in §405.3.1.
Requirements in detail
Key defined terms (first use)
- Mechanical exhaust — a fan or hood that moves room air to the outdoors (not simply an operable window) per §405.3 and §405.4.
- Intermittent — fan operated as needed (manual ON/OFF or automatic demand control). Continuous — fan runs continuously (both options are addressed in the sections below). §405.3 and §405.4 require a readily accessible manual control for intermittent operation.
Decision table — what you must provide
| Space | Required discharge | Controls required | Minimum rate (intermittent) | Minimum rate (continuous) | Code Reference |
|---|---|---|---|---|---|
| Bathroom (room containing bathtub/shower/tub‑shower) | Exhaust to outdoors | Readily accessible manual control or automatic control for intermittent; continuous allowed | 50 ft³/min (23.6 L/s) | 25 ft³/min (11.8 L/s) | §405.3 and §405.3.1 |
| Kitchen (each dwelling‑unit kitchen) | Exhaust to outdoors | Readily accessible manual control or automatic control for intermittent; continuous allowed | No specific CMC cfm given in §405.4 — supply only the exhaust-to-outdoors + controls | No specific CMC cfm given in §405.4 | §405.4 (text requires exhaust to outdoors; rates not specified in §405.4) |
| Ventilation openings (location/termination) | See CMC text for specifics | — | — | — | §405.5 (see note — full text not present in the uploaded files) |
Notes:
- The CMC explicitly gives numerical exhaust rates only for bathrooms in §405.3.1. The CMC text for kitchen exhaust in §405.4 mandates outdoor discharge and controls but does not specify a numeric cfm requirement in that section; energy/efficiency or other code sections (e.g., Title 24/energy code or ASHRAE 62.2) provide more detailed kitchen airflow guidance elsewhere.
Controls and operation
- Intermittent systems must have a readily accessible manual control or an automatic control; continuous systems are permitted. (See §405.3 and §405.4.)
Exception(s) called out in the CMC
- Kitchen: Recirculating (non‑vented) systems are an exception only if installed in accordance with Section 516.0 and the manufacturer's instructions (that exception appears in §405.4). If you plan a recirculating hood, confirm it meets those criteria.
Exceptions & special cases
- Recirculating kitchen hoods are allowed as an exception to the outdoor discharge requirement in §405.4, but only per §516.0 and the manufacturer’s instructions. Verify listing/installation criteria before accepting recirculation.
- The CMC bathroom requirements are cross‑referenced with CALGreen and the California Residential Code (which also states that window operation is not permitted as the sole method for humidity control in bathrooms). See Residential Code R325.2.1 for that note.
- The uploaded files include a table of contents showing §405.5 Ventilation Openings, but the full text of §405.5 was not present in the provided excerpts, so specific rules about termination/clearances from §405.5 cannot be quoted here. Do not rely on this summary for any detailed termination or opening‑location rule from §405.5 — obtain the full §405.5 text from the adopted code or AHJ.
Common mistakes
- Assuming the CMC gives a numeric kitchen exhaust cfm in §405.4 — it does not; §405.4 requires outdoor discharge and controls but no cfm is specified there. For kitchen cfm/capture efficiency, consult Title 24 (Energy Code) or ASHRAE 62.2.
- Using a window to meet bathroom humidity control — window operation is not an acceptable substitute where mechanical exhaust is required (see Residential Code cross‑references).
- Installing a recirculating hood and assuming it meets the §405.4 requirement — the CMC allows an exception only when installed per §516.0 and the manufacturer’s instructions; otherwise the hood must vent outdoors.
- Omitting a manual control for intermittent fans — §405.3 and §405.4 require a readily accessible manual control (or automatic control that does not impede occupant ON control) for intermittent operation.
Worked example
Scenario: A single bathroom (with a tub/shower) in a detached dwelling. The owner wants an intermittent exhaust fan.
Steps applied to code:
- Identify controlling section: §405.3 requires mechanical exhaust to outdoors for rooms with a tub/shower; §405.3.1 sets rates.
- Choose operation mode: intermittent (on demand). Per §405.3.1, the fan must be at least 50 ft³/min (23.6 L/s).
- Provide control: install a readily accessible manual ON/OFF switch or an automatic control that permits occupant ON. §405.3 requires the control.
- Discharge: duct the fan to terminate directly to the outdoors (no recirculation), per §405.3.
Result: Install a listed exhaust fan rated at ≥50 cfm at the operating static pressure, with an accessible switch near the door, and duct to an outdoor termination that complies with the mechanical termination/clearance requirements (see §405.5 — obtain full text for clearance rules).
Conversion quick‑reference used above:
- 50 ft³/min = 23.6 L/s; 25 ft³/min = 11.8 L/s (values shown in §405.3.1).
Related provisions (CMC & cross‑references)
- §405.1 — General ventilation for residential occupancies (sets the Chapter 405 scope).
- §405.2 — Ventilation air rate calculation for whole dwelling ventilation (Equation 405.2).
- §405.3 — Bathroom Exhaust (requires mechanical exhaust to outdoors; see also §405.3.1).
- §405.3.1 — Bathroom Exhaust Rate (50 cfm intermittent / 25 cfm continuous).
- §405.4 — Kitchen Exhaust (requires outdoor discharge and controls; contains exception for recirculating systems per §516.0).
- §405.5 — Ventilation Openings (table of contents shows the section exists; full text not in provided excerpts).
- Residential Code cross‑reference: R325.2.1 — bathroom exhaust fans and the prohibition on window operation as the sole method for humidity control (references the CMC).
If you want, I can:
- Pull and quote the full text of §405.5 (ventilation opening/termination rules) from the adopted CMC if you upload that specific excerpt or permit me to fetch the authoritative code text; or
- Map kitchen exhaust requirements to Title 24 / ASHRAE 62.2 so you get the numeric cfm / capture‑efficiency requirements that the CMC section itself defers to elsewhere.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 5.08 High relevance — show source text
minute per square foot = 5.08 [(L/s)/m [2] ]
405.0 Ventilation for Residential Occupancies.
405.1 General. Rooms or occupied spaces within residential occupancies, where the occupants are nontransient, shall be designed to have mechanical ventilation and exhaust air in accordance with Section 405.2 through Section 405.5.
405.1.1 Natural Ventilation. Where approved by the Authority Having Jurisdiction, natural ventilation shall be permitted for Climate Zone 1, Climate Zone 2, or for thermally conditioned buildings for less than 876 hours
per year.
405.2 Ventilation Air Rate. The required mechanical ventilation outdoor air rate ( Qtot ) shall be as calculated in accordance with Equation 405.2.
Exception: For existing buildings and where permitted by the Authority Having Jurisdiction, the total mechanical ventilation ( Qtot ) is not required where Qtot is calculated to be less than 15 ft [3] /min (7.08 L/s).
Qtot = 0.03 Afloor + 7.5 ( Nbr + 1) (Equation 405.2)
Where:
Qtot = Total required ventilation outdoor air rate, CFM (L/s) Afloor = Floor area, ft [2] (m [2] ) Nbr = Number of bedrooms more than 1
For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s
405.2.1 Reduced Ventilation Air Rate. Where permitted by the Authority Having Jurisdiction, the mechanical ventilation air rate required in Section 405.2 shall be permitted to be reduced where an infiltration rate is determined in accordance with ASTM E779.
405.3 Bathroom Exhaust. A mechanical exhaust directly to the outdoors shall be provided in each room containing a bathtub, shower, or tub/shower combination. The fan shall run intermittently (on demand) or continuously. A readily accessible manual control designed to be operated as needed or an automatic control shall be provided for intermittent operations. [HCD 1 & HCD 2] Each bathroom shall also be mechanically ventilated in accordance with Division 4.5 of the California Green Building Standards Code (CALGreen).
405.3.1 Exhaust Rate. The exhaust rate shall be not less than 50 ft [3] /min (23.6 L/s) for intermittent operation and 25 ft [3] /min (11.8 L/s) for continuous operation. 405.4 Kitchen Exhaust. A mechanical exhaust system that discharges directly to the outdoors shall be provided in each kitchen. The fan shall run intermittently (on demand) or continuously. A readily accessible manual control designed to be operated as needed or an automatic control shall be provided for intermittent operations.
Exception: Recirculating systems installed in accordance with Section 516.0 and the manufacturer’s installation
instructions.
CMC § 150.0 High relevance — show source text
TABLE 150.0-E—DEMAND-CONTROLLED LOCAL VENTILATION EXHAUST AIRFLOW RATES AND CAPTURE EFFICIENCY Col2 APPLICATION COMPLIANCE CRITERIA Enclosed Kitchen or Nonenclosed Kitchen Vented range hood, including appliance-range hood combinations, shall meet either the
capture efficiency (CE) or the airflow rate specified in Table 150.0-G as applicable.Enclosed Kitchen or Nonenclosed Kitchen Other kitchen exhaust fans, including downdraft: 300 cfm (150 L/s) Bathroom 50 cfm (25 L/s) iv. Continuous mechanical exhaust. A mechanical exhaust system shall be installed to operate continuously. The system may be part of a balanced mechanical ventilation system. a. Control and operation . A manual ON-OFF control shall be provided for each continuous mechanical exhaust system. The system shall be designed to operate during all occupiable hours. The ON-OFF control shall be accessible to the dwelling unit occupant.
b. Ventilation rate. The minimum delivered ventilation shall be at least the amount indicated in Table 150.0-F during each hour of operation.
TABLE 150.0-F—CONTINUOUS LOCAL VENTILATION EXHAUST AIRFLOW RATES Col2 APPLICATION AIRFLOW Enclosed kitchen 5 ACH, based on kitchen volume Bathroom 20 cfm (10 L/s) TABLE 150.0-G—KITCHEN RANGE HOOD AIRFLOW RATES (CFM) AND ASTM E3087 CAPTURE EFFICIENCY (CE)
RATINGS ACCORDING TO DWELLING UNIT FLOOR AREA AND KITCHEN RANGE FUEL TYPECol2 Col3 **DWELLING UNIT FLOOR AREA (ft2) ** HOOD OVER ELECTRIC RANGE HOOD OVER NATURAL GAS RANGE >1500 50% CE or 110 cfm 70% CE or 180 cfm >1000–1500 50% CE or 110 cfm 80% CE or 250 cfm 750–1000 55% CE or 130 cfm 85% CE or 280 cfm <750 65% CE or 160 cfm 85% CE or 280 cfm v. Airflow measurement of local mechanical exhaust by the system installer. The airflow required by Section 150.0(o)1G is the quantity of indoor air exhausted by the ventilation system as installed in the dwelling unit. When a vented range hood utilizes a capture efficiency rating to demonstrate compliance with Section
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150.0(o)1Giiib, the airflow listed in the approved directory corresponding to the compliant capture efficiency rating point shall be met by the installed system. The as-installed airflow shall be verified by the system installer to ensure compliance by use of either Subsection a or b below: a. The system installer shall measure the airflow by using a flow hood, flow grid or other airflow measuring device at the mechanical ventilation fan’s inlet terminals/grilles or outlet terminals/grilles in accordance with the procedures in Reference Residential Appendix RA3.7.
CMC § 62.2 High relevance — show source text
c. Replacement ventilation fans. Whole-dwelling unit replacement ventilation fans shall be rated for airflow and sound in accordance with the requirements of ASHRAE 62.2 Sections 7.1 and 7.3. Additionally, when conformance to a specified whole-dwelling unit airflow rate is required for compliance, the replacement fans shall be rated at no less than the airflow rate required for compliance. d. Air filters . If the air filtration device for a whole-dwelling unit ventilation system is altered or replaced, then one of the following Subsections 1 or 2 shall be used for compliance.
- Dwellings that were required by a previous building permit to comply with the ventilation system air filtration requirements in Section 160.2(b)1, 120.1(b)1 or 150.0(m)12 shall comply with the air filtration requirements in Section 160.2(b)1.
- Dwellings that were not required by a previous building permit to comply with the ventilation system air filtration requirements in Section 160.2(b)1, 120.1(b)1 or 150.0(m)12 shall not be required to comply with the air filtration requirements specified in Section 160.2(b)1.
ii. Local mechanical exhaust .
a. Bathroom local mechanical exhaust . Altered bathroom local mechanical exhaust systems shall comply with the applicable requirements specified in Section 160.0(b)2Avi. b. Kitchen local mechanical exhaust . If the kitchen local ventilation fan is altered or replaced, then one of the following Subsections 1, 2 or 3 shall be used for compliance.
- Dwellings that were required by a previous building permit to comply with the kitchen local exhaust requirements in Section 160.0(b)2Avi, 120.1(b)2vi or 150.0(o)1G shall meet or exceed the applicable airflow or capture efficiency requirements in Section 160.0(b)2Avi.
- Dwellings that were required by a previous building permit to install a vented kitchen range hood or other kitchen exhaust fan shall install a replacement fan that meets or exceeds the airflow required by the previous building permit, or 100 cfm, whichever is greater.
- Dwellings that were not required to have a kitchen local ventilation exhaust system according to the conditions in either Subsection 1 or 2 above shall not be required to comply with the requirements of Section 160.0(b)2Avi.
c. Replacement ventilation fans. New or replacement local mechanical exhaust fans shall be rated for airflow and sound in accordance with the requirements of ASHRAE 62.2 Section 7.1 and Title 24, Part 6, Section 160.0(b)2Avif. Additionally, when compliance with a specified exhaust airflow rate is required, the replacement fan shall be rated at no less than the airflow rate required for compliance.
(c) Performance approach. The altered component(s) and any newly installed equipment serving the alteration shall meet the applicable requirements of Subsections 1, 2 and 3 below. The energy budget for alterations is expressed in terms of long-term system cost (LSC) energy.
- The altered components shall meet the applicable requirements of Sections 110.0 through 110.9, 160.0, 160.1, 160.2(c) and (d), 160.3(a) through 160.3(b)5J, 160.3(b)6, 160.3(c), and 160.5.
CMC § 160.2 High relevance — show source text
a. Designers shall specify a design ventilation airflow rate for each dwelling unit that is equal to or greater than the rate specified by Equation 160.2-B. b. The design ventilation airflow rate for each dwelling unit shall be stated on the building design plans approved by the enforcement agency. c. Airflow in each dwelling unit shall be no more than 20 percent greater than the specified design ventilation airflow rate. Ventilation systems shall utilize mechanical or software airflow control means to ensure each of the dwelling-unit airflows can be maintained at the design ventilation airflow within this tolerance at all times. System airflow control-means may include but are not limited to constant air regulation devices, orifice plates and variable speed central fans. vi. Local mechanical exhaust. A local mechanical exhaust system shall be installed in each kitchen and bathroom. Systems shall be rated for airflow in accordance with ASHRAE 62.2 Section 7.1. a. Nonenclosed kitchens shall have a demand-controlled mechanical exhaust system meeting the requirements of Section 160.2(b)2Avic. b. Enclosed kitchens and all bathrooms shall have either one of the following options 1 or 2:
A demand-controlled mechanical exhaust system meeting the requirements of Section 160.2(b)2Avic; or
A continuous mechanical exhaust system meeting the requirements of Section 160.2(b)2Avid. c. Demand-controlled mechanical exhaust. A local mechanical exhaust system shall be designed to be operated as needed.
Control and operation. Demand-controlled mechanical exhaust systems shall be provided with at least one of the following controls: A. A readily accessible occupant-controlled ON-OFF control. B. An automatic control that does not impede occupant ON control.
Ventilation rate and capture efficiency. The system shall meet or exceed either the minimum airflow in accordance with Table 160.2-E or the minimum capture efficiency in accordance with Table 160.2-E, and Table 160.2-G. Capture efficiency ratings shall be determined in accordance with ASTM E3087, and listed in a product directory approved by the Energy Commission. d. Continuous mechanical exhaust. A mechanical exhaust system shall be installed to operate continuously. The system may be part of a balanced mechanical ventilation system.
Control and operation . A manual ON-OFF control shall be provided for each continuous mechanical exhaust system. The system shall be designed to operate during all occupiable hours. For multifamily dwelling units, the manual ON-OFF control may be accessible to the dwelling unit occupant; however, the manual ON-OFF control shall not be required to be accessible to the dwelling unit occupant.
Ventilation rate. The minimum delivered ventilation shall be at least the amount indicated in Table 160.2-F during each hour of operation. e. Airflow measurement of local mechanical exhaust by the system installer. The airflow required by Section 160.2(b)2Avi is the quantity of indoor air exhausted by the ventilation system as installed in the dwelling unit. When a vented range hood utilizes a capture efficiency rating to demonstrate compliance with Section 160.2(b)2Avic2, the airflow listed in the approved directory corresponding to the compliant capture efficiency rating point shall be met by the installed system. The as-installed airflow shall be verified by the system installer to ensure compliance by use of either Subsection 1 or 2 below:
CMC § 403.9 High relevance — show source text
Table 403.9 Airstreams or Sources
Description Air Class . . . . . . . . . . . 75
403.10 Air Balance . . . . . . . . . . . . . . . . . . . 75
404.0 Alternative Procedure for
Multiple-Zone Systems Ventilation Efficiency . . . . . . . . . . . 76
xxx
404.1 System Ventilation Efficiency . . . . . 76
404.2 Average Outdoor Air Fraction. . . . . 76
404.3 Zone Ventilation Efficiency . . . . . . . 76
405.0 Ventilation for Residential
Occupancies. . . . . . . . . . . . . . . . . . 77
405.1 General. . . . . . . . . . . . . . . . . . . . . . 77
405.2 Ventilation Air Rate. . . . . . . . . . . . . 77
405.3 Bathroom Exhaust . . . . . . . . . . . . . 77
405.4 Kitchen Exhaust . . . . . . . . . . . . . . . 77
405.5 Ventilation Openings . . . . . . . . . . . 77
406.0 Evaporative Cooling System for Health Care Facilities . . . . . . . . 78
407.0 Ventilation System Details . . . . . . . 78
407.1 General. . . . . . . . . . . . . . . . . . . . . . 78
407.2 Outdoor Air Intakes and
Exhaust Outlets . . . . . . . . . . . . . . . 78
407.3 Air Balance. . . . . . . . . . . . . . . . . . . 78
407.4 Air Circulation . . . . . . . . . . . . . . . . . 78
407.5 Variable Air Volume . . . . . . . . . . . . 79
407.6 Economizers. . . . . . . . . . . . . . . . . . 79
407.7 Unoccupied Turndown. . . . . . . . . . 79
407.8 Building Pressurization . . . . . . . . . 80
408.0 Filters . . . . . . . . . . . . . . . . . . . . . . . 80
408.1 General. . . . . . . . . . . . . . . . . . . . . . 80
408.2 Filters for Hospitals. . . . . . . . . . . . . 80
408.3 Filters for Skilled Nursing Facilities, Intermediate Care Facilities, and Correctional
Treatment Centers . . . . . . . . . . . . . 80
408.4 Filters for Outpatient Facilities . . . . 80
408.5 Filters for Recirculating
Room Units. . . . . . . . . . . . . . . . . . . 80
CMC § 120.1 High relevance — show source text
Provide the higher rate where periods of heavy use are expected to occur. The lower rate shall be permitted to be used otherwise.
E – 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.
F – See other applicable standards for exhaust rate.
G – For continuous system operation, the lower rate shall be permitted to be used. Otherwise the higher rate shall be used.
H – Rate is per showerhead.
Notes:
1. For spaces not included in this table, the spaces in Table 120.1-B shall apply.|A – RESERVED.
B – RESERVED.
C – Exhaust shall not be required where two or more sides comprise walls that are at least 50 percent open to the outside.
D – 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.
E – 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.
F – See other applicable standards for exhaust rate.
G – For continuous system operation, the lower rate shall be permitted to be used. Otherwise the higher rate shall be used.
H – Rate is per showerhead.
Notes:
1. For spaces not included in this table, the spaces in Table 120.1-B shall apply.|TABLE 160.2-D—AIRSTREAMS OR SOURCES
[ASHRAE 62.1:TABLE 6-3]Col2 DESCRIPTION AIR CLASS Commercial kitchen grease hoods 4 Commercial kitchen hoods other than grease 3 Hydraulic elevator machine room 2 Refrigerating machinery rooms 3 TABLE 160.2-E—DEMAND-CONTROLLED LOCAL VENTILATION EXHAUST AIRFLOW RATES AND CAPTURE EFFICIENCY Col2 APPLICATION COMPLIANCE CRITERIA Enclosed kitchen or nonenclosed kitchen Vented range hood, including appliance-range hood combinations shall meet either the capture
efficiency (CE) or the airflow rate specified in Table 160.2-G, as applicable.Enclosed kitchen or nonenclosed kitchen Other kitchen exhaust fans, including downdraft: 300 cfm (150 L/s). Bathroom 50 cfm (25 L/s) 210 2025 CALIFORNIA ENERGY CODE
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MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS
TABLE 160.2-F—CONTINUOUS LOCAL VENTILATION EXHAUST AIRFLOW RATES Col2 APPLICATION AIRFLOW Enclosed kitchen 5 ach, based on kitchen volume Bathroom 20 cfm (10 L/s) CMC § 62.2 High relevance — show source text
b. Replacement ventilation fans. Whole-dwelling unit replacement ventilation fans shall be rated for airflow and sound in accordance with the requirements of ASHRAE 62.2 Sections 7.1 and 7.3. Additionally, when conformance to a specified whole-dwelling unit airflow rate is required for compliance, the replacement fans shall be rated at no less than the airflow rate required for compliance. c. Air filters. If the air filtration device for a whole-dwelling unit ventilation system is altered or replaced, then one of the following Subsections 1 or 2 shall be used for compliance as applicable.
Dwellings that were required by a previous building permit to comply with the ventilation system air filtration requirements in Section 150.0(m)12 shall comply with the air filtration requirements in Section 150.0(m)12.
Dwellings that were not required by a previous building permit to comply with the ventilation system air filtration requirements in Section 150.0(m)12 shall not be required to comply with the air filtration requirements specified in Section 150.0(m)12.
ii. Local mechanical exhaust.
a. Bathroom local mechanical exhaust. Altered bathroom local mechanical exhaust systems shall comply with the applicable requirements specified in Section 150.0(o)1G. b. Kitchen local mechanical exhaust. If the kitchen local ventilation fan is altered or replaced, then one of the following Subsections 1, 2 or 3 shall be used for compliance as applicable.
- Dwellings that were required by a previous building permit to comply with the kitchen local exhaust requirements in Section 150.0(o)1G shall meet or exceed the applicable airflow or capture efficiency requirements in Section 150.0(o)1G.
- Dwellings that were required by a previous building permit to install a vented kitchen range hood or other kitchen exhaust fan shall install a replacement fan that meets or exceeds the airflow required by the previous building permit, or 100 cfm, whichever is greater.
- Dwellings that were not required to have a kitchen local ventilation exhaust system according to the conditions in either Subsection 1 or 2 above shall not be required to comply with the requirements of Section 150.0(o)1G.
c. Replacement ventilation fans. New or replacement local mechanical exhaust fans shall be rated for airflow and sound in accordance with the requirements of ASHRAE 62.2 Section 7.1 and Title 24, Part 6 Section 150.0(o)1Gvi. Additionally, when compliance with a specified exhaust airflow rate is required, the replacement fan shall be rated at no less than the airflow rate required for compliance.
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SINGLE-FAMILY RESIDENTIAL BUILDINGS—ADDITIONS AND ALTERATIONS TO EXISTING RESIDENTIAL BUILDINGS
N. Exterior doors. Alterations that add exterior door area shall meet the U -factor requirement of Section 150.1(c)5. 2. Performance approach. The energy budget for alterations is expressed in terms of long-term system cost (LSC), and the altered component(s) and any newly installed equipment serving the alteration shall meet the applicable requirements of Subsections A, B, and C below.
CMC § 2025 High relevance — show source text
The building’s structural stability is protected by the regulations for cutting and notching of structural members.
Chapter 4 Ventilation Air. Chapter 4 regulates the minimum requirements for ventilation air supply, exhaust, and makeup air for occupiable spaces within a building. Building ventilation is one important factor affecting the relationship between airborne transmission of respiratory infections and the health and productivity of workers. Ventilation air may be composed of mechanical or natural ventilation, infiltration, recirculated air, transfer air, or a suitable combination of these. Providing a comfortable and healthy indoor environment for building occupants is of primary concern. When determining ventilation rates, typical and unusual significant sources of indoor pollution need to be controlled. Areas such as kitchens, bathrooms, and laundries are all built to allow specific functions. These spaces produce pollutants such as moisture, odors, volatile organic compounds, particles, or combustion byproducts. The purpose of local exhaust is to control concentrates of these pollutants in the room into which they were emitted and to reduce the spread of pollutants into other parts of the occupancy. Local exhaust ventilation is the source control for pollution that is expected in certain rooms. Using local exhaust to extract contaminants before they mix with the indoor environment is essential.
Chapter 5 Exhaust Systems. Chapter 5 regulates the minimum requirements for exhaust systems. Chapter 5 contains two parts: Part I provides exhaust requirements for environmental air ducts and product conveying systems; Part II provides exhaust requirements for commercial hoods and kitchen ventilation. Environmental air ducts include exhaust ducts used for transporting the air from domestic kitchens, bathrooms, shower rooms, locker rooms, janitor’s closets, and clothes dryers. Systems that carry nonabrasive exhaust, such as smoke, moderate abrasives such as sawdust, and high abrasives such as manganese or acid vapors use product-conveying ducts. Part II provides the minimum fire safety requirements related to the design, installation, inspection, and maintenance of grease-type operations, such as cooking, for both fuel-gas and solid fuel. Cooking produces a significant amount of smoke, fumes, vapors, heat, and other pollutants. Therefore, acceptable kitchen ventilation is necessary to prevent fires from the build-up of grease and to provide the occupants protection from smoke, unpleasant odors, pollutants, and dangerous gases. There are two types of exhaust hoods (Type I and Type II) used in commercial kitchen applications.
xiv 2025 CALIFORNIA MECHANICAL CODE
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FORMAT OF THE UNIFORM MECHANICAL CODE
Type I hoods are intended to be installed above equipment or appliances that generate grease or smoke. Type II hoods are intended to be installed above equipment or appliances that generate steam, vapor, heat, or odors and do not generate grease or smoke.
Chapter 6 Duct Systems. Chapter 6 regulates requirements for ducts and plenums that are portions of a heating, cooling, ventilation, or exhaust system. This chapter contains material and installation requirements for metal, gypsum, factory-made, flexible, and plastic ducts. It also contains provisions for duct insulation, dampers, fire protection, and automatic shutoff for the building’s air distribution system. It is worth noting that exhaust ducts are regulated by Chapter 5, and combustion air ducts are regulated by Chapter 7.
CMC § 120.1 High relevance — show source text
For spaces not included in this table, the spaces in Table 120.1-B shall apply.|
TABLE 160.2-D—AIRSTREAMS OR SOURCES
[ASHRAE 62.1:TABLE 6-3]Col2 DESCRIPTION AIR CLASS Commercial kitchen grease hoods 4 Commercial kitchen hoods other than grease 3 Hydraulic elevator machine room 2 Refrigerating machinery rooms 3 TABLE 160.2-E—DEMAND-CONTROLLED LOCAL VENTILATION EXHAUST AIRFLOW RATES AND CAPTURE EFFICIENCY Col2 APPLICATION COMPLIANCE CRITERIA Enclosed kitchen or nonenclosed kitchen Vented range hood, including appliance-range hood combinations shall meet either the capture
efficiency (CE) or the airflow rate specified in Table 160.2-G, as applicable.Enclosed kitchen or nonenclosed kitchen Other kitchen exhaust fans, including downdraft: 300 cfm (150 L/s). Bathroom 50 cfm (25 L/s) 210 2025 CALIFORNIA ENERGY CODE
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MULTIFAMILY BUILDINGS—MANDATORY REQUIREMENTS
TABLE 160.2-F—CONTINUOUS LOCAL VENTILATION EXHAUST AIRFLOW RATES Col2 APPLICATION AIRFLOW Enclosed kitchen 5 ach, based on kitchen volume Bathroom 20 cfm (10 L/s) TABLE 160.2-G—KITCHEN RANGE HOOD AIRFLOW RATES (cfm) AND ASTM E3087 CAPTURE EFFICIENCY (CE) RATINGS
ACCORDING TO DWELLING UNIT FLOOR AREA AND KITCHEN RANGE FUEL TYPECol2 Col3 **DWELLING UNIT FLOOR AREA (FT2) ** HOOD OVER ELECTRIC RANGE HOOD OVER NATURAL GAS RANGE > 1500 50% CE or 110 cfm 70% CE or 180 cfm > 1000–1500 50% CE or 110 cfm 80% CE or 250 cfm 750–1000 55% CE or 130 cfm 85% CE or 280 cfm < 750 65% CE or 160 cfm 85% CE or 280 cfm TABLE 160.2-H—PRESCRIPTIVE VENTILATION SYSTEM DUCT SIZING [ASHRAE 62.2:TABLE 5-3] Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 Col12 Col13 Col14 Fan airflow rating,
cfm at minimum static
pressuref 0.25 in.CMC § 4.2 High relevance — show source text
For the purpose of this section, the exhaust from dwelling unit toilet rooms, bathrooms and kitchens shall not be considered as hazardous or noxious.
Exceptions:
The 10-foot (3048 mm) separation is not required where the intake opening is located 3 feet (914 mm) or greater below the contaminant source.
Vents and chimneys serving fuel-burning appliances shall be terminated in accordance with the applicable provisions of the California Mechanical Code.
Clothes dryer exhaust ducts shall be terminated in accordance with the California Mechanical Code.
R325.4.2 Exhaust openings. Exhaust air shall not be directed onto walkways.
R325.5 Outside opening protection. Air exhaust and intake openings that terminate outdoors shall be protected with corrosionresistant screens, louvers or grilles having an opening size of not less than [1] / 4 inch (6 mm) and a maximum opening size of [1] / 2 inch (13 mm), in any dimension. Openings shall be protected against local weather conditions. Outdoor air exhaust and intake openings shall meet the provisions for exterior wall opening protectives in accordance with this code.
R325.6 Interior stairway illumination. Interior stairways shall be provided with an artificial light source to illuminate the landings and treads. The light source shall be capable of illuminating treads and landings to levels of not less than 1 footcandle (11 lux) as measured at the center of treads and landings. There shall be a wall switch at each floor level to control the light source where the stairway has six or more risers.
Exception: A switch is not required where remote, central or automatic control of lighting is provided.
R325.7 Exterior stairway illumination. Exterior stairways shall be provided with an artificial light source located at the top landing of the stairway. Exterior stairways providing access to a basement from the outdoor grade level shall be provided with an artificial light source located at the bottom landing of the stairway.
R325.8 Required heating. Where the winter design temperature in Table R301.2 is below 60°F (16°C), every dwelling unit shall be provided with heating facilities capable of maintaining a room temperature of not less than 68°F (20°C) at a point 3 feet (914 mm) above the floor and 2 feet (610 mm) from exterior walls in habitable rooms at the design temperature. The installation of one or more portable space heaters shall not be used to achieve compliance with this section.
Note: See Section R301.1.1.1 for limited-density owner-built rural dwellings.
R325.9 Passive solar energy collectors. When a passive solar energy collector is designed as a conditioned area it shall comply with the California Energy Code. Nonconditioned passive solar energy collectors are exempt from the California Energy Code.
SECTION R326—SANITATION
R326.1 Toilet facilities. Every dwelling unit shall be provided with a water closet, lavatory, and a bathtub or shower.
R326.2 Kitchen. Each dwelling unit shall be provided with a kitchen area and every kitchen area shall be provided with a sink.
R326.3 Sewage disposal. Plumbing fixtures shall be connected to a sanitary sewer or to an approved private sewage disposal system.
R326.4 Water supply to fixtures. Plumbing fixtures shall be connected to an approved water supply. Kitchen sinks, lavatories, bathtubs, showers, bidets, laundry tubs and washing machine outlets shall be provided with hot and cold water.
CMC § 1.4. High relevance — show source text
1.4. The penetrations are in parking garage exhaust or supply shafts that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction. 2. In Group B and R occupancies equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1, smoke dampers are not required at penetrations of shafts where all of the following criteria are met: 2.1. Kitchen, clothes dryer, bathroom and toilet room exhaust openings are installed with steel exhaust subducts, having a wall thickness of not less than 0.0187 inch (0.4712 mm). 2.2. The subducts extend not less than 22 inches (559 mm) vertically. 2.3. An exhaust fan is installed at the upper terminus of the shaft that is powered continuously in accordance with the provisions of Section 909.11, so as to maintain a continuous upward airflow to the outdoors. 3. Smoke dampers are not required at penetration of exhaust or supply shafts in parking garages that are separated from other building shafts by not less than 2-hour fire-resistance-rated construction. 4. Smoke dampers are not required at penetrations of shafts where ducts are used as part of an approved mechanical smoke control system designed in accordance with Section 909 and where the smoke damper will interfere with the operation of the smoke control system. 5. Fire dampers and combination fire/smoke dampers are not required in kitchen and clothes dryer exhaust systems where dampers are prohibited by the California Mechanical Code .
717.5.3.1 Continuous upward airflow. Fire dampers and smoke dampers shall not be installed in shafts that are required to maintain a continuous upward airflow path where closure of the damper would result in the loss of the airflow.
717.5.4 Fire partitions. In other than Group A, E, I and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, ducts and air transfer openings that penetrate fire partitions shall be protected with listed fire dampers installed in accordance with their listing.
Exceptions: In occupancies other than Group H and L, fire dampers are not required where any of the following apply:
- Corridor walls in buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 and the duct is protected as a through penetration in accordance with Section 714.
- Tenant partitions in covered and open mall buildings where the walls are not required by provisions elsewhere in the code to extend to the underside of the floor or roof sheathing, slab or deck above.
- The duct system is constructed of approved materials in accordance with the California Mechanical Code and the duct penetrating the wall complies with all of the following requirements: 3.1. The duct shall not exceed 100 square inches (0.06 m [2] ). 3.2. The duct shall be constructed of steel not less than 0.0217 inch (0.55 mm) in thickness.
3.3. The duct shall not have openings that communicate the corridor with adjacent spaces or rooms. 3.4. The duct shall be installed above a ceiling. 3.5. The duct shall not terminate at a wall register in the fire-resistance-rated wall. 3.6. A minimum 12-inch-long (305 mm) by 0.060-inch-thick (1.52 mm) steel sleeve shall be centered in each duct opening.
CMC § 62.1. High relevance — show source text
(3) The mechanical exhaust flow minus the available transfer air from conditioned spaces or return air plenums on the same floor, not in different smoke or fire compartments, and that at their closest point are within 15 feet (4572 mm) of each other. Available transfer air is that portion of outdoor ventilation air that:
(a) is not required to satisfy other exhaust needs,
(b) is not required to maintain pressurization of other spaces, and
(c) is transferable according to applicable codes and standards and to the class of air recirculation limitations in Chapter 4 or ASHRAE 62.1.
Exceptions: (1) Biosafety level classified laboratories 3 or higher. (2) Vivarium spaces. (3) Spaces that are required by applicable codes and standards to be maintained at positive pressure relative to adjacent spaces. For spaces taking this exception, any transferable air that is not directly transferred shall be made available to the associated air-handling unit and shall be used whenever economizer or other options do not save more energy. (4) Spaces where the demand for transfer air may exceed the available transfer airflow rate and where the spaces have a required negative pressure relationship. For spaces taking this exception, any transferable air that is not directly transferred shall be made available to the associated air-handling unit and shall be used whenever economizer or other options do not save more energy. [ASHRAE 90.1:6.5.7.1] E 503.5.11.2 Kitchen Exhaust Systems. Replacement air introduced directly into the hood cavity of kitchen exhaust hoods shall not exceed 10 percent of the hood exhaust airflow rate. [ASHRAE 90.1:6.5.7.2.1]
E 503.5.11.2.1 Exhaust Flow Rate. Where a kitchen or dining facility has a total kitchen hood exhaust airflow rate exceeding 5000 ft [3] /min (2.3597 m [3] /s), each hood shall have an exhaust rate in accordance with Table E 503.5.11.2.1.
Where a single hood, or hood section, is installed over appliances with different duty ratings, the maximum allowable flow rate for the hood or
hood section shall not exceed the values in Table E 503.5.11.2.1 for the highest appliance duty rating under the hood or hood section. Refer to ASHRAE 154 for definitions of hood type, appliance duty, and net exhaust flow rate. Exception: Seventy-five percent or more of the total replacement air is transfer air that would otherwise be exhausted. [ASHRAE 90.1:6.5.7.2.2] E 503.5.11.2.2 Kitchen or Dining Facility. Where a kitchen or dining facility has a total kitchen hood exhaust airflow rate more than 5000 ft [3] /min (2.3597 m [3] /s), then one of the following shall be provided:
(1) Fifty percent or more of all replacement air is transfer air that would otherwise be
exhausted.
(2) Demand ventilation systems on 75 percent or more of the exhaust air. Such systems shall be capable of and configured to provide 50 percent or more reduction in exhaust and replacement air system airflow rates, including controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent, and combustion products during cooking and idle.
CMC § 1.9 High relevance — show source text
Natural ventilation shall not be required in kitchens where a local exhaust system is installed in accordance with the California Mechanical Code .
Required ventilation openings shall be permitted to open into a thermally isolated sunroom or roofed porch, deck, or patio where not less than 40 percent of the roofed area perimeter is open to the outdoor air.
Required ventilation openings shall be permitted to open into a thermally isolated sunroom provided there is an openable area between the adjoining room and the sunroom of not less than one-tenth of the floor area of the interior room and not less than 20 square feet (1.9 m [2] ). The minimum openable area of the sunroom to outdoor air shall be based on the total floor area of the adjoining room and the sunroom. 5. The windows, doors, louvers and other approved closeable openings not required by Section R319 may open into a passive solar energy collector for ventilation required by this section. The area of ventilation openings to the outside of the passive solar energy collector shall be increased to compensate for the openings required by the interior space.
R325.1.3 Adjoining rooms. For the purpose of determining light and ventilation requirements, rooms shall be considered to be a portion of an adjoining room where not less than one-half of the area of the common wall is open and unobstructed and provides an opening of not less than one-tenth of the floor area of the interior room and not less than 25 square feet (2.3 m [2] ).
R325.2 Bathrooms. Bathrooms, water closet compartments and other similar rooms shall be provided with aggregate glazing area in windows of not less than 3 square feet (0.3 m [2] ), one-half of which shall be openable.
Exception: The glazed areas shall not be required where artificial light and a local exhaust system are provided. The minimum local exhaust rates shall be 50 cubic feet per minute (25 L/s) for intermittent ventilation or 20 cubic feet per minute (10 L/s) for contin- uous ventilation in accordance with the California Mechanical Code, Chapter 4 . Exhaust air from the space shall be exhausted directly to the outdoors.
R325.2.1 Bathroom exhaust fans. Each bathroom containing a bathtub, shower or tub/shower combination shall be mechanically ventilated for purposes of humidity control in accordance with the California Mechanical Code, Chapter 4; and the California Green Building Standards Code, Chapter 4, Division 4.5.
Note: Window operation is not a permissible method of providing bathroom exhaust for humidity control.
3-72 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
BUILDING PLANNING
R325.3 Ventilation. Ventilation air rates shall be in compliance with the California Mechanical Code.
R325.4 Opening location. Outdoor intake and exhaust openings shall be located in accordance with Sections R325.4.1 and R325.4.2.
R325.4.1 Intake openings. Mechanical and gravity outdoor air intake openings shall be located not less than 10 feet (3048 mm) from any hazardous or noxious contaminant, such as vents, chimneys, plumbing vents, streets, alleys, parking lots and loading docks.
For the purpose of this section, the exhaust from dwelling unit toilet rooms, bathrooms and kitchens shall not be considered as hazardous or noxious.
CMC § 4-1 High relevance — show source text
CHAPTER 4 SPECIAL DETAILED REQUIREMENTS
BASED ON OCCUPANCY AND USE . . . . . . . . . . . . . . . . . . . .4-1
401 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
402 Covered Mall and Open Mall Buildings . . . . . . . . . . . . 4-5
403 High-Rise Buildings and Group I-2 Occupancies Having Occupied Floors Located More Than 75 Feet above the Lowest Level of
Fire Department Vehicle Access . . . . . . . . . . . . . . . 4-9
404 Atriums. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
405 Underground Buildings . . . . . . . . . . . . . . . . . . . . . . . . 4-13
406 Motor-Vehicle-Related Occupancies. . . . . . . . . . . . . 4-15
407 Group I-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
408 Group I-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
409 Motion Picture Projection Rooms . . . . . . . . . . . . . . . 4-30
410 Stages, Platforms and Technical Production Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-31
411 Special Amusement Areas . . . . . . . . . . . . . . . . . . . . . . 4-32
412 Aircraft-Related Occupancies . . . . . . . . . . . . . . . . . . . 4-33
413 Combustible Storage . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37
414 Hazardous Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37
415 Groups H-1, H-2, H-3, H-4 and H-5 . . . . . . . . . . . . . . . 4-42
416 Spray Application of Flammable Finishes . . . . . . . . 4-51
417 Drying Rooms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-52
418 Organic Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-52
419 Artificial Decorative Vegetation . . . . . . . . . . . . . . . . . 4-52
CMC § 3-5 High relevance — show source text
304 Business Group B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
305 Educational Group E . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
306 Factory Group F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
307 High-Hazard Group H . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
308 Institutional Group I . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
309 Mercantile Group M. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
310 Residential Group R. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15
311 Storage Group S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17
312 Utility and Miscellaneous Group U . . . . . . . . . . . . . . 3-18
313 Laboratories Group L [SFM]. . . . . . . . . . . . . . . . . . . . . . .3-19
314 Organized Camps Group C [SFM]. . . . . . . . . . . . . . . . . .3-19
CHAPTER 4 SPECIAL DETAILED REQUIREMENTS
BASED ON OCCUPANCY AND USE . . . . . . . . . . . . . . . . . . . .4-1
401 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
402 Covered Mall and Open Mall Buildings . . . . . . . . . . . . 4-5
403 High-Rise Buildings and Group I-2 Occupancies Having Occupied Floors Located More Than 75 Feet above the Lowest Level of
Fire Department Vehicle Access . . . . . . . . . . . . . . . 4-9
404 Atriums. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
405 Underground Buildings . . . . . . . . . . . . . . . . . . . . . . . . 4-13
406 Motor-Vehicle-Related Occupancies. . . . . . . . . . . . . 4-15
407 Group I-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
408 Group I-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
CMC § 405.6 Medium relevance — show source text
Umbrella Structure 3103 Underground Buildings 405 Alarms and detection 405.6
Compartmentation 405.4 Construction type 405.2 Elevators 405.4.3 Emergency power loads 405.8, 2702.2 Means of egress 405.7 Smoke barrier 405.4.2, 405.4.3 Smoke exhaust/control 405.5 Smokeproof enclosure 405.7.2, 1023.12 Sprinkler protection 405.3 Standby power 405.8, 2702.2 Standpipe system 405.9 Underlayment 1507.1.1, 1507.2.3, 1507.3.3, 1507.4.5, 1507.5.3, 1507.6.3, 1507.7.3, 1507.8.3, Table 1507.8, 1507.9.3, 1507.16.3,
1507.17.3
Application 1507.1.1, 1507.3.3, 1507.17.4
Ice barrier 1507.1.2, 1507.2.7, 1507.5.4, 1507.6.4, 1507.7.4, 1507.8.4, 1507.9.4, 1507.16.4 Underpinning 1804.2
2025 CALIFORNIA BUILDING CODE INDEX-21
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
INDEX
Stone 1404.8, 1411 Terra cotta 1404.10, 1411 Vinyl 1404.15, 1411 Wood 1404.6, 1411 Ventilation (see Mechanical) 101.4.2 Aircraft paint hangars 412.5.6 Attic 1202.2, 1503.4 Bathrooms 1202.5.2.1 California Energy Code and International Energy Conservation Code Climate Zones 1202.3.1, Table 1202.3.1 Crawl space 1202.4 Exhaust, hazardous 1202.6 Exhaust, HPM 415.11.1.6 Hazardous 414.3, 415.11.1.6, 415.11.1.8.1, 415.11.11.1, 415.11.11.2, 415.11.3.2, 415.11.6.4, 415.11.6.8, 415.11.7.4, 415.9.1.7 High-rise stairways 1023.11 HPM service corridors 415.11.3.2
Live/work unit 508.5.10 Mechanical 1202.1
Natural 1202.5 Parking 406.5.10, 406.5.2, 406.5.5, 406.6.2
Projection rooms 409.3 Repair garages 406.8.1 Roof 1202.2
CMC § 4.19 Medium relevance — show source text
See California Mechanical Code_
Table 4-A and ASHRAE 170 for ventilation requirements. See California Electrical Code, Article 517 for lighting and power requirements. See California Building Code Table
1224.4.19 for noise transmission requirements.
3. “Invasive procedure” is defined in Section 1224.3 definitions.|1. This table includes a brief description of the services performed in these room types and a summary of some applicable requirements that appear elsewhere in the California
Building Code.
2. Other requirements that apply to these room types include, but are not limited to, ventilation, lighting and sound transmission requirements. See California Mechanical Code
Table 4-A and ASHRAE 170 for ventilation requirements. See California Electrical Code, Article 517 for lighting and power requirements. See California Building Code Table
1224.4.19 for noise transmission requirements.
3. “Invasive procedure” is defined in Section 1224.3 definitions.|1. This table includes a brief description of the services performed in these room types and a summary of some applicable requirements that appear elsewhere in the California
Building Code.
2. Other requirements that apply to these room types include, but are not limited to, ventilation, lighting and sound transmission requirements. See California Mechanical Code
Table 4-A and ASHRAE 170 for ventilation requirements. See California Electrical Code, Article 517 for lighting and power requirements. See California Building Code Table
1224.4.19 for noise transmission requirements.
3. “Invasive procedure” is defined in Section 1224.3 definitions.|1. This table includes a brief description of the services performed in these room types and a summary of some applicable requirements that appear elsewhere in the California
Building Code.
2. Other requirements that apply to these room types include, but are not limited to, ventilation, lighting and sound transmission requirements. See California Mechanical Code
Table 4-A and ASHRAE 170 for ventilation requirements. See California Electrical Code, Article 517 for lighting and power requirements. See California Building Code Table
1224.4.19 for noise transmission requirements.
3. “Invasive procedure” is defined in Section 1224.3 definitions.|1224.4.11.1.1 Coved base. Resilient flooring, if used in toilet and bathing rooms, shall be continuous and extend upward onto the wall at least 5 inches (127 mm) to minimize moisture infiltration. Wood bases are prohibited except in waiting areas and administration departments.
1224.4.11.1.2 Food preparation areas. Floors in areas used for food preparation and assembly shall be water-resistant. Floor surfaces, including tile joints, shall be resistant to food acids. Floor construction in dietary and food preparation areas shall be free of spaces that can harbor pests.
1224.4.11.1.3 Wet cleaning. In all areas subject to frequent wet-cleaning methods, flooring materials shall not be physically affected by germicidal or other types of cleaning solutions.
1224.4.11.1.4 Airborne infection isolation, airborne infection isolation exam/treatment and protective environment rooms. These rooms and anterooms shall have seamless flooring with integral coved base.
1224.4.11.2 Wall bases.
CMC § 8-1 Medium relevance — show source text
CONTENTS
CHAPTER 8-1 ADMINISTRATION . . . . . . . . . . . . . . . . . . . . . . . 1
Section
8-101 Title, Purpose and Intent. . . . . . . . . . . . . . . . . . . . . . . . . 1 8-102 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8-103 Organization and Enforcement . . . . . . . . . . . . . . . . . . . 1 8-104 Review and Appeals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 8-105 Construction Methods and Materials . . . . . . . . . . . . . . 2
8-106 SHBSB Rulings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
CHAPTER 8-2 DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Section
8-201 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
CHAPTER 8-3 USE AND OCCUPANCY . . . . . . . . . . . . . . . . . . . 5
Section
8-301 Purpose and Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8-302 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8-303 Residential Occupancies. . . . . . . . . . . . . . . . . . . . . . . . . 5
CHAPTER 8-4 FIRE PROTECTION. . . . . . . . . . . . . . . . . . . . . . . 7
Section
8-401 Purpose, Intent and Scope . . . . . . . . . . . . . . . . . . . . . . . 7
8-402 Fire-resistive Construction . . . . . . . . . . . . . . . . . . . . . . . 7
8-403 Interior Finish Materials. . . . . . . . . . . . . . . . . . . . . . . . . . 7
8-404 Wood Lath and Plaster. . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8-405 Occupancy Separation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8-406 Maximum Floor Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
CMC § 605.7.6 Medium relevance — show source text
605.7.6 Flue-fed incinerators in Group I-2. In Group I-2 occupancies, the continued use of existing flue-fed incinerators is prohibited.
605.7.7 Incinerator inspections in Group I-2. Incinerators in Group I-2 occupancies shall be inspected not less than annually in accordance with the manufacturer’s instructions. Inspection records shall be maintained on the premises and made available to the fire code official upon request.
605.8 Gas meters. Above-ground gas meters, regulators and piping subject to damage shall be protected by a barrier complying with Section 312 or otherwise protected in an approved manner.
SECTION 606—COMMERCIAL COOKING EQUIPMENT AND SYSTEMS
[M] 606.1 General. Commercial kitchen exhaust hoods shall comply with the requirements of the California Mechanical Code .
[M] 606.2 Where required. A Type I hood shall be installed at or above all commercial cooking appliances and domestic cooking appliances used for commercial purposes that produce grease vapors.
Exceptions:
Factory-built commercial exhaust hoods that are listed and labeled in accordance with UL 710, and installed in accordance with Section 304.1 of the California Mechanical Code, shall not be required to comply with Sections 507.1.5, 507.2.3, 507.2.5, 507.2.8, 507.3.1, 507.3.3, 507.1.6 and 507.2.10 of the California Mechanical Code .
Factory-built commercial cooking recirculating systems that are listed and labeled in accordance with UL 710B, and installed in accordance with Section 304.1 of the California Mechanical Code, shall not be required to comply with Sections 507.1.5, 507.2.3, 507.2.5, 507.2.8, 507.3.1, 507.3.3, 507.1.6 and 507.2.10 of the California Mechanical Code . Spaces in which such systems are located shall be considered to be kitchens and shall be ventilated in accordance with Table 403.3.1.1 of the California Mechanical Code . For the purpose of determining the floor area required to be ventilated, each individual appliance shall be considered as occupying not less than 100 square feet (9.3 m [2] ).
Where cooking appliances are equipped with integral down-draft exhaust systems and such appliances and exhaust systems are listed and labeled for the application in accordance with NFPA 96, a hood shall not be required at or above them.
A Type I hood shall not be required for an electric cooking appliance where an approved testing agency provides documentation that the appliance effluent contains 5 mg/m [3] or less of grease when tested at an exhaust flow rate of 500 cfm (0.236 m [3] /s) in accordance with UL 710B.
606.3 Operations and maintenance. Commercial cooking systems shall be operated, inspected and maintained in accordance with Sections 606.3.1 through 606.3.4.
606.3.1 Ventilation system. The ventilation system in connection with hoods shall be operated at the required rate of air movement, and grease filters listed and labeled in accordance with UL 1046 shall be in place where equipment under a kitchen grease hood is used.
CMC § 1202.5.2 Medium relevance — show source text
1202.5.2 Contaminants exhausted. Contaminant sources in naturally ventilated spaces shall be removed in accordance with the California Mechanical Code and the California Fire Code .
1202.5.2.1 Bathrooms. Rooms containing bathtubs, showers, spas and similar bathing fixtures shall be mechanically ventilated in accordance with the California Mechanical Code .
The minimum exhaust rate shall not be less than that established by Table 403.7 “Minimum Exhaust Rates.” See California Mechanical Code, Chapter 5, for additional provisions related to environmental air ducts.
[HCD 1] In addition to the requirements in this section and in the California Mechanical Code, bathrooms in Group R occupancies shall be mechanically ventilated in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.5.
1202.5.3 Openings on yards or courts. Where natural ventilation is to be provided by openings onto yards or courts, such yards or courts shall comply with Section 1205.
1202.6 Other ventilation and exhaust systems. Ventilation and exhaust systems for occupancies and operations involving flammable or combustible hazards or other contaminant sources as covered in the California Mechanical Code or the California Fire Code shall be provided as required by both codes.
SECTION 1203—TEMPERATURE CONTROL
1203.1 Equipment and systems. Interior spaces intended for human occupancy shall be provided with active or passive space heating systems capable of maintaining an indoor temperature of not less than 68°F (20°C) at a point 3 feet (914 mm) above the floor on the design heating day.
Exceptions: 1. Space heating systems are not required for: 1.1. Interior spaces where the primary purpose of the space is not associated with human comfort.
1.2. Group F, H, S or U occupancies. 2. [HCD 1] For limited-density owner-built rural dwellings, a heating facility or appliance shall be installed in each dwelling subject to the provisions of Subchapter 1, Chapter 1, Title 25, California Code of Regulations, commencing with Section 74; however, there shall be no specified requirement for heating capacity or temperature maintenance. The use of solid-fuel or solar-heating devices shall be deemed as complying with the requirements of this section. If nonrenewable fuel is used in these dwellings, rooms so heated shall meet current installation standards. 3. [OSHPD 1, 1R, 2, 3, 4 & 5] Space heating systems shall comply with the requirements of the California Mechanical Code. 4. [HCD 1] When a passive solar energy collector is designed as a conditioned area it shall comply with the California Energy Code. Nonconditioned passive solar energy collectors are exempt from compliance with the California Energy Code.
12-6 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
INTERIOR ENVIRONMENT
SECTION 1204—LIGHTING
1204.1 General. Every space intended for human occupancy shall be provided with natural light by means of exterior glazed openings in accordance with Section 1204.2 or shall be provided with artificial light in accordance with Section 1204.3. Exterior glazed openings shall open directly onto a public way or onto a yard or court in accordance with Section 1205.
CMC § 1202.5.1 Medium relevance — show source text
agency.
[HCD 1] The windows, doors, louvers or other approved closeable openings not required by Section 1030 may open into a passive solar energy collector for ventilation required by this section. The area of ventilation openings to the outside of the passive solar energy collec- tor shall be increased to compensate for the openings required by the interior space.
1202.5.1 Ventilation area required. The openable area of the openings to the outdoors shall be not less than 4 percent of the floor area being ventilated.
1202.5.1.1 Adjoining spaces. Where rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall be unobstructed and shall have an area of not less than 8 percent of the floor area of the interior room or space, but not less than 25 square feet (2.3 m [2] ). The openable area of the openings to the outdoors shall be based on the total floor area being ventilated.
Exception: Exterior openings required for ventilation shall be allowed to open into a sunroom with thermal isolation or a patio cover provided that the openable area between the sunroom addition or patio cover and the interior room shall have 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 m [2] ). The openable area of the openings to the outdoors shall be based on the total floor area being ventilated.
1202.5.1.2 Openings below grade. 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.
1202.5.2 Contaminants exhausted. Contaminant sources in naturally ventilated spaces shall be removed in accordance with the California Mechanical Code and the California Fire Code .
1202.5.2.1 Bathrooms. Rooms containing bathtubs, showers, spas and similar bathing fixtures shall be mechanically ventilated in accordance with the California Mechanical Code .
The minimum exhaust rate shall not be less than that established by Table 403.7 “Minimum Exhaust Rates.” See California Mechanical Code, Chapter 5, for additional provisions related to environmental air ducts.
[HCD 1] In addition to the requirements in this section and in the California Mechanical Code, bathrooms in Group R occupancies shall be mechanically ventilated in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.5.
1202.5.3 Openings on yards or courts. Where natural ventilation is to be provided by openings onto yards or courts, such yards or courts shall comply with Section 1205.
1202.6 Other ventilation and exhaust systems. Ventilation and exhaust systems for occupancies and operations involving flammable or combustible hazards or other contaminant sources as covered in the California Mechanical Code or the California Fire Code shall be provided as required by both codes.
SECTION 1203—TEMPERATURE CONTROL
1203.1 Equipment and systems. Interior spaces intended for human occupancy shall be provided with active or passive space heating systems capable of maintaining an indoor temperature of not less than 68°F (20°C) at a point 3 feet (914 mm) above the floor on the design heating day.
CMC § 8-301 Medium relevance — show source text
Section
8-301 Purpose and Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8-302 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8-303 Residential Occupancies. . . . . . . . . . . . . . . . . . . . . . . . . 5
CHAPTER 8-4 FIRE PROTECTION. . . . . . . . . . . . . . . . . . . . . . . 7
Section
8-401 Purpose, Intent and Scope . . . . . . . . . . . . . . . . . . . . . . . 7
8-402 Fire-resistive Construction . . . . . . . . . . . . . . . . . . . . . . . 7
8-403 Interior Finish Materials. . . . . . . . . . . . . . . . . . . . . . . . . . 7
8-404 Wood Lath and Plaster. . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8-405 Occupancy Separation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8-406 Maximum Floor Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8-407 Vertical Shafts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8-408 Roof Covering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8-409 Fire Alarm Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8-410 Automatic Sprinkler Systems. . . . . . . . . . . . . . . . . . . . . 8 8-411 Other Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8-412 High-rise Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
CHAPTER 8-5 MEANS OF EGRESS . . . . . . . . . . . . . . . . . . . . . . 9
Section
8-501 Purpose, Intent and Scope . . . . . . . . . . . . . . . . . . . . . . . 9 8-502 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8-503 Escape or Rescue Windows and Doors. . . . . . . . . . . . 10 8-504 Railings and Guardrails . . . . . . . . . . . . . . . . . . . . . . . . . 10
CMC § 25.4 Medium relevance — show source text
7 or No.
67)|30|2|2|2|13|15|17|21|25|30|14|17|19|22|24|27|32|37|42| |ASTM D1863
(No. 7 or No.
67)|50|12|12|14|16|18|21|25|30|35|17|19|22|25|28|30|36|41|47| |ASTM D1863
(No. 7 or No.
67)|100|14|16|19|21|24|27|32|37|42|21|24|26|29|32|35|41|47|53| |ASTM D1863
(No. 7 or No.
67)|150|17|19|22|25|27|30|36|41|46|23|26|29|32|35|38|44|50|56| |ASTM D1863
(No. 6)|15|2|2|2|2|12|12|12|15|18|2|2|2|13|15|17|22|26|30| |ASTM D1863
(No. 6)|20|2|2|2|2|12|12|13|17|21|2|2|12|15|17|19|23|28|32| |ASTM D1863
(No. 6)|30|2|2|2|2|12|12|16|20|24|2|12|14|17|19|21|26|31|35| |ASTM D1863
(No. 6)|50|12|12|12|12|14|16|20|24|28|12|15|17|19|22|24|29|34|39| |ASTM D1863
(No. 6)|100|12|12|14|16|19|21|26|30|35|16|18|21|24|26|29|34|39|45| |ASTM D1863
(No. 6)|150|12|14|17|19|22|24|29|34|39|18|21|23|26|29|32|37|43|48| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.
a. Parapet height is measured vertically from the top surface of the coping down to the surface of the roof covering in the field of the roof adjacent to the parapet and outbound
of any cant strip.
b. Interpolation shall be permitted for wind speed, mean roof height and parapet height. Extrapolation is not permitted.
c. Basic wind speed,V, and wind exposure shall be determined in accordance with Section 1609.
d. Where the minimum required parapet height is indicated to be 2 inches (51 mm), a gravel stop shall be permitted and shall extend not less than 2 inches (51 mm) from the roof
surface and not less than the height of the aggregate.
e. The tabulated values apply only to conditions where the topographic factor (Kzt) determined in accordance with Chapter 26 of ASCE 7 is 1.0 or where_Kzt_ is incorporated in the
basic wind speed in Section 1609.
f.CMC § 501.3 Medium relevance — show source text
501.3, 504.3, 504.3.1, 504.5, 504.7, 504.7.1
E136— 2024a : Standard Test Method for Assessing Combustibility of Materials Using a Vertical Tube Furnace at 750 Degrees C
501.4.1
E1354— 2023 : Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter
503.2.4.3.2, 503.2.4.3.3
E2632—2020: Standard Test Method for Evaluating the Under-Deck Fire Test Response of Deck Materials
504.7.3.2, 504.7.3.3, 504.7.3.3.1, 504.7.3.4
E2652—2022: Standard Test Method for Assessing Combustibility of Materials Using a Tube Furnace with a Cone-shaped Airflow Stabilizer, at 750°C
501.4.1
E2707—2022: Standard Test Method for Determining Fire Penetration of Exterior Wall Assemblies Using a Direct Flame Impingement Exposure
504.5, 504.9, 504.9.3
E2726/E2726M—2012a(2017): Standard Test Method for Evaluating the Fire Test Response of Deck Structures to Burning Brands
504.7.3.2, 504.7.3.3, 504.7.3.3.2
E2768—11(2018): Standard Test Method for Extended Duration Surface Burning Characteristics of Building Materials (30 min Tunnel Test)
503.2.4
2025 CALIFORNIA WILDLAND-URBAN INTERFACE CODE 7-3
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
REFERENCED STANDARDS
E2886/E2886M—20: Standard Test Method for Evaluating the Ability of Exterior Vents to Resist the Entry of Embers and Direct Flame Impingement
504.10.1
E2957—2017 : Standard Test Method for Resistance to Wildfire Penetration of Eaves, Soffits and Other Projections
504.3, 504.7, 504.7.1, 504.7.2
G155—2021: Standard Practice for Operating Xenon Arc Lamp Apparatus for Exposure of Materials
504.9.2
ICC International Code Council, Inc., 200 Massachusetts Avenue, NW, Suite 250, Washington, DC 20001
CBC—2025: California Building Code
CMC § 150.0 Medium relevance — show source text
For this scenario, 4 in. (100 mm) oval duct shall be permitted, provided the minor axis of the oval is greater than or equal to 3 in. (75 mm)
f. When a vented range hood utilizes a capture efficiency rating to demonstrate compliance with 150.0(o)1Giiib, a static pressure greater than or equal to 0.25 in. of water at the
rating point shall not be required, and the airflow listed in the approved directory corresponding to the compliant capture efficiency rating point shall be applied to Table
150.0-H for determining compliance.|vi. Sound ratings for local mechanical exhaust. Local mechanical exhaust systems shall be rated for sound in accordance with Section 7.2 of ASHRAE 62.2 at no less than the minimum airflow rate required by Section 150.0(o)1G. Exception to Section 150.0(o)1Gvi: Kitchen range hoods may be rated for sound at no less than 100 cfm at a static pressure determined at working speed as specified in HVI 916 section 7.2. H. Airflow measurement of whole-dwelling unit ventilation. The airflow required by Section 150.0(o)1C is the quantity of outdoor ventilation air supplied or indoor air exhausted by the mechanical ventilation system as installed and shall be measured by using a flow hood, flow grid or other airflow measuring device at the mechanical ventilation fan’s inlet terminals/grilles or outlet terminals/grilles in accordance with the procedures in Reference Residential Appendix RA3.7. Balanced mechanical ventilation system airflow shall be the average of the supply fan and exhaust fan flows.
2025 CALIFORNIA ENERGY CODE 173
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SINGLE-FAMILY RESIDENTIAL BUILDINGS— MANDATORY FEATURES AND DEVICES
I. Sound ratings for whole-dwelling unit ventilation systems. Whole-dwelling unit ventilation systems shall be rated for sound in accordance with Section 7.3 of ASHRAE 62.2 at no less than the minimum airflow rate required by Section 150.0(o)1C.
J. Label for whole-dwelling unit ventilation system on-off control. Compliance with ASHRAE 62.2 Section 4.4 (Control and Operation) shall require manual ON-OFF control switches associated with whole-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 switch in the ‘on’ position at all times unless the outdoor air quality is very poor.” K. Combustion air and compensating outdoor air or makeup air. i. All dwelling units shall conform to the applicable requirements specified in California Mechanical Code Chapter 7, Combustion Air. ii. All dwelling units shall conform to the requirements in ASHRAE 62.2 Section 6.4, Combustion and Solid-FuelBurning Appliances. 2. Field verification and diagnostic testing. A. Whole-dwelling unit ventilation airflow performance. The whole-dwelling unit ventilation airflow required by Section 150.0(o)1C shall be confirmed through field verification and diagnostic testing in accordance with the applicable procedures specified in Reference Residential Appendix RA3.7. Balanced mechanical ventilation system airflow shall be the average of the supply fan and exhaust fan flows. Ventilation airflow of systems with multiple operating modes shall be tested in all modes designed to comply with the required ventilation airflows. B.
CMC § 1207.1.8 Medium relevance — show source text
Fire remediation 1207.1.8 Hazard mitigation analysis 1207.1.6 Large-scale fire test 1207.1.7 Mobile ESS 202, 1207.1, 1207.1.2,
1207.10 Residential (R-3 and R-4) 1207.11 Stationary ESS 202, 1207 Walk-in units 202, 1207.1.7, 1207.4.12, 1207.4.6, 1207.4.8, 1207.4.9, 1207.5.2, 1207.5.2.1, 1207.5.4, 1207.5.5, 1207.5.6, 1207.6.1, 1207.6.3, 1207.9.4 Energy Systems Chapter 12, 1201.1, 1201.2 Electrical energy storage systems 1201.3, 1207 Emergency and standby power systems 1203
Permits 105.5.14, 105.6.10, 105.6.21,
105.6.6 Portable generators 1204, 3309 Solar and photovoltaic systems 1205 Stationary fuel cell power systems 1206 Entry, Right of 104.4 Equipment, Fueled 313 Equipment Platform Defined 202
Guards required 1015.2 Escalator Openings (see Floor Openings and Shafts) Escape Openings 1031 ESFR Sprinklers (see Automatic Sprinklers) Ethylene Gas 2503
Generators 2506
Evacuation 115.2, 405, 2603.3.4, 2603.3.5 Evacuation Diagrams 403.9.1.1, 403.9.2.3 Evacuation Drills 405 Frequency 405.3, Table 405.3 Notification 405.7 Recall and reentry 405.10 Evacuation Plans 404
Excess Flow Control
Defined 202
Excess Flow Valve
Defined 202
Exhausted Enclosure 202, 5003.8.5 Exhibit Gallery Occupancy load Table 1004.5 Exhibition Halls (Occupancy Group A-3)
202
Exhibits and Trade Shows 105.5.15 Existing Defined 202 Existing Buildings Chapter 11 Group I-2 1105 Outdoor occupancies 1106 Exit 1022 Configuration 1007 Defined 202
Enclosure 1023
Horizontal 1026 Number required 1006 Passageways 1024
Ramps, interior and exterior 1023, 1027 Stairways, interior or exterior 1023, 1027 Stories 1004.2.3, 1006.3, 1017.3.1 Exit Access 101, 1016, 1017, 1018, 1019 Aisles 1018
Atriums 1006.3.2, 1017.3.2, 1019.3 Balconies 1017.2.1, 1021 Common path 1006.2.1 Corridor 1020
Frequently asked questions
What is the minimum bathroom fan cfm required by the CMC?
The California Mechanical Code requires 50 ft³/min (23.6 L/s) for intermittent operation and 25 ft³/min (11.8 L/s) for continuous operation under §405.3.1.
Can I use a window instead of a bathroom exhaust fan?
No. Where the code requires mechanical exhaust for humidity control (bathrooms with tub/shower), window operation is not an acceptable substitute; see CMC §405.3 and the Residential Code (R325.2.1) cross‑reference.
Does the CMC specify kitchen exhaust cfm?
Not in §405.4. The CMC requires a mechanical exhaust discharging outdoors and accessible controls; numeric airflow/capture requirements for kitchen hoods are addressed in other codes/standards (Energy Code / ASHRAE).
Are recirculating kitchen hoods allowed?
Recirculating systems are an exception in §405.4 only if installed in accordance with §516.0 and the manufacturer’s instructions. Otherwise the hood must discharge outdoors.
Where can I find the rules about where the exhaust terminates (clearances, distance from intakes)?
Those details are addressed by ventilation‑opening/termination provisions (see §405.5). The full text of §405.5 was not included in the uploaded excerpts — obtain the full section from the adopted CMC or AHJ to verify termination clearances.
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