CFC · California Fire Code

What are the requirements for carbon monoxide alarms and detection systems?

If your building contains a CO source, a fuel‑burning forced‑air furnace, an attached private garage, or a vehicle used inside the structure, the California Fire Code requires carbon monoxide detectors: put them outside each sleeping area and on every occupiable level (add detectors where a furnace serves enclosed rooms), use detectors/systems listed per the code, and maintain them per NFPA 72.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Fire Code requires carbon monoxide (CO) detection where certain risk conditions exist (for example: a CO source, a CO‑producing forced‑air furnace, an attached private garage, or a vehicle used inside the building) — see § 915.1. Required detector/ alarm locations for dwelling and sleeping units are set out in § 915.2, and carbon monoxide detection systems (detectors tied to controls/annunciation) are an accepted alternative to standalone alarms when they meet the listing and notification requirements in § 915.5. Maintenance is required in accordance with NFPA 72 per § 915.6.

Install CO detection when the building contains a CO source, a CO‑producing forced‑air furnace, an attached private garage, or a vehicle used in the building — and place detectors outside sleeping areas and on every occupiable level of dwellings. (Plain English restatement of § 915.1 and § 915.2.)

Requirements in detail

High‑level triggers (when detection is required)

  • If the building contains a CO source, detection is required. § 915.1.1.
  • If the building contains or is served by a CO‑producing forced‑air furnace, detection is required. § 915.1.1.
  • If the building has an attached private garage, detection is required. § 915.1.1.
  • If the building has a CO‑producing vehicle used inside the building, detection is required. § 915.1.1.

Where detectors / alarms must be located

  • Dwelling units:
    • Outside of each separate sleeping area in the immediate vicinity of the bedrooms. § 915.2.1(1).
    • On every occupiable level of the dwelling unit, including basements. § 915.2.1(2).
    • If a CO source is located within a bedroom or its attached bathroom, install a detector inside the bedroom. § 915.2.1(3).
  • Sleeping units (non‑dwelling): CO detection shall be installed in sleeping units (with a limited exception for units not served by a CO source or CO‑producing forced‑air furnace). § 915.2.2.
  • Group E (schools/classrooms): Where classrooms include the trigger conditions identified in § 915.1.1, install a carbon monoxide system using CO detectors and automatically transmit alarm signals to an on‑site staffed location (exception when occupant load ≤ 30). § 915.2.3.
  • Enclosed rooms/spaces served by fuel‑burning forced‑air furnace: Install CO detection in those enclosed rooms/spaces (see § 915.2.4). § 915.2.4.
  • The code requires installation “in accordance with the manufacturer’s published instructions” for placement specifics. § 915.2.

Detector / system characteristics and listing

  • Carbon monoxide detectors used in detection systems must be listed to UL 2075. § 915.5.1.
  • Combination CO/smoke detectors are acceptable if they are listed to UL 268 and UL 2075 and meet other State Fire Marshal listing/approval requirements. § 915.5.3.
  • Activation of a CO detector in a detection system must annunciate at the control unit and initiate audible and visible alarm notification throughout the building (with a specified exception allowing limited zoning if transmission to an approved on‑site or off‑site location occurs). § 915.5.4.
  • Duct or plenum mounted detectors shall not be used as a substitute for required protection under Section 915. § 915.5.5.

Maintenance & replacement

  • Maintenance of CO alarms and CO detection systems must comply with NFPA 72; inoperable detectors or those producing end‑of‑life signals must be replaced. § 915.6.
  • For enclosed parking garages, CO and NO2 detectors installed per the Mechanical Code must be maintained per the manufacturer’s instructions and replaced when inoperable or indicating end‑of‑life. § 915.6.1.

Quick decision table (decision‑relevant dimensions)

Decision factor What the code requires Code Reference
Trigger: building contains a CO source Install CO detection in locations required by § 915.2 § 915.1.1
Trigger: CO‑producing forced‑air furnace Install detection; also install detectors in enclosed rooms/spaces served by the furnace § 915.1.1; § 915.2.4
Trigger: Attached private garage Install CO detection per locations in § 915.2 (dwelling/sleeping rules apply) § 915.1.1; § 915.2
Dwelling unit placement Outside each sleeping area; on every occupiable level; inside bedroom if CO source there § 915.2.1
Sleeping unit placement CO detection required (exception where unit has no CO source and not served by CO‑producing forced‑air furnace) § 915.2.2
System detectors listing Detectors for systems: UL 2075; combos: UL 268 & UL 2075 § 915.5.1, § 915.5.3
Notification requirement for systems Annunciate at control unit and initiate audible/visible notification building‑wide (limited zoning exception) § 915.5.4
Maintenance Maintain per NFPA 72; replace inoperable / end‑of‑life § 915.6

Note: Specific mounting heights, spacing, sensor sensitivity thresholds and periodic test intervals are not stated in these Sections; the code defers to the manufacturer’s instructions and referenced standards (see § 915.2 and § 915.6).

Exceptions & special cases

  • The code exempts Group S, F and U occupancies that are not normally occupied from CO detection requirements. § 915.1 (exception).
  • Group E (schools): automatic transmission of alarm signals to on‑site staffed location is required unless occupant load is 30 or less (exception in § 915.2.3).
  • Duct/plenum detectors cannot replace required area detectors (see § 915.5.5).
  • The code allows combination CO/smoke detectors if listed as required (see § 915.5.3).

If you need to rely on alternative power sources, note that other sections (e.g., fire‑alarm and alarm power rules) or NFPA 72 may provide additional flexibility — the sections above require listed detectors and refer installation/detail work to manufacturer instructions and referenced standards.

Common mistakes

  • Installing battery‑only residential CO alarms when the building wiring serves the unit and the alarm is required to be on building power (read the power‑source exceptions carefully). The power rules for alarms are addressed elsewhere in Chapter 9 and related sections.
  • Using a detector mounted in an air‑handling duct as the only protection for spaces — § 915.5.5 forbids that substitution.
  • Confusing where alarms are permitted vs where detectors/systems are required: § 915.3.1 limits alarms to dwelling and sleeping units and requires detectors where the code specifies detectors. (Install the correct device type for the occupancy and location.)
  • Omitting interconnection in multi‑alarm dwelling installations where required (interconnection and listing requirements are found in adjacent provisions). Check the interconnection and listing rules before installation.

Worked example — 2‑story house with attached garage and forced‑air furnace

Scenario: 2‑story single‑family dwelling with a basement, an attached private garage, and a fuel‑burning forced‑air furnace located in a separate mechanical room that serves the building.

Code application (grounded in the cited sections):

  • Triggers present: attached private garage and CO‑producing forced‑air furnace ⇒ CO detection required. § 915.1.1.
  • Dwelling placements required:
    • One detector outside the sleeping area in the immediate vicinity of bedrooms (typically outside the bedroom doors on the 2nd floor). § 915.2.1(1).
    • One detector on every occupiable level: basement, first floor, second floor = 3 detectors (covers "on every occupiable level"). § 915.2.1(2).
    • Additionally, because the furnace serves enclosed rooms/spaces, install CO detection in the furnace/mechanical room per § 915.2.4 = +1 detector.
  • Total minimum detectors (typical, not including any bedroom‑internal detectors if CO sources inside bedrooms): 1 (outside sleeping area) + 2 (first & second floor occupiable levels) + 1 (basement occupiable level) + 1 (furnace room) = 5 detectors. (If the “outside sleeping area” detector is on the second floor occupiable level, count carefully to avoid double counting; the required rule is both outside sleeping area and on every occupiable level.) § 915.2.1; § 915.2.4.
  • Use detectors listed to UL 2075 where a detection system is installed, and follow manufacturer placement instructions and NFPA 72 for maintenance/replacement. § 915.5.1, § 915.2, § 915.6.

Note: The exact count can vary with layout (a detector outside a grouped bedroom bank can cover multiple bedrooms), so follow the “outside of each separate sleeping area in the immediate vicinity” language and the manufacturer placement guidance. § 915.2.1.

Related provisions

  • § 915.3 — Device types and connection to fire alarm systems (limits alarms to dwelling/sleeping units; detectors vs alarms)
  • § 915.4 — Carbon monoxide alarms (power source, listing, interconnection) — see residential alarm listing and interconnection rules.
  • § 915.5 — Carbon monoxide detection systems (listing, locations, combination detectors, occupant notification).
  • § 915.6 — Maintenance; NFPA 72 reference and garage detector maintenance.
  • § 1103.9 — Carbon monoxide detection requirements for existing buildings and related exceptions.

Code references

Grounded in the retrieved California Fire Code — click a citation to read the verbatim passage:

  • CFC § 914.11.1 High relevance — show source text

    914.11.1 Automatic sprinkler systems. An automatic sprinkler system shall be provided for ambulatory care facilities in accordance with Section 903.2.2.1.

    914.11.2 Manual fire alarm systems. A manual fire alarm system shall be provided for ambulatory care facilities in accordance with Section 907.2.2.

    914.11.3 Fire alarm systems. An automatic smoke detection system shall be provided for ambulatory care facilities in accordance with Section 907.2.2.1.

    SECTION 915—CARBON MONOXIDE (CO) DETECTION

    915.1 General. Carbon monoxide (CO) detection shall be installed in new buildings in accordance with Section 915.1.1 through 915.7 . Carbon monoxide detection shall be installed in existing buildings in accordance with this section and Section 1103.9.

    Pursuant to Health and Safety Code Section 17926, carbon monoxide detection shall be installed in all existing Group R buildings as required in this section.

    Exception: Carbon monoxide detection is not required in Group S, Group F and Group U occupancies that are not normally occupied.

    915.1.1 Where required. Carbon monoxide detection shall be installed in the locations specified in Section 915.2 where any of the following conditions exist.

    1. In buildings that contain a CO source.
    2. In buildings that contain or are supplied by a CO-producing forced-air furnace.
    3. In buildings with attached private garages.
    4. In buildings that have a CO-producing vehicle that is used within the building.

    915.2 Locations. Carbon monoxide detection shall be installed in accordance with the manufacturer’s published instructions in the locations specified in Sections 915.2.1 through 915.2.3.

    915.2.1 Dwelling units. Carbon monoxide detection shall be installed in dwelling units in the following locations: 1. Outside of each separate sleeping area in the immediate vicinity of the bedrooms. 2. On every occupiable level of a dwelling unit, including basements. 3. Where a CO source is located within a bedroom or its attached bathroom, carbon monoxide detection shall be installed within the bedroom.

    915.2.2 Sleeping units. Carbon monoxide detection shall be installed in sleeping units.

    Exception: Carbon monoxide detection shall be allowed to be installed outside of each separate sleeping area in the immediate vicinity of the sleeping unit where the sleeping unit or its attached bathroom does not contain a CO source and is not served by a CO-producing forced-air furnace.

    915.2.3 Group E occupancies. A carbon monoxide system that uses carbon monoxide detectors shall be installed in Group E occupancies where classrooms include any of the conditions identified in Sections 915.1.2 through 915.1.6 . Alarm signals from carbon monoxide detectors shall be automatically transmitted to an on-site location that is staffed by school personnel.

    Exception: Carbon monoxide alarm signals shall not be required to be automatically transmitted to an on-site location that is staffed by school personnel in Group E occupancies with an occupant load of 30 or less.

    915.2.4 CO-producing forced-air furnace. Carbon monoxide detection complying with Item 2 of Section 915.1.1 shall be installed in all enclosed rooms and spaces served by a fuel-burning, forced-air furnace.

  • CFC § 915.4.4 High relevance — show source text

    915.4.4 Interconnection. Where more than one carbon monoxide alarm is required to be installed within a dwelling unit or within a sleeping unit in Group R occupancies, the alarms shall be interconnected in a manner that activation of one alarm shall activate all of the alarms in the individual unit.

    Exception : Interconnection is not required in existing buildings, built prior to January 1, 2011, under any of the following conditions: 1. Physical interconnection is not required where listed wireless alarms are installed and all alarms sound upon activation of one alarm.

    2. No construction is taking place. 3. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 4. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding or the addition or replacement of windows or doors, or the addition of a porch or deck. 5. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    915.5 Carbon monoxide detection systems. Carbon monoxide detection systems shall be an acceptable alternative to carbon monoxide alarms and shall comply with Sections 915.5.1 through 915.5.3.

    9-76 2025 CALIFORNIA FIRE CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    FIRE PROTECTION AND LIFE SAFETY SYSTEMS

    915.5.1 General. Carbon monoxide detectors shall be listed in accordance with UL 2075.

    915.5.2 Locations. Carbon monoxide detectors shall be installed in the locations specified in Section 915.2. These locations supersede the locations specified in NFPA 72.

    915.5.3 Combination detectors. Combination carbon monoxide/smoke detectors shall be an acceptable alternative to carbon monoxide detectors, provided that they are listed in accordance with UL 268 and UL 2075.

    Combination carbon monoxide/smoke alarms shall comply with Section 915, and all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    915.5.4 Occupant notification. Activation of a carbon monoxide detector shall annunciate at the control unit and shall initiate audible and visible alarm notification throughout the building.

    Exception: Occupant notification is permitted to be limited to the area where the carbon monoxide alarm signal originated and other signaling zones in accordance with the fire safety plan, provided that the alarm signal from an activated carbon monoxide detector is automatically transmitted to an approved on-site location or off-premises location.

    915.5.5 Duct detection. Carbon monoxide detectors placed in environmental air ducts or plenums shall not be used as a substitute for the required protection in Section 915.

    915.6 Maintenance. Carbon monoxide alarms and carbon monoxide detection systems shall be maintained in accordance with NFPA 72. Carbon monoxide alarms and carbon monoxide detectors that become inoperable or begin producing end-of-life signals shall be replaced.

  • CFC § 914.8.4 High relevance — show source text

    914.8.4 Finishing. The process of “doping,” involving the use of a volatile flammable solvent, or of painting shall be carried on in a separate detached building equipped with automatic fire-extinguishing equipment in accordance with Section 903.

    914.8.5 Residential aircraft hangar smoke alarms. Smoke alarms shall be provided within residential aircraft hangars in accordance with Section 907.2.21.

    914.8.6 Aircraft paint hangar fire suppression. Aircraft paint hangars shall be provided with fire suppression as required by NFPA 409.

    914.9 Application of flammable finishes. An automatic sprinkler system or fire-extinguishing system shall be provided in all spray rooms and spray booths, and shall be installed in accordance with Chapter 9.

    914.10 Drying rooms. Drying rooms designed for high-hazard materials and processes, including special occupancies as provided for in Chapter 4 of the California Building Code, shall be protected by an approved automatic fire-extinguishing system complying with the provisions of Chapter 9.

    914.11 Ambulatory care facilities. Occupancies classified as ambulatory care facilities shall comply with Sections 914.11.1 through 914.11.3.

    9-74 2025 CALIFORNIA FIRE CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    FIRE PROTECTION AND LIFE SAFETY SYSTEMS

    914.11.1 Automatic sprinkler systems. An automatic sprinkler system shall be provided for ambulatory care facilities in accordance with Section 903.2.2.1.

    914.11.2 Manual fire alarm systems. A manual fire alarm system shall be provided for ambulatory care facilities in accordance with Section 907.2.2.

    914.11.3 Fire alarm systems. An automatic smoke detection system shall be provided for ambulatory care facilities in accordance with Section 907.2.2.1.

    SECTION 915—CARBON MONOXIDE (CO) DETECTION

    915.1 General. Carbon monoxide (CO) detection shall be installed in new buildings in accordance with Section 915.1.1 through 915.7 . Carbon monoxide detection shall be installed in existing buildings in accordance with this section and Section 1103.9.

    Pursuant to Health and Safety Code Section 17926, carbon monoxide detection shall be installed in all existing Group R buildings as required in this section.

    Exception: Carbon monoxide detection is not required in Group S, Group F and Group U occupancies that are not normally occupied.

    915.1.1 Where required. Carbon monoxide detection shall be installed in the locations specified in Section 915.2 where any of the following conditions exist.

    1. In buildings that contain a CO source.
    2. In buildings that contain or are supplied by a CO-producing forced-air furnace.
    3. In buildings with attached private garages.
    4. In buildings that have a CO-producing vehicle that is used within the building.

    915.2 Locations. Carbon monoxide detection shall be installed in accordance with the manufacturer’s published instructions in the locations specified in Sections 915.2.1 through 915.2.3.

  • CFC § 9-57 High relevance — show source text

    which do_ not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    2025 CALIFORNIA BUILDING CODE 9-57

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    �

    �

    FIRE PROTECTION AND LIFE SAFETY SYSTEMS

    [F] 915.4.2 Listings. Residential Carbon monoxide alarms shall be listed in accordance with UL 2034.

    No person shall install, market, distribute, offer for sale, or sell any carbon monoxide device in the State of California unless the device and instructions have been approved and listed by the Office of the State Fire Marshal.

    [F] 915.4.3 Combination alarms. Combination carbon monoxide/smoke alarms shall be an acceptable alternative to carbon monoxide alarms. Combination carbon monoxide/smoke alarms shall be listed in accordance with UL 217 and UL 2034.

    Combination carbon monoxide/smoke alarms shall comply with Section 915, and all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    [F] 915.4.4 Interconnection. Where more than one carbon monoxide alarm is required to be installed within a dwelling unit or within a sleeping unit in Group R occupancies, the alarms shall be interconnected in a manner that activation of one alarm shall activate all of the alarms in the individual unit.

    Exception: Interconnection is not required in existing buildings, built prior to January 1, 2011, under any of the following conditions:

    1. Physical interconnection is not required where listed wireless alarms are installed and all alarms sound upon activation of one alarm.

    2. No construction is taking place. 3. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 4. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck. 5. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    [F] 915.5 Carbon monoxide detection systems. Carbon monoxide detection systems shall be an acceptable alternative to carbon monoxide alarms and shall comply with Sections 915.5.1 through 915.5.3.

    [F] 915.5.1 General. Carbon monoxide detectors shall be listed in accordance with UL 2075.

    [F] 915.5.2 Locations. Carbon monoxide detectors shall be installed in the locations specified in Section 915.2 or NFPA 72.

    [F] 915.5.3 Combination detectors. Combination carbon monoxide/smoke detectors shall be an acceptable alternative to carbon monoxide detectors, provided that they are listed in accordance with UL 268 and UL 2075.

    Combination carbon monoxide/smoke detectors shall comply with all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    [F] 915.5.4 Occupant notification. Activation of a carbon monoxide detector shall annunciate at the control unit and shall initiate audible and visible alarm notification throughout the building.

  • CFC § 304.3.3 High relevance — show source text

    304.3.3 Criteria for incidental and minor structural alteration, additions, or repairs of pre-1973 code buildings. [OSHPD 1R, 2, 4 & 5] Provisions of this section shall apply to hospital buildings which were originally designed to pre-1973 building codes, and had no major structural alterations, additions or repairs using 1973 California Building Standards Code or later editions with an OSHPD permit. 1. Nonstructural components. Component importance factor, I p , shall be permitted to be 1.0. Exception: Components required for life safety purposes after an earthquake, including emergency, standby or alternative power systems, mechanical smoke removal systems, fire protection sprinkler systems, fire alarm control panels and egress stairways shall have a component importance factor (I p ) of 1.5.

    SECTION 305—IN-SITU LOAD TESTS

    [BS] 305.1 General. Where used, in-situ load tests shall be conducted in accordance with Section 1708 of the California Building Code .

    SECTION 306—ACCESSIBILITY FOR EXISTING BUILDINGS

    [DSA-AC] Public buildings, public accommodations, commercial facilities and public housing regulated by the Division of the State Architect-Access Compliance in Title 24, Part 2, California Building Code, Chapter 1, Section 1.9.1 shall comply with Title 24, Part 2, California Building Code, Chapter 11B.

    [HCD 1-AC] Accessibility requirements for covered multifamily dwellings, as defined in Chapter 2 of the California Building Code, are promulgated under HCD authority and are located in Chapter 11A of the California Building Code.

    SECTION 307—SMOKE ALARMS

    307.1 Smoke alarms. Where an alteration, addition, change of occupancy or relocation of a building is made to an existing building or structure of a Group R and I-1 occupancy, the existing building shall be provided with smoke alarms in accordance with the California Fire Code or Section R310 of the California Residential Code .

    Exception: Work classified as Level 1 Alterations in accordance with Chapter 7.

    SECTION 308—CARBON MONOXIDE DETECTION

    308.1 Carbon monoxide detection. Where an addition, alteration, change of occupancy or relocation of a building is made to an existing building, the existing building shall be provided with carbon monoxide detection in accordance with the California Fire Code or Section R311 of the California Residential Code .

    3-6 2025 CALIFORNIA EXISTING BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    PROVISIONS FOR ALL COMPLIANCE METHODS

    308.2 Carbon monoxide alarms in existing portions of a building. [HCD 1 & HCD 2] Pursuant to Health and Safety Code Section 17926, carbon monoxide detection shall be provided in all existing Group R buildings, as required in Section 915 of the California Building Code or Section R315 of the California Residential Code, as applicable.

  • CFC § 914.1.2 High relevance — show source text

    [F] 914.1.2 Interior access to shaftways. Door or window openings to a hoistway or shaftway from the interior of the building shall be plainly marked with the word “SHAFTWAY” in red letters not less than 6 inches (152 mm) high on a white background. Such warning signs shall be placed so as to be readily discernible.

    Exception: Markings shall not be required on shaftway openings that are readily discernible as openings onto a shaftway by the construction or arrangement.

    [F] 914.2 Equipment room identification. Fire protection equipment shall be identified in an approved manner. Rooms containing controls for air-conditioning systems, sprinkler risers and valves or other fire detection, suppression or control elements shall be identified for the use of the fire department. Approved signs required to identify fire protection equipment and equipment location shall be constructed of durable materials, permanently installed and readily visible.

    SECTION 915—CARBON MONOXIDE (CO) DETECTION

    [F] 915.1 General. Carbon monoxide (CO) detection shall be installed in new buildings in accordance with Section s 915.1.1 through 915.7. [Not adopted by HCD] Carbon monoxide detection shall be installed in existing buildings in accordance with Chapter 11 of the California Fire Code .

    Pursuant to Health and Safety Code Section 17926, carbon monoxide detection shall be installed in all existing Group R buildings as required in Section 915.

    Exception: Carbon monoxide detection is not required in Group S, Group F and Group U occupancies that are not normally occupied.

    [F] 915.1.1 Where required. Carbon monoxide detection shall be installed in the locations specified in Section 915.2 where any of the following conditions exist.

    1. In buildings that contain a CO source.
    2. In buildings that contain or are supplied by a CO-producing forced-air furnace.
    3. In buildings with attached private garages.
    4. In buildings that have a CO-producing vehicle that is used within the building.

    [F] 915.2 Locations. Carbon monoxide detection shall be installed in accordance with the manufacturer’s published instructions in the locations specified in Sections 915.2.1 through 915.2.3.

    [F] 915.2.1 Dwelling units. Carbon monoxide detection shall be installed in dwelling units in the following locations: 1. Outside of each separate sleeping area in the immediate vicinity of the bedrooms. 2. On every occupiable level of a dwelling unit, including basements. 3. Where a CO source is located within a bedroom or its attached bathroom, carbon monoxide detection shall be installed within the bedroom.

    [F] 915.2.2 Sleeping units. Carbon monoxide detection shall be installed in sleeping units.

    Exception: Carbon monoxide detection shall be allowed to be installed outside of each separate sleeping area in the immediate vicinity of the sleeping unit where the sleeping unit or its attached bathroom does not contain a CO source and is not served by a CO-producing forced-air furnace.

    [F] 915.2.3 Group E occupancies. A carbon monoxide system that uses carbon monoxide detectors shall be installed in Group E occupancies where classrooms include any of the conditions identified in Sections 915.1.2 through 915.1.6 . Alarm signals from carbon monoxide detectors shall be automatically transmitted to an on-site location as approved by the authority having jurisdiction.

  • CFC § 915.5.1 High relevance — show source text

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    FIRE PROTECTION AND LIFE SAFETY SYSTEMS

    915.5.1 General. Carbon monoxide detectors shall be listed in accordance with UL 2075.

    915.5.2 Locations. Carbon monoxide detectors shall be installed in the locations specified in Section 915.2. These locations supersede the locations specified in NFPA 72.

    915.5.3 Combination detectors. Combination carbon monoxide/smoke detectors shall be an acceptable alternative to carbon monoxide detectors, provided that they are listed in accordance with UL 268 and UL 2075.

    Combination carbon monoxide/smoke alarms shall comply with Section 915, and all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    915.5.4 Occupant notification. Activation of a carbon monoxide detector shall annunciate at the control unit and shall initiate audible and visible alarm notification throughout the building.

    Exception: Occupant notification is permitted to be limited to the area where the carbon monoxide alarm signal originated and other signaling zones in accordance with the fire safety plan, provided that the alarm signal from an activated carbon monoxide detector is automatically transmitted to an approved on-site location or off-premises location.

    915.5.5 Duct detection. Carbon monoxide detectors placed in environmental air ducts or plenums shall not be used as a substitute for the required protection in Section 915.

    915.6 Maintenance. Carbon monoxide alarms and carbon monoxide detection systems shall be maintained in accordance with NFPA 72. Carbon monoxide alarms and carbon monoxide detectors that become inoperable or begin producing end-of-life signals shall be replaced.

    915.6.1 Enclosed parking garages. Carbon monoxide and nitrogen dioxide detectors installed in enclosed parking garages in accordance with Section 403.7.2 of the California Mechanical Code shall be maintained in accordance with the manufacturer’s instructions and their listing. Detectors that become inoperable or begin producing end-of-life signals shall be replaced.

    915.7 Visible alarms. In buildings containing covered multifamily dwellings as defined in Chapter 2, all required carbon monoxide alarms shall be equipped with the capability to support visible alarm notification in accordance with NFPA 720.

    SECTION 916—GAS DETECTION SYSTEMS

    916.1 Gas detection systems. Gas detection systems required by this code shall comply with Sections 916.2 through 916.11.

    916.2 Permits. Permits shall be required as set forth in Section 105.6.11.

    916.2.1 Construction documents. Documentation of the gas detection system design and equipment to be used that demonstrates compliance with the requirements of this code shall be provided with the application for permit.

    916.3 Equipment. Gas detection system equipment shall be designed for use with the gases being detected and shall be installed in accordance with manufacturer’s instructions.

    916.4 Power connections. Gas detection systems shall be permanently connected to the building electrical power supply or shall be permitted to be cord connected to an unswitched receptacle using an approved restraining means that secures the plug to the receptacle.

    916.5 Emergency and standby power. Standby or emergency power shall be provided or the gas detection system shall initiate a trouble signal at an approved location if the power supply is interrupted.

    916.6 Sensor locations. Sensors shall be installed in approved locations where leaking gases are expected to accumulate.

  • CFC § 307.1 High relevance — show source text

    [HCD 1-AC] Accessibility requirements for covered multifamily dwellings, as defined in Chapter 2 of the California Building Code, are promulgated under HCD authority and are located in Chapter 11A of the California Building Code.

    SECTION 307—SMOKE ALARMS

    307.1 Smoke alarms. Where an alteration, addition, change of occupancy or relocation of a building is made to an existing building or structure of a Group R and I-1 occupancy, the existing building shall be provided with smoke alarms in accordance with the California Fire Code or Section R310 of the California Residential Code .

    Exception: Work classified as Level 1 Alterations in accordance with Chapter 7.

    SECTION 308—CARBON MONOXIDE DETECTION

    308.1 Carbon monoxide detection. Where an addition, alteration, change of occupancy or relocation of a building is made to an existing building, the existing building shall be provided with carbon monoxide detection in accordance with the California Fire Code or Section R311 of the California Residential Code .

    3-6 2025 CALIFORNIA EXISTING BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    PROVISIONS FOR ALL COMPLIANCE METHODS

    308.2 Carbon monoxide alarms in existing portions of a building. [HCD 1 & HCD 2] Pursuant to Health and Safety Code Section 17926, carbon monoxide detection shall be provided in all existing Group R buildings, as required in Section 915 of the California Building Code or Section R315 of the California Residential Code, as applicable.

    308.2.1 Carbon monoxide detection in existing Group E occupancy buildings. Where the new addition includes any of the conditions identified in the California Fire Code Sections 915.1.2 through 915.1.6, carbon monoxide detection shall be installed in accordance with Section 915 of the California Fire Code. No person shall install, market, distribute, offer for sale, or sell any carbon monoxide device in the State of California unless the device and instructions have been approved and listed by the Office of the State Fire Marshal.

    SECTION 309—ADDITIONS AND REPLACEMENTS OF EXTERIOR WALL COVERINGS AND EXTERIOR WALL ENVELOPES

    309.1 General. The provisions of Section 309 apply to all alterations, repairs, additions, relocations of structures and changes of occupancy regardless of compliance method.

    309.2 Additions and replacements. Where an exterior wall covering or exterior wall envelope is added or replaced, the materials and methods used shall comply with the requirements for new construction in Chapter 14 and Chapter 26 of the California Building Code if the added or replaced exterior wall covering or exterior wall envelope involves two or more contiguous stories and comprises more than 15 percent of the total wall area on any side of the building.

    309.2.1 Automatic sprinkler systems. Combustible exterior wall covering or combustible exterior wall envelopes shall not be added to an existing high-rise building that is not protected throughout with an automatic sprinkler system.

    Exceptions:

    1. Where such material is located on a single story and is less than 15 percent of the wall area on any side of the building.
    2. Water-resistive barriers installed in accordance with Section 1402.6 of the California Building Code .
  • CFC § 915.5 High relevance — show source text

    2. No construction is taking place. 3. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 4. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck. 5. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    [F] 915.5 Carbon monoxide detection systems. Carbon monoxide detection systems shall be an acceptable alternative to carbon monoxide alarms and shall comply with Sections 915.5.1 through 915.5.3.

    [F] 915.5.1 General. Carbon monoxide detectors shall be listed in accordance with UL 2075.

    [F] 915.5.2 Locations. Carbon monoxide detectors shall be installed in the locations specified in Section 915.2 or NFPA 72.

    [F] 915.5.3 Combination detectors. Combination carbon monoxide/smoke detectors shall be an acceptable alternative to carbon monoxide detectors, provided that they are listed in accordance with UL 268 and UL 2075.

    Combination carbon monoxide/smoke detectors shall comply with all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    [F] 915.5.4 Occupant notification. Activation of a carbon monoxide detector shall annunciate at the control unit and shall initiate audible and visible alarm notification throughout the building.

    Exception: Occupant notification is permitted to be limited to the area where the carbon monoxide alarm signal originated and other signaling zones in accordance with the fire safety plan, provided that the alarm signal from an activated carbon monoxide detector is automatically transmitted to an approved on-site location or off-premises location.

    [F] 915.5.5 Duct detection. Carbon monoxide detectors placed in environmental air ducts or plenums shall not be used as a substitute for the required protection in Section 915.

    [F] 915.6 Maintenance. Carbon monoxide alarms and carbon monoxide detection systems shall be maintained in accordance with NFPA 72. Carbon monoxide alarms and carbon monoxide detectors that become inoperable or begin producing end-of-life signals shall be replaced.

    915.6.1 Enclosed parking garages. Carbon monoxide and nitrogen dioxide detectors installed in enclosed parking garages in accor- dance with Section 403.7.2 of the California Mechanical Code shall be maintained in accordance with the manufacturer’s instructions and their listing. Detectors that become inoperable or begin producing end-of-life signals shall be replaced.

    915.7 Visible alarms. In buildings containing covered multifamily dwellings as defined in Chapter 2, all required carbon monoxide alarms shall be equipped with the capability to support visible alarm notification in accordance with NFPA 72.

    SECTION 916—GAS DETECTION SYSTEMS

    [F] 916.1 Gas detection systems. Gas detection systems required by this code shall comply with Sections 916.2 through 916.11.

    [F] 916.2 Permits. Permits shall be required as set forth in Section 105.6.10 of the California Fire Code .

  • CFC § 915.4.2 High relevance — show source text

    Exceptions:

    1. Where installed in buildings without commercial power, battery-powered carbon monoxide alarms shall be an acceptable alternative. 2. Carbon monoxide alarms in Group R occupancies shall be permitted to receive their primary power from other power sources recognized for use by NFPA 720. 3. Carbon monoxide alarms in Group R occupancies shall be permitted to be battery-powered or plug-in with a battery backup in existing buildings built prior to January 1, 2011, under any of the following conditions: 3.1. No construction is taking place. 3.2. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 3.3. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck. 3.4. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    915.4.2 Listings. Residential carbon monoxide alarms shall be listed in accordance with UL 2034.

    No person shall install, market, distribute, offer for sale or sell any carbon monoxide device in the State of California unless the device and instructions have been approved and listed by the Office of the State Fire Marshal.

    915.4.3 Combination alarms. Combination carbon monoxide/smoke alarms shall be an acceptable alternative to carbon monoxide alarms. Combination carbon monoxide/smoke alarms shall be listed in accordance with UL 217 and UL 2034. Combination carbon monoxide/smoke alarms shall comply with Section 915, and all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    915.4.4 Interconnection. Where more than one carbon monoxide alarm is required to be installed within a dwelling unit or within a sleeping unit in Group R occupancies, the alarms shall be interconnected in a manner that activation of one alarm shall activate all of the alarms in the individual unit.

    Exception : Interconnection is not required in existing buildings, built prior to January 1, 2011, under any of the following conditions: 1. Physical interconnection is not required where listed wireless alarms are installed and all alarms sound upon activation of one alarm.

    2. No construction is taking place. 3. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 4. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding or the addition or replacement of windows or doors, or the addition of a porch or deck. 5. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    915.5 Carbon monoxide detection systems. Carbon monoxide detection systems shall be an acceptable alternative to carbon monoxide alarms and shall comply with Sections 915.5.1 through 915.5.3.

    9-76 2025 CALIFORNIA FIRE CODE

  • CFC § 915.3.1 High relevance — show source text

    915.3.1 Alarm limitations. Carbon monoxide alarms shall only be installed in dwelling units and in sleeping units. They shall not be installed in locations where the code requires carbon monoxide detectors to be used.

    915.3.2 Fire alarm system required. New buildings that are required by Section 907.2 to have a fire alarm system and by Section 915.2 to have carbon monoxide detectors shall be connected to the fire alarm system in accordance with NFPA 72.

    915.3.3 Fire alarm systems not required. In new buildings that are not required by Section 907.2 to have a fire alarm system, carbon monoxide detection shall be provided by one of the following:

    1. Carbon monoxide detectors connected to an approved carbon monoxide detection system in accordance with NFPA 72.
    2. Carbon monoxide detectors connected to an approved combination system in accordance with NFPA 72.
    3. Carbon monoxide detectors connected to an approved fire alarm system in accordance with NFPA 72.
    4. Where approved by the fire code official, carbon monoxide alarms maintained in accordance with the manufacturer’s instructions.

    915.3.4 Installation. Carbon monoxide detection shall be installed in accordance with NFPA 72 and the manufacturer’s instructions.

    915.4 Carbon monoxide alarms. Carbon monoxide alarms shall comply with Sections 915.4.1 through 915.4.4.

    915.4.1 Power source. Carbon monoxide alarms shall receive their primary power from the building wiring where such wiring is served from a commercial source, and when primary power is interrupted, shall receive power from a battery. Wiring shall be permanent and without a disconnecting switch other than that required for overcurrent protection.

    Exceptions:

    1. Where installed in buildings without commercial power, battery-powered carbon monoxide alarms shall be an acceptable alternative. 2. Carbon monoxide alarms in Group R occupancies shall be permitted to receive their primary power from other power sources recognized for use by NFPA 720. 3. Carbon monoxide alarms in Group R occupancies shall be permitted to be battery-powered or plug-in with a battery backup in existing buildings built prior to January 1, 2011, under any of the following conditions: 3.1. No construction is taking place. 3.2. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 3.3. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck. 3.4. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    915.4.2 Listings. Residential carbon monoxide alarms shall be listed in accordance with UL 2034.

    No person shall install, market, distribute, offer for sale or sell any carbon monoxide device in the State of California unless the device and instructions have been approved and listed by the Office of the State Fire Marshal.

  • CFC § 915.4 High relevance — show source text

    [F] 915.4 Carbon monoxide alarms. Carbon monoxide alarms shall comply with Sections 915.4.1 through 915.4.5 .

    [F] 915.4.1 Power source. Carbon monoxide alarms shall receive their primary power from the building wiring where such wiring is served from a commercial source, and when primary power is interrupted, shall receive power from a battery. Wiring shall be permanent and without a disconnecting switch other than that required for overcurrent protection.

    Exception s :

    1. Where installed in buildings without commercial power, battery-powered carbon monoxide alarms shall be an acceptable alternative. 2. Carbon monoxide alarms in Group R occupancies shall be permitted to receive their primary power from other power sources recognized for use by NFPA 72. 3. Carbon monoxide alarms in Group R occupancies shall be permitted to be battery-powered or plug-in with a battery backup in existing buildings built prior to January 1, 2011, under any of the following conditions: 3.1. No construction is taking place. 3.2. Repairs or alterations do not result in the removal of interior wall and ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required. 3.3. Repairs or alterations are limited to the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck. 3.4. Work is limited to the installation, alteration or repair of plumbing, mechanical or electrical systems, which do not result in the removal of interior wall or ceiling finishes exposing the structure in areas/spaces where carbon monoxide alarms are required.

    2025 CALIFORNIA BUILDING CODE 9-57

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    �

    �

    FIRE PROTECTION AND LIFE SAFETY SYSTEMS

    [F] 915.4.2 Listings. Residential Carbon monoxide alarms shall be listed in accordance with UL 2034.

    No person shall install, market, distribute, offer for sale, or sell any carbon monoxide device in the State of California unless the device and instructions have been approved and listed by the Office of the State Fire Marshal.

    [F] 915.4.3 Combination alarms. Combination carbon monoxide/smoke alarms shall be an acceptable alternative to carbon monoxide alarms. Combination carbon monoxide/smoke alarms shall be listed in accordance with UL 217 and UL 2034.

    Combination carbon monoxide/smoke alarms shall comply with Section 915, and all requirements for listing and approval by the Office of the State Fire Marshal for smoke alarms.

    [F] 915.4.4 Interconnection. Where more than one carbon monoxide alarm is required to be installed within a dwelling unit or within a sleeping unit in Group R occupancies, the alarms shall be interconnected in a manner that activation of one alarm shall activate all of the alarms in the individual unit.

    Exception: Interconnection is not required in existing buildings, built prior to January 1, 2011, under any of the following conditions:

    1. Physical interconnection is not required where listed wireless alarms are installed and all alarms sound upon activation of one alarm.

Frequently asked questions

Do I have to put a CO detector inside each bedroom?

Not usually. The code requires a detector outside of each separate sleeping area in the immediate vicinity of the bedrooms and on every occupiable level; only when a CO source is located within a bedroom (or attached bathroom) must a detector be installed inside that bedroom. § 915.2.1(1)–(3).

Can I use combination smoke/CO alarms?

Yes—combination CO/smoke detectors are allowed provided they are listed per the applicable UL standards and meet State approval/listing requirements described in § 915.5.3.

Are duct‑mounted CO detectors acceptable in place of room detectors?

No. Duct or plenum detectors shall not be used as a substitute for the required area protection in Section 915. § 915.5.5.

Who decides exact mounting locations and spacing?

The code defers mounting/placement specifics to the manufacturer’s published instructions and referenced standards; see § 915.2 and maintenance reference § 915.6 (NFPA 72).

How often must CO detectors be replaced or tested?

The code requires maintenance in accordance with NFPA 72 and says inoperable or end‑of‑life devices must be replaced — the NFPA 72 schedule and device manufacturer instructions specify testing intervals and end‑of‑life timing. § 915.6.

More in California Fire Code

Ask about the CFC

Get cited, plain-English answers on the California Fire Code for your project — any code section, any scenario.

Start Free Trial

Related in the CFC

What are the standpipe, fire pump and secondary water supply requirements (including high-rise)?

What rules apply to alternative fixed fire‑extinguishing systems (CO2, clean agents, water mist)?

Special & Alternative Systems (standpipes, extinguishing, CO, pumps)

California Fire Code