CMC · California Mechanical Code

Where are refrigerant detectors required and what alarm thresholds stop equipment?

Homeowner summary: Refrigeration machinery rooms must have detectors where leaks will collect; detectors must alarm at or below worker exposure limits (OELs) and, for flammable refrigerants, automatically stop compressors/pumps if concentration reaches the detector’s upper limit or 25% of the refrigerant’s lower flammable limit — check the equipment data and the Authority Having Jurisdiction for exact set points and detector locations.

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

  • Refrigerant detectors are required in refrigeration machinery rooms and installed “in areas where refrigerant from a leak will concentrate,” and they must actuate alarms and mechanical ventilation at set points tied to the Occupational Exposure Limit (OEL) or other limits as specified by the code (§ 1106.2.5) .
  • The detectors must meet performance and response-time requirements (automatic self-test, one or more set points, response time) in § 1106.2.6 and the Fire Code requires detectors to alarm at the lesser of the TLV‑TWA (OEL) or 25% of the LFL, and to stop equipment when concentration exceeds the detector’s upper detection limit or 25% of the LFL, whichever is lower (§ 608.9.1) .

Detectors must be placed where leaks collect, alarm at or below the OEL (or the lesser TLV/25% LFL), and—when concentrations reach the detector’s upper limit or 25% LFL—refrigeration equipment must be shut off.

Requirements in detail

Where detectors are required (location)

  • Install one or more refrigerant detectors inside each refrigeration machinery room, located in the places where leaked refrigerant is expected to concentrate (low points for heavy refrigerants, high points for light refrigerants). § 1106.2.5 requires the detector(s) be “located in areas where refrigerant from a leak will concentrate.”
  • Exception: rooms containing only R‑718 (water) do not require refrigerant detectors; Group A2L/B2L have additional requirements (see Exceptions & special cases). § 1106.2.5 .

Detector performance & response

  • Detectors must perform automatic self‑testing with a visible trouble signal on sensor failure, and must provide one or more set points for required responses. § 1106.2.6 .
  • General response-time requirement (non‑A2L/B2L special path): detector responses shall be activated within 30 seconds after exposure exceeds the set point in § 1106.2.5/§ 1107.1.7 (§ 1106.2.6(3)) .
  • For A2L/B2L machinery rooms (Section 1106.11) different set points and response-time table values apply (see table row citations below). .

Alarm levels and what they do

  • Alarms and ventilation must be arranged so that:
    • A detector set at or below the OEL produces an alarm and ventilation action (trouble-type alarm, automatic reset per the ASHRAE table adopted at § 1106.11.10.2) .
    • Detection at the detector’s upper detection limit or at 25% of the LFL (whichever is lower) must cause automatic shutdown of equipment in the machinery room (compressors, pumps, normally‑closed automatic refrigerant valves, and other ignition sources as listed) — see § 608.9.1 and § 608.10.1 (Fire Code) and the CMC references for machinery room shutdown. .

Quick decision table (decision‑relevant dimensions / values)

Decision item Code requirement / threshold What happens Code Reference
Where required Detectors in each refrigeration machinery room and at locations where leaked refrigerant concentrates Alarm + ventilation activation required § 1106.2.5
Primary alarm set point Not more than the OEL (TLV‑TWA) or as approved by AHJ Annunciate visual & audible alarms; ventilate § 1106.2.5
Equipment‑shutdown threshold Upper detection limit of detector OR 25% of the LFL, whichever is lower Automatic stop of compressors, pumps, normally‑closed valves, other ignition sources per list § 608.9.1 and § 608.10.1
Detector self‑test & trouble signal Automatic self‑test; trouble signal if failure Service required / monitored trouble § 1106.2.6(1)
General detector response time ≤ 30 seconds after exposure above set point (general CMC detectors) Timely alarm/ventilation/action § 1106.2.6(3)
A2L/B2L special detector timing Tableed: ≤ 300 s for OEL set point (trouble/auto); ≤ 15 s for RCL set point (emergency/manual) — see table Level‑1 (auto) vs Level‑2 (manual) alarm & ventilation rates § 1106.11.10.2 (Table 1106.11.10.2)
Alarm reset type Manual reset required for emergency alarms; reset located inside machinery room (required alarms are manual reset) Prevent automatic restart until inspected § 1106.2.5 and § 1106.11.10.2

Exceptions & special cases

  • R‑718 (water) systems: refrigerant detectors are not required where only R‑718 is present (§ 1106.2.5) .
  • Group A2L and B2L refrigerants: detectors and alarm/ventilation responses for A2L/B2L machinery rooms follow the special machinery‑room provisions in Section 1106.11 (including Table 1106.11.10.2 response times and alarm types). See § 1106.11 for the stricter timing/ventilation/alarm reset rules. .
  • Fire Code coordination: the California Fire Code (Chapter 6, Section 608) requires detectors to initiate alarms at the lesser of the TLV‑TWA or 25% LFL and requires automatic shutdown when the upper detection limit or 25% LFL is exceeded; when the Fire Code applies it should be read together with the CMC requirements (§ 608.9.1, § 608.10.1) .

Common mistakes

  • Assuming the same response time applies in all cases — the general CMC detector response limit is 30 seconds (§ 1106.2.6(3)), but the A2L/B2L machinery‑room table uses ≤ 300 s and ≤15 s for different set points — read the correct subsection for your refrigerant group. .
  • Confusing OEL/TLV‑TWA, RCL, and LFL/LEL thresholds — detectors used for worker exposure (OEL) have different intent and alarm/reset behavior than detectors or shutdown thresholds tied to flammability (percent of LFL). Always identify which limit the alarm is addressing and cite the AHJ‑approved OEL where required (§ 1106.2.5, § 608.9.1). .
  • Forgetting manual‑reset requirement location — required alarms are manual reset and the reset must be located inside the machinery room (§ 1106.2.5) .
  • Using multiport sampling in certain A2L/B2L detector installations — multiport-type devices are prohibited for the 1106.11 detectors; follow the machinery‑room specific detector requirements if using A2L/B2L refrigerants (§ 1106.11.8–9) .

Worked example — concrete scenario (illustrative only)

Scenario: a refrigeration machinery room uses a flammable refrigerant whose LFL is specified on the equipment data sheet (consult manufacturer/MSDS for the actual LFL). For this example only we will use an assumed LFL = 4.0% by volume (you must obtain the real LFL for your refrigerant).

  • Code trigger for shutdown: 25% of LFL = 0.25 × 4.0% = 1.0% by volume. The Fire Code requires automatic shutdown when concentration exceeds the detector’s upper detection limit or 25% LFL, whichever is lower (§ 608.9.1, § 608.10.1) .
  • Detector selection/setting: set detector set points so that:
    • A first (OEL‑level) alarm is at or below the applicable OEL (worker exposure alarm). That alarm must annunciate visual/audible signals and trigger Level‑1 ventilation actions per § 1106.2.5. If the OEL exceeds 1.0% in this example, the shutdown threshold (1.0%) is still the relevant flammable shutdown point because it is the lesser of (upper detector limit or 25% LFL) — equipment will stop at 1.0% if that is lower than the detector upper limit. .
  • Response time: for a standard CMC detector use the ≤ 30 s activation requirement for the set point response in § 1106.2.6(3); if the refrigerant is A2L/B2L follow the timing in Table 1106.11.10.2 (≤300 s for OEL, ≤15 s for RCL emergency alarm) instead. .

Note: the numeric LFL used above is illustrative only. The Code requires use of the refrigerant’s actual LFL/TLV/OEL values from manufacturer data, ASHRAE tables, or AHJ‑approved sources when setting detector levels (see the cited sections) .

Related provisions

  • § 1106.2.5 — Detectors & alarms required in refrigeration machinery rooms (CMC) .
  • § 1106.2.6 — Refrigerant detector performance, self‑test, response time (CMC) .
  • § 1106.11 (and Table 1106.11.10.2) — Special machinery‑room detection/response rules for Group A2L/B2L refrigerants (CMC) .
  • § 608.9.1 — Refrigerant detection for refrigerants other than ammonia; alarm thresholds (lesser of TLV‑TWA or 25% LFL) and shutdown requirement (Fire Code) .
  • § 608.10.1 — Emergency remote shutoff and automatic shutdown at upper detection limit or 25% LEL (Fire Code) .
  • § 1107.1.7.2 — Machinery room equipment shutdown triggered at 25% of LFL or detector upper limit (CMC special machinery‑room rules) .

Code references

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

  • CMC § 7.25 High relevance — show source text

    7.25 feet (2210 mm) below equipment situated over passageways. [ASHRAE 15:8.11.1]

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    REFRIGERATION

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    1106.2.2 Openings. Each refrigeration machinery room shall have a tight-fitting door or doors opening outward, self-closing where they open into the building and adequate in number to ensure freedom for persons to escape in an emergency. With the exception of access doors and panels in air ducts and air-handling units in accordance with Section 1106.2.3, there shall be no openings that will permit passage of escaping refrigerant to other parts of the building. [ASHRAE 15:8.11.2]

    1106.2.3 Airflow. There shall be no airflow to or from an occupied space through a machinery room unless the air is ducted and sealed in such a manner as to prevent any refrigerant leakage from entering the airstream. Access doors and panels in ductwork and air-handling units shall be gasketed and tight fitting. [ASHRAE 15:8.11.3]

    1106.2.4 Restricted Access. Access to the refrigeration machinery room shall be restricted to authorized personnel. Doors shall be clearly marked, or permanent signs shall be posted at each entrance to indicate this restriction. [ASHRAE 15:8.11.4]

    1106.2.5 Detectors and Alarms. Each refrigeration machinery room shall contain one or more refrigerant detectors in accordance with Section 1106.2.6, located in areas where refrigerant from a leak will concentrate, that actuate an alarm and mechanical ventilation in accordance with Section 1106.2.7 at a set point not more than the corresponding Occupational Exposure Limit, OEL, in accordance with Table 1102.3, a set point determined in accordance with the OEL as defined in Chapter 2 shall be approved by the Authority Having Jurisdiction. The alarm shall annunciate visual and audible alarms inside the refrigeration machinery room and outside each entrance to the refrigeration machinery room. The alarms required in this section shall be of the manual reset type with the reset located inside the refrigeration machinery room. Alarms set at other levels, such as IDLH, and automatic reset alarms shall be permitted in addition to those required in accordance with this section. The meaning of each alarm shall be clearly marked by signage near the annunciator.

    Exception: Refrigerant detectors are not required where only systems using R-718 (water) are located in the refrigeration machinery room. For Group A2L and B2L, refrigerant detectors shall comply with Section 1106.11.

    1106.2.6 Refrigerant Detectors. Refrigerant detectors required in accordance with Section 1106.2.5 or Section 1107.1.7 shall meet all of the following conditions:

    (1) The refrigerant detector shall perform automatic self-testing of sensors. Where a failure is detected, a trouble signal shall be activated.

    (2) The refrigerant detector shall have one or more set points to activate responses in accordance with Section 1106.2.5 or Section 1107.1.7.

  • CMC § 1106.2.5 High relevance — show source text

    (1) Combustion air shall be ducted from outside the machinery room and sealed in such a manner as to prevent refrigerant leakage from entering the combustion chamber.

    (2) A refrigerant detector, that is in accordance with Section 1106.2.5, shall be installed to automatically shut down the combustion process in the event of refrigerant leak age.

    Exception: Machinery rooms where carbon dioxide (R-744) or water (R-718) is the refrigerant.

    1106.6 Ventilation Intake. Makeup air intakes to replace the exhaust air shall be provided to the refrigeration machinery room directly from outside the building. Intakes shall be located as required by other sections of the code and fitted with backdraft dampers or other approved flow-control means to prevent reverse flow. Distribution of makeup air shall be arranged to provide thorough mixing within the refrigeration machinery room to prevent short circuiting of the makeup air directly to the exhaust.

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    REFRIGERATION

    1106.11.6.1 Mechanical Ventilation. The machinery room shall have a mechanical ventilation system in accordance with Section 1106.11.11. The mechanical ventilation system shall:

    (1) Run continuously, and failure of the mechanical ventilation system actuates an alarm, or

    (2) Be activated by one or more refrigerant detectors, conforming to requirements of Section 1106.11.8. [ASHRAE 15:8.13.6.1] 1106.11.6.2 Detection System. Detection of refrigerant concentration that exceeds 25 percent of the LFL or the upper detection limit of the refrigerant detector, whichever is lower, shall automatically de-energize the following equipment in the machin ery room:

    (1) Refrigerant compressors

    (2) Refrigerant pumps

    (3) Normally closed automatic refrigerant valves

    (4) Other unclassified electrical sources of ignition with apparent power rating greater than 1 kVA, where the apparent power is the product of the circuit voltage and current rating. [ASHRAE 15:8.13.6.2] 1106.11.7 Mechanical Equipment Control. Remote control of the mechanical equipment in the refrigerating machinery room shall be provided immediately outside the machinery room door solely for the purpose of shutting down the equipment in an emergency. Ventilation fans shall be on a separate electrical circuit and have a control switch located immediately outside the machinery room door. [ASHRAE 15:8.13.7] 1106.11.8 Refrigerant Detectors. Each refrigerating machinery room in accordance with Section 1106.11 shall contain one or more refrigerant detectors in accordance with Section 1106.11.9. The detector(s) sensing element shall be located in areas where refrigerant from a leak will concentrate, with one or more set points that activate responses in accordance with Section 1106.11.10 for alarms and Section 1106.11.11 for mechanical ventilation. Multiport-type devices shall be prohibited. {ASHRAE 15:8.13.8} 1106.11.9 Refrigerant Detectors Requirements. Refrigerant detectors required by Section 1106.11 shall meet all of the following conditions:

  • CMC § 1107.1.7.1 High relevance — show source text

    1107.1.7.1 Mechanical Ventilation. The mechanical ventilation system in the machinery room is run continuously in accordance with Section 1106.11.6.1 and failure of the mechanical ventilation system actuates an alarm, or the mechanical ventilation system in the machinery room is activated by one or more refrigerant detectors, in accordance with the requirements of Section 1106.11.11.

    1107.1.7.2 Refrigeration Detectors. For the refrigerant detection required in Section 1106.2.5, detection of refrigerant concentration that exceeds 25 percent of the LFL or the upper detection limit of the refrigerant detector, whichever is lower, shall automatically de-energize the following equipment in the machinery room:

    (1) refrigerant compressors

    (2) refrigerant pumps

    (3) normally-closed automatic refrigerant valves

    1107.1.7.3 Machinery Rooms. The machinery room shall comply with Section 1106.11. 1107.1.8 Group A2, A3, B2, or B3 Refrigerants. Where any refrigerant of Groups A2, A3, B2, or B3 are used, the machinery room shall comply with Class 1, Division 2, of of the California Electrical Code .

    1107.1.9 Refrigeration Systems. As part of the mechanical ventilation system in accordance with Section 1106.2.8, refrigeration systems that contain more

    than 110 pounds (50 kg) of any Group A2L, A2, A3, B2L, B2, or B3, refrigerant shall have not less than one exhaust air inlet located adjacent to each system not more than 9 feet (3 m) away.

    1107.1.10 Remote Control. Remote control of the

    mechanical equipment in the refrigeration machinery room shall be provided immediately outside the machinery room door solely for the purpose of shutting down the equipment in an emergency. Ventilation fans shall be on a separate electrical circuit and have a control switch located immediately outside the machinery room door.

    1108.0 Refrigeration Machinery Room Equipment and Controls.

    1108.1 General. Equipment, piping, ducts, vents, or similar devices that are not essential for the refrigeration process, maintenance of the equipment, or for the illumination, ventilation, or fire protection of the room shall not be placed in or pass through a refrigeration machinery room.

    1108.2 Electrical. Electrical equipment and installations shall comply with California Electrical Code . The refrigeration machinery room shall not be classified as a hazardous location except as provided in Section 1107.1.7 or Section 1107.1.8.

    1108.3 Emergency Shutoff. A clearly identified emergency shutoff switch of the break-glass type or with an approved tamper-resistant cover shall be provided immediately adjacent to and outside of the principal refrigeration machinery room entrance. The switch shall provide off-only control of refrigerant compressors, refrigerant pumps, and normally-closed automatic refrigerant valves located in the machinery room. For other than A1 and B1 refrigerants, emergency shutoff shall be automatically activated by refrigerant Alarm 2 in accordance with Section 1106.2.5.

  • CMC § 608.7 High relevance — show source text

    608.7 Testing of equipment. Refrigeration equipment and systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be subject to periodic testing in accordance with Section 608.7.1. Records of tests shall be maintained. Tests of emergency devices or systems required by this chapter shall be conducted by persons trained and qualified in refrigeration systems.

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    608.7.1 Periodic testing. The following emergency devices or systems shall be periodically tested in accordance with the manufacturer’s instructions and as required by the fire code official.

    1. Treatment and flaring systems.
    2. Valves and appurtenances necessary to the operation of emergency refrigeration control boxes.
    3. Fans and associated equipment intended to operate emergency ventilation systems.
    4. Detection and alarm systems.

    608.8 Emergency signs. Refrigeration units or systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be provided with approved emergency signs, charts and labels in accordance with NFPA 704. Hazard signs shall be in accordance with the California Mechanical Code for the classification of refrigerants listed therein.

    608.9 Refrigerant detection. Machinery rooms shall be provided with a refrigerant detector with an audible and visible alarm. Where ammonia is used as the refrigerant, detection shall comply with IIAR 2. For refrigerants other than ammonia, refrigerant detection shall comply with Section 608.9.1.

    608.9.1 Refrigerants other than ammonia. A detector, or a sampling tube that draws air to a detector, shall be provided at an approved location where refrigerant from a leak is expected to accumulate. The system shall be designed to initiate audible and visible alarms inside of and outside each entrance to the refrigerating machinery room and transmit a signal to an approved location where the concentration of refrigerant detected exceeds the lesser of the following:

    1. The corresponding TLV-TWA values shown in the California Mechanical Code for the refrigerant classification.
    2. Twenty-five percent of the lower flammable limit (LFL).

    Detection of a refrigerant concentration exceeding the upper detection limit or 25 percent of the lower flammable limit (LFL), whichever is lower, shall stop refrigerant equipment in the machinery room in accordance with Section 608.10.1.

    608.10 Remote controls. Where flammable refrigerants are used and compliance with Section 1106 of the California Mechanical Code is required, remote control of the mechanical equipment and appliances located in the machinery room as required by Sections 608.10.1 and 608.10.2 shall be provided at an approved location immediately outside the machinery room and adjacent to its principal entrance.

    608.10.1 Refrigeration system emergency shutoff. A clearly identified switch of the break-glass type or with an approved tamperresistant cover shall provide off-only control of refrigerant compressors, refrigerant pumps and normally closed automatic refrigerant valves located in the machinery room. Additionally, this equipment shall be automatically shut off when the refrigerant vapor concentration in the machinery room exceeds the vapor detector’s upper detection limit or 25 percent of the LEL, whichever is lower.

  • CMC § 608.9.1 High relevance — show source text

    608.9.1 Refrigerants other than ammonia. A detector, or a sampling tube that draws air to a detector, shall be provided at an approved location where refrigerant from a leak is expected to accumulate. The system shall be designed to initiate audible and visible alarms inside of and outside each entrance to the refrigerating machinery room and transmit a signal to an approved location where the concentration of refrigerant detected exceeds the lesser of the following:

    1. The corresponding TLV-TWA values shown in the California Mechanical Code for the refrigerant classification.
    2. Twenty-five percent of the lower flammable limit (LFL).

    Detection of a refrigerant concentration exceeding the upper detection limit or 25 percent of the lower flammable limit (LFL), whichever is lower, shall stop refrigerant equipment in the machinery room in accordance with Section 608.10.1.

    608.10 Remote controls. Where flammable refrigerants are used and compliance with Section 1106 of the California Mechanical Code is required, remote control of the mechanical equipment and appliances located in the machinery room as required by Sections 608.10.1 and 608.10.2 shall be provided at an approved location immediately outside the machinery room and adjacent to its principal entrance.

    608.10.1 Refrigeration system emergency shutoff. A clearly identified switch of the break-glass type or with an approved tamperresistant cover shall provide off-only control of refrigerant compressors, refrigerant pumps and normally closed automatic refrigerant valves located in the machinery room. Additionally, this equipment shall be automatically shut off when the refrigerant vapor concentration in the machinery room exceeds the vapor detector’s upper detection limit or 25 percent of the LEL, whichever is lower.

    608.10.2 Ventilation system. A clearly identified switch of the break-glass type or with an approved tamper-resistant cover shall provide on-only control of the machinery room ventilation fans.

    608.11 Emergency pressure control system. Permanently installed refrigeration systems in machinery rooms containing more than 6.6 pounds (3 kg) of flammable, toxic or highly toxic refrigerant or ammonia shall be provided with an emergency pressure control system in accordance with Sections 608.11.1 and 608.11.2.

    608.11.1 Automatic crossover valves. Each high- and intermediate-pressure zone in a refrigeration system shall be provided with a single automatic valve providing a crossover connection to a lower pressure zone. Automatic crossover valves shall comply with Sections 608.11.1.1 through 608.11.1.3.

    608.11.1.1 Overpressure limit set point. Automatic crossover valves shall be arranged to automatically relieve excess system pressure to a lower pressure zone if the pressure in a high- or intermediate-pressure zone rises to within 90 percent of the set point for emergency pressure relief devices.

    608.11.1.2 Manual operation. Where required by the fire code official, automatic crossover valves shall be capable of manual operation.

    608.11.1.3 System design pressure. Refrigeration system zones that are connected to a higher pressure zone by an automatic crossover valve shall be designed to safely contain the maximum pressure that can be achieved by interconnection of the two zones.

    608.11.2 Automatic emergency stop. An automatic emergency stop feature shall be provided in accordance with Sections 608.11.2.1 and 608.11.2.2.

  • CMC § 1106.11.11.4 High relevance — show source text

    1106.11.11.4 Level 2 Ventilation Rate. When required by Section 1106.11.11.3, the total airflow for Level 2 ventilation shall be not less than the airflow rate determined by Figure 1106.11.11.4.

    [ASHRAE 15:8.13.11.4]

    1107.0 Machinery Room, Special Requirements.

    1107.1 General. In cases specified in the rules of Section 1106.1, a refrigeration machinery room shall comply with the special requirements in accordance with Section 1107.1.1 through Section 1107.1.10, in addition to Section 1106.2.

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    1107.1.1 Flame-Producing Devices. There shall be no flame-producing device or continuously operating hot surface over 800°F (427°C) permanently installed in the room.

    1107.1.2 Doors. Doors communicating with the building shall be approved, self-closing, tight-fitting fire doors.

    1107.1.3 Walls, Floors, and Ceilings. Walls, floor, and ceiling shall be tight and of noncombustible construction. Walls, floor, and ceiling separating the refrigeration machinery room from other occupied spaces shall be not less than one-hour fire-resistive construction.

    1107.1.4 Machinery Rooms. The refrigeration machinery room shall have a door that opens directly to the outdoors or through a vestibule equipped with selfclosing, tight-fitting doors. 1107.1.5 Exterior Openings. Exterior openings, where present, shall not be under a fire escape or an open stair way. 1107.1.6 Sealing. All pipes piercing the interior walls, ceiling, or floor of such rooms shall be tightly sealed to the walls, ceiling, or floor through which they pass. 1107.1.7 Group A2L and B2L Refrigerants. Where refrigerant of Groups A2L or B2L are used, the requirements of Class 1, Division 2, of the California Electrical Code, shall not apply to the machinery room provided that the conditions in Section 1107.1.7.1 through Section 1107.1.7.3 are met.

    1107.1.7.1 Mechanical Ventilation. The mechanical ventilation system in the machinery room is run continuously in accordance with Section 1106.11.6.1 and failure of the mechanical ventilation system actuates an alarm, or the mechanical ventilation system in the machinery room is activated by one or more refrigerant detectors, in accordance with the requirements of Section 1106.11.11.

    1107.1.7.2 Refrigeration Detectors. For the refrigerant detection required in Section 1106.2.5, detection of refrigerant concentration that exceeds 25 percent of the LFL or the upper detection limit of the refrigerant detector, whichever is lower, shall automatically de-energize the following equipment in the machinery room:

    (1) refrigerant compressors

    (2) refrigerant pumps

    (3) normally-closed automatic refrigerant valves

  • CMC § 608.13.7 High relevance — show source text

    608.13.7 Ammonia diffusion systems. Ammonia diffusion systems shall include a tank containing 1 gallon of water for each pound of ammonia (8.3 L of water for each 1 kg of ammonia) that will be released in 1 hour from the largest relief device connected to the discharge pipe. The water shall be prevented from freezing. The discharge pipe from the pressure relief device shall distribute ammonia in the bottom of the tank, but not lower than 33 feet (10 058 mm) below the maximum liquid level. The tank shall contain the volume of water and ammonia without overflowing.

    608.14 Mechanical ventilation exhaust. Exhaust from mechanical ventilation systems serving refrigeration machinery rooms containing flammable, toxic or highly toxic refrigerants, other than ammonia, capable of exceeding 25 percent of the LFL or 50 percent of the IDLH shall be equipped with approved treatment systems to reduce the discharge concentrations to those values or lower.

    Exception: Refrigeration systems containing Group A2L complying with Section 608.18.

    608.15 Notification of refrigerant discharges. The fire code official shall be notified immediately when a discharge becomes reportable under state, federal or local regulations in accordance with Section 5003.3.1.

    608.16 Records. A record of refrigerant quantities brought into and removed from the premises shall be maintained.

    [M] 608.17 Electrical equipment. Where refrigerant of Groups A2, A3, B2 and B3, as defined in the California Mechanical Code, are used, refrigeration machinery rooms shall conform to the Class I, Division 2, hazardous location classification requirements of the California Electrical Code.

    Exception: Ammonia machinery rooms that are provided with ventilation in accordance with Section 1101.1.2 of the California Mechanical Code .

    [M] 608.18 Group A2L and B2L refrigerant. Machinery rooms for Group A2L and B2L refrigerant shall comply with Sections 1106.4.1 through 1106.4.3 of the California Mechanical Code .

    608.18.1 Elevated temperatures. Open flame-producing devices or continuously operating hot surfaces over 1,290°F (700°C) shall not be permanently installed in the room.

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    [M] 608.18.2 Refrigerant detector. In addition to the requirements of Section 1105.3 of the California Mechanical Code, refrigerant detectors shall signal an alarm and activate the ventilation system in accordance with the response time specified in Table 608.18.2.

    TABLE 608.18.2—GROUP A2L AND B2L DETECTOR ACTIVATION Col2 Col3 Col4 Col5
    ACTIVATION LEVEL MAXIMUM
    RESPONSE TIME (seconds)    		 ASHRAE 15
    VENTILATION LEVEL    		 ALARM RESET ALARM TYPE
    Less than or equal to the OEL in Table 1103.1 of the
    California Mechanical Code    		 300 1 Automatic Trouble
    Less than or equal to the refrigerant concentration level
    in Table 1103.1 of the_California Mechanical Code_    		 15 2 Manual Emergency
  • CMC § 1106.11. High relevance — show source text

    The alarm shall annunciate visual and audible alarms inside the refrigeration machinery room and outside each entrance to the refrigeration machinery room. The alarms required in this section shall be of the manual reset type with the reset located inside the refrigeration machinery room. Alarms set at other levels, such as IDLH, and automatic reset alarms shall be permitted in addition to those required in accordance with this section. The meaning of each alarm shall be clearly marked by signage near the annunciator.

    Exception: Refrigerant detectors are not required where only systems using R-718 (water) are located in the refrigeration machinery room. For Group A2L and B2L, refrigerant detectors shall comply with Section 1106.11.

    1106.2.6 Refrigerant Detectors. Refrigerant detectors required in accordance with Section 1106.2.5 or Section 1107.1.7 shall meet all of the following conditions:

    (1) The refrigerant detector shall perform automatic self-testing of sensors. Where a failure is detected, a trouble signal shall be activated.

    (2) The refrigerant detector shall have one or more set points to activate responses in accordance with Section 1106.2.5 or Section 1107.1.7.

    (3) The refrigerant detector as installed, including any sampling tubes, shall activate responses within a time not to exceed 30 seconds after exposure to refriger

    ant concentration exceeding the set point value specified in Section 1106.2.5 or Section 1107.1.7.

    1106.2.7 Mechanical Ventilation. Machinery rooms shall be vented to the outdoors, utilizing mechanical ventilation in accordance with Section 1106.2.8 and Section

    1106.2.9.

    1106.2.8 Ventilation. Mechanical ventilation referred

    to in Section 1106.2.7 shall be by one or more powerdriven fans capable of exhausting air from the machinery room at not less than the amount shown in accordance

    with Section 1106.2.9.

    To obtain a reduced airflow for normal ventilation, multiple fans or multispeed fans shall be used. Provision shall be made to supply makeup air to replace that being exhausted. Ducts for supply and exhaust to the machinery room shall serve no other area. The makeup air supply locations shall be positioned relative to the exhaust air locations to avoid short-circuiting. Inlets to the exhaust ducts shall be located in an area where refrigerant from a leak will concentrate, in consideration of the location of the replacement supply air paths, refrigerating machines, and the density of the refrigerant relative to air.

    Inlets to exhaust ducts shall be within 1 foot (305 mm) of the lowest point of the machinery room for refrigerants that are heavier than air, and shall be within 1 foot (305 mm) of the highest point for refrigerants that are lighter than air. The discharge of the exhaust air shall be to the outdoors in such a manner as not to cause a nuisance or danger.

    1106.2.9 Emergency Ventilation-Required Air- flow. An emergency ventilation system shall be required to exhaust an accumulation of refrigerant due to leaks or a rupture of the system. The emergency ventilation required shall be capable of removing air from the machinery room in not less than the airflow quantity in Section 1106.2.9.1. Where multiple refrigerants are present, then the highest airflow quantity shall apply.

  • CMC § 8.13.6.2 High relevance — show source text

    (1) Refrigerant compressors

    (2) Refrigerant pumps

    (3) Normally closed automatic refrigerant valves

    (4) Other unclassified electrical sources of ignition with apparent power rating greater than 1 kVA, where the apparent power is the product of the circuit voltage and current rating. [ASHRAE 15:8.13.6.2] 1106.11.7 Mechanical Equipment Control. Remote control of the mechanical equipment in the refrigerating machinery room shall be provided immediately outside the machinery room door solely for the purpose of shutting down the equipment in an emergency. Ventilation fans shall be on a separate electrical circuit and have a control switch located immediately outside the machinery room door. [ASHRAE 15:8.13.7] 1106.11.8 Refrigerant Detectors. Each refrigerating machinery room in accordance with Section 1106.11 shall contain one or more refrigerant detectors in accordance with Section 1106.11.9. The detector(s) sensing element shall be located in areas where refrigerant from a leak will concentrate, with one or more set points that activate responses in accordance with Section 1106.11.10 for alarms and Section 1106.11.11 for mechanical ventilation. Multiport-type devices shall be prohibited. {ASHRAE 15:8.13.8} 1106.11.9 Refrigerant Detectors Requirements. Refrigerant detectors required by Section 1106.11 shall meet all of the following conditions:

    (1) A refrigerant detector shall be capable of detecting each of the specific refrigerant designations in the machinery room.

    (2) The refrigerant detector shall activate responses within a time not to exceed a limit specified in Section 1106.11.10 and Section 1106.11.11 after exposure to refrigerant concentration exceeding a limit value specified in Section 1106.11.10 and Section 1106.11.11.

    (3) The refrigerant detector shall have a set point not greater than the applicable Occupational Exposure Limit (OEL) value in accordance with Table 1102.3. The applicable OEL value shall be the lowest OEL value for any refrigerant designation in the machinery room. For refrigerants that do not have an OEL value in Table 1102.3, use a value determined in accordance with the OEL as defined by ASHRAE 34 where approved by the Authority Having Jurisdiction.

    (4) The refrigerant detector shall have a set point not more than the applicable Refrigerant Concentration Limit (RCL) value in accordance with Table 1102.3. The applicable RCL value shall be the lowest RCL value for any refrigerant designation in the machinery room. For refrigerants that do not have a RCL value in Table 1102.3, use a value determined in accordance with the RCL as defined by ASHRAE 34 where approved by the Authority Having Jurisdiction.

    (5) The refrigerant detector shall provide a means for automatic self-testing and shall be in accordance with Section 1106.11.10.4. The refrigerant detector shall be tested during installation and annually thereafter in accordance with the fire code, or at an interval not exceeding the manufacturer’s installation instructions, whichever is less. Testing shall verify compliance with the alarm set points and response times per Section 1106.11.10 and Section 1106.11.11. [ASHRAE 15:8.13.9]

  • CMC § 1102.3. High relevance — show source text

    (3) The refrigerant detector shall have a set point not greater than the applicable Occupational Exposure Limit (OEL) value in accordance with Table 1102.3. The applicable OEL value shall be the lowest OEL value for any refrigerant designation in the machinery room. For refrigerants that do not have an OEL value in Table 1102.3, use a value determined in accordance with the OEL as defined by ASHRAE 34 where approved by the Authority Having Jurisdiction.

    (4) The refrigerant detector shall have a set point not more than the applicable Refrigerant Concentration Limit (RCL) value in accordance with Table 1102.3. The applicable RCL value shall be the lowest RCL value for any refrigerant designation in the machinery room. For refrigerants that do not have a RCL value in Table 1102.3, use a value determined in accordance with the RCL as defined by ASHRAE 34 where approved by the Authority Having Jurisdiction.

    (5) The refrigerant detector shall provide a means for automatic self-testing and shall be in accordance with Section 1106.11.10.4. The refrigerant detector shall be tested during installation and annually thereafter in accordance with the fire code, or at an interval not exceeding the manufacturer’s installation instructions, whichever is less. Testing shall verify compliance with the alarm set points and response times per Section 1106.11.10 and Section 1106.11.11. [ASHRAE 15:8.13.9]

    1106.11.10 Alarms. Alarms required by Section 1106.11.8 shall comply with Section 1106.11.10.1 through Section 1106.11.10.4.

    1106.11.10.1 Visual and Audio. The alarm shall

    have visual and audible annunciation inside the refrigerating machinery room and outside each entrance to the refrigerating machinery room.

    [ASHRAE 15:8.13.10.1] 1106.11.10.2 Detector Activation. The refrigerant detector set points shall activate an alarm in accordance with the type of reset in Table 1106.11.10.2. Manual reset type alarms shall have the reset located inside the refrigerating machinery room. [ASHRAE 15:8.13.10.2]

    TABLE 1106.11.10.2 REFRIGERANT DETECTOR SET POINTS, RESPONSE TIMES, ALARMS, AND VENTILATION LEVELS

    [ASHRAE 15: TABLE 8-1]

    LIMIT VALUE RESPONSE TIME
    (seconds)    		 ALARM TYPE ALARM RESET TYPE VENTILATION RATE VENTILATION
    RESET TYPE
    Set point≤ OEL ≤300 Trouble Alarm Automatic Level 1 Automatic
    Set point≤ RCL ≤15 Emergency Alarm Manual Level 2 Manual

    2025 CALIFORNIA MECHANICAL CODE 235

    ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

    REFRIGERATION

    1106.11.10.3 Alarm Levels. Alarms set at levels

  • CMC § 1106.11.10.1 Medium relevance — show source text

    1106.11.10.1 Visual and Audio. The alarm shall

    have visual and audible annunciation inside the refrigerating machinery room and outside each entrance to the refrigerating machinery room.

    [ASHRAE 15:8.13.10.1] 1106.11.10.2 Detector Activation. The refrigerant detector set points shall activate an alarm in accordance with the type of reset in Table 1106.11.10.2. Manual reset type alarms shall have the reset located inside the refrigerating machinery room. [ASHRAE 15:8.13.10.2]

    TABLE 1106.11.10.2 REFRIGERANT DETECTOR SET POINTS, RESPONSE TIMES, ALARMS, AND VENTILATION LEVELS

    [ASHRAE 15: TABLE 8-1]

    LIMIT VALUE RESPONSE TIME
    (seconds)    		 ALARM TYPE ALARM RESET TYPE VENTILATION RATE VENTILATION
    RESET TYPE
    Set point≤ OEL ≤300 Trouble Alarm Automatic Level 1 Automatic
    Set point≤ RCL ≤15 Emergency Alarm Manual Level 2 Manual

    2025 CALIFORNIA MECHANICAL CODE 235

    ), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

    REFRIGERATION

    1106.11.10.3 Alarm Levels. Alarms set at levels

    other than Table 1106.11.10.2 (such as IDLH) and automatic reset alarms are permitted in addition to those required by Section 1106.11.10. The meaning of each alarm shall be clearly marked by signage near the annunciators. [ASHRAE 15:8.13.10.3]

    1106.11.10.4 Emergency. In the event of a failure during a refrigerant detector self-test in accordance with Section 1106.11.9(5), a trouble alarm signal shall be transmitted to an approved monitored location. [ASHRAE 15:8.13.10.4]

    1106.11.11 Mechanical Ventilation. Machinery rooms, in accordance with Section 1106.11, shall be vented to the outdoors, using mechanical ventilation in accordance with Section 1106.11.11.1, Section 1106.11.11.2, and Section 1106.11.11.3. [ASHRAE 15:8.13.11]

    1106.11.11.1 Mechanical Ventilation Require- ments. Mechanical ventilation referred to in Sec tion 1106.11.11 shall be in accordance with all of

    the following:

    (1) Include one or more power-driven fans capable of exhausting air from the machinery room; multispeed fans shall be permitted.

    (2) Electric motors driving fans shall not be placed inside ducts; fan rotating elements shall be nonferrous or non-sparking, or the casing shall consist of or be lined with such material.

    (3) Include provision to supply make-up air to replace that being exhausted; ducts for supply to and exhaust from the machinery room shall serve no other area; the makeup air supply locations shall be positioned relative to the exhaust air locations to avoid short circuiting.

  • California Mechanical Code Medium relevance — show source text


    81
    135
    172
    195
    217|2637
    1694
    1674
    1641
    1609
    1578|1350
    1100
    1079
    1045
    1018
    990|0
    107
    174
    220
    248
    273|3701
    2343
    2320
    2282
    2245
    2210|1900
    1520
    1498
    1460
    1425
    1390| |30|0
    2
    5
    10
    15
    20
    30|0
    33
    69
    91
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    149|1173
    826
    811
    788
    765
    743
    702|650
    535
    524
    507
    490
    473
    444|0
    42
    82
    107
    124
    139
    171|1548
    1072
    1055
    1028
    1002
    977
    929|855
    700
    688
    668
    648
    628
    594|0
    54
    96
    125
    143
    160
    195|1977
    1351
    1332
    1301
    1272
    1243
    1189|1060
    865
    851
    829
    807
    784
    745|0
    74
    127
    164
    187
    207
    246|3004
    2004
    1981
    1944
    1908
    1873
    1807|1550
    1310
    1289
    1254
    1220
    1185
    1130|0
    98
    164
    209
    237
    260
    305|4252
    2786
    2759
    2716
    2674
    2633
    2555|2170
    1800
    1775
    1733
    1692
    1650
    1585| |50|0
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    26
    65
    86
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    113
    141|1297
    975
    960
    935
    911
    888
    844|708
    615
    605
    589
    572
    556
    522|0
    33
    77
    101
    117
    131
    161|1730
    1276
    1259
    1230
    1203
    1176
    1125|952
    813
    798
    773
    747
    722
    670|0
    41
    90
    118
    136
    151
    183|2231
    1620
    1600
    1567
    1536
    1505
    1446|1195
    1010
    996
    972
    948
    924
    876|0

Frequently asked questions

Where exactly in a machinery room should detectors be mounted?

Place sensing elements “in areas where refrigerant from a leak will concentrate” — low near the floor for heavier‑than‑air refrigerants and near the ceiling for lighter‑than‑air refrigerants; inlets to exhaust or sampling tubes should be within 1 foot of the lowest or highest point as applicable. See § 1106.2.5 and the ventilation inlet placement rules in § 1106.2.8.

At what concentration must equipment be shut off?

Equipment must be automatically shut off when refrigerant concentration exceeds the detector’s upper detection limit or 25% of the LFL, whichever is lower, per § 608.9.1 and § 608.10.1 (California Fire Code).

Do detectors need to auto‑test?

Yes. Detectors must perform automatic self‑testing of sensors and provide a trouble signal if a failure is detected, per § 1106.2.6(1).

Are manual resets required?

Yes. The alarms required by § 1106.2.5 must be manual reset type with the reset located inside the refrigeration machinery room; additional automatic reset alarms may be used in addition.

Do A2L/B2L refrigerants have different detector timing?

Yes. Machinery rooms for Group A2L/B2L follow the 1106.11 requirements and Table 1106.11.10.2, which specify different response times and alarm/reset behavior (e.g., ≤300 s for OEL/trouble, ≤15 s for emergency/RCL).

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