CMC · California Mechanical Code
What identification, labeling and nameplate requirements apply for systems using flammable refrigerants?
If your HVAC or refrigeration equipment uses a flammable refrigerant, the California Mechanical Code requires the equipment be listed and carry a manufacturer-specified symbol on its nameplate, labels at service ports, and permanent vessel and machinery-room signs when sizes or horsepower trigger those rules — see §§ 1104.6.2, 1104.6.2.1 and 1115.0 for the exact requirements.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Refrigeration equipment that uses flammable refrigerants must be listed, installed per the listing/manufacturer instructions, and carry visible markings that identify the use of a flammable refrigerant — including a symbol on the equipment nameplate and labels at service locations. The controlling rules are § 1104.6.2 (listing/installation requirement), § 1104.6.2.1 (nameplate symbol requirement), and § 1115.0 (labeling and identification, including nameplate and permanent sign requirements) .
The single most important rule: equipment using a flammable refrigerant must be listed and carry a nameplate or label that clearly identifies the refrigerant as flammable so service personnel and authorities know the hazard and can follow the listed installation/servicing requirements.
Requirements in detail
1) Listing and installation — what’s the baseline
- The equipment must be listed and installed in accordance with its listing, the manufacturer's instructions, and any markings on the equipment. This is the primary performance requirement in § 1104.6.2 .
- Practical effect: follow the product listing (including any required labels, symbols, or location limitations) and the manufacturer's installation and servicing instructions.
2) Nameplate content and symbol (what must appear on the unit)
- A nameplate is required for each self-contained system or separate condensing/compressor unit (see § 1115.5). For systems using flammable refrigerants, the required nameplate must include a symbol indicating that a flammable refrigerant is used, as specified by the product listing (see § 1104.6.2.1 and § 1115.5) .
- The nameplate also carries the manufacturer identification, refrigerant designation (R‑number), and design pressures as required by § 1115.5 .
3) Service-port and component labeling (where to put warning labels)
- A label indicating a flammable refrigerant is used must be placed adjacent to service ports and other locations where service involving refrigerant-containing components is performed, as specified by the product listing (see § 1104.6.2.2) .
- The label requirement is intended to ensure field service technicians see the flammable-R notice at the point of access.
4) Machinery-room / permanent signs and vessel labels
- Equipment items (condenser, receiver, absorber, accumulator, etc.) with an internal volume greater than 3 cubic feet that contain refrigerant must have a permanent label indicating the type of refrigerant in the vessel (§ 1115.2) .
- For a refrigeration machinery room and for direct systems over 10 horsepower (7.5 kW), a permanent sign at an approved location must list: contractor name, refrigerant name/number, and pounds of refrigerant in the system (§ 1115.3) .
5) Related detection / mitigation actions required by listing
- If refrigerant detectors required by the listing sense concentrations above the setpoint, listed mitigation actions are required (e.g., supply fan operation, compressor shutdown) — see § 1104.6.2.4 and the surrounding requirements for refrigerant sensors and detection in § 1104.6.2.3 and § 1104.6.6 .
Quick decision table
| Item / decision factor | Required marking or action | Code Reference |
|---|---|---|
| Equipment must be listed and installed per listing/manufacturer | Follow listing & manufacturer instructions | § 1104.6.2 |
| Nameplate must show a flammable‑refrigerant symbol | Symbol on nameplate as specified by listing | § 1104.6.2.1 and § 1115.5 |
| Labels at service ports / service locations | Permanent label indicating flammable refrigerant adjacent to service ports | § 1104.6.2.2 |
| Vessel internal volume > 3 cu ft | Permanent label on vessel stating refrigerant type | § 1115.2 |
| Direct systems > 10 hp or machinery room | Permanent sign listing installer, refrigerant name/number, and pounds of refrigerant | § 1115.3 |
| Detector alarm actions | Follow listed mitigation (fan, shut down compressors, etc.) when detector setpoint exceeded | § 1104.6.2.4, § 1104.6.2.3 |
Practical label/nameplate content notes
- The code requires the symbol signifying flammability to match the product listing — do not substitute an unofficial marking. See § 1104.6.2.1 for the symbol requirement and § 1115.5 for the nameplate items .
- Labels must be permanent and located where they will be seen by servicing personnel (service ports, equipment access panels, vessel bodies, and in machinery rooms) per § 1104.6.2.2 and § 1115.2–1115.3 .
Exceptions & special cases
- The code includes an exception allowing compressors to remain running even when detectors sense gas above the setpoint if shutting the compressor would increase leak rate or the total amount of refrigerant released (see § 1104.6.2.4 — Exception) .
- Nameplate/symbol requirements are tied to the product listing. If a system is a listed self-contained unit with a manufacturer-applied nameplate, that factory-applied nameplate satisfies § 1115.5 when it contains the required information and symbol .
- For small self-contained units (equipment sold as factory sealed and listed for small charges), follow the product listing for marking/labeling specifics in lieu of additional field-applied labels if the listing specifies so (see § 1104.6.2) .
Common mistakes
- Assuming any flammable‑warning sticker is acceptable — the code requires the symbol and wording as specified by the product listing; generic stickers may not meet the listing and therefore may not be code‑compliant (see § 1104.6.2.1 & § 1104.6.2.2) .
- Forgetting to label vessels > 3 cu ft — receivers and large accumulators often require a permanent refrigerant‑type label under § 1115.2 .
- Not posting the machinery‑room permanent sign when required (direct system > 10 hp) or omitting the pounds of refrigerant on that sign — both are explicit requirements of § 1115.3 .
- Relying only on internal documentation — the code requires visible nameplates/labels on equipment and at service points (see § 1104.6.2.1, § 1104.6.2.2, § 1115.2–1115.3) .
Worked example — rooftop split system using an A2L refrigerant
Scenario:
- A commercial rooftop direct condensing unit is rated 15 hp and has a receiver with 4.5 cu ft internal volume. The unit uses an A2L (lower‑flammability) refrigerant and is a listed product.
How the code applies:
- Because this is a direct system > 10 hp, a permanent sign must be installed at an approved location for the machinery room (or equipment location) listing the installer, the refrigerant name/number, and the pounds of refrigerant in the system (§ 1115.3) .
- The condensing unit must carry a nameplate that includes the manufacturer name, refrigerant designation, and — because an A2L refrigerant is used — the symbol indicating a flammable refrigerant as specified by the product listing (§ 1104.6.2.1; § 1115.5) .
- The receiver has an internal volume > 3 cu ft, so the vessel must have a permanent label that states the type of refrigerant contained (§ 1115.2) .
- Labels indicating a flammable refrigerant must be placed adjacent to service ports and other service locations per § 1104.6.2.2; ensure the exact placement and label design meet the product listing requirements (§ 1104.6.2.2) .
- Ensure refrigerant detection and any listed mitigation steps (fans, compressor shutdown, etc.) are provided as required by the product listing and by § 1104.6.2.3–.4 if releasable charge/installation triggers those requirements .
In short: for this rooftop unit you must have the specified nameplate symbol, vessel label, service-port labels, machinery-room/permanent sign, and follow the listing’s required detection and mitigation measures.
Related provisions (other CMC sections to check)
- § 1104.6.2 — Listing and installation requirements for systems using A2L refrigerants
- § 1104.6.2.1 — Nameplate symbol requirement for flammable refrigerants
- § 1104.6.2.2 — Labeling at service ports and service locations for flammable refrigerants
- § 1104.6.2.3–.4 and § 1104.6.6 — Detection and required mitigation actions for refrigerant concentration alarms
- § 1115.0 – § 1115.5 — General labeling, vessel labels, permanent signs and nameplate content and requirements
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 1106.2.6. High relevance — show source text
(1) The space(s) containing the machinery is (are) separated from other occupancies by tight construction with tightfitting doors.
(2) Access is restricted to authorized personnel.
(3) Refrigerant detectors are installed with the sensing location and alarm level as required in refrigeration machinery rooms in accordance with Section 1106.2.6.
(4) Open flames and surfaces exceeding 800°F (427°C) shall not be permitted where a Group A2, B2, A3, or B3 refrigerant, is used.
(5) Electrical equipment that is in accordance with Class 1, Division 2, of NFPA 70 where the quantity of a Group A2, B2, A3, or B3 refrigerant in an independent circuit is capable of exceeding 25 percent of the lower flammability limit (LFL) upon release to the space based on the volume determined in accordance with Section 1104.2.1 through Section 1104.2.3.
(6) Refrigerant containing parts in systems exceeding 100 horsepower (74.6 kW) compressor drive power, except evaporators used for refrigeration or dehumidification, condensers used for heating, control and pressure-relief valves for either, low-probability pumps, and connecting piping, are located in a machinery room or outdoors.
[ASHRAE 15:7.2.2]
1104.5 Flammable Refrigerants. The total of Group A2, B2, A3, and B3 refrigerants, other than Group A2L and B2L refrigerants shall not exceed 1100 pounds (498.9 kg) without approval by the Authority Having Jurisdiction. Institutional Occupancies shall comply with Section 1104.3. Machinery rooms required in accordance with Section 1106.0 based on flammability shall be constructed and maintained in accordance with Section 1106.2.1 through Section 1106.2.6 and Section 1106.11 for Group A2L and B2L refrigerants. 1104.6 Group A2L Refrigerants for Human Comfort. High-probability systems using Group A2L refrigerants for human comfort applications shall comply with this section.
[ASHRAE 15:7.6]
1104.6.1 Refrigerant Concentration Limits. Occupied spaces shall comply with the releasable charge limitations of the equipment listing and ASHRAE 15. Unoccupied spaces with refrigerant containing equipment, not including continuous piping or tubing, shall comply with the releasable charge limitations of the equipment listing or Section 1104.6.4. {ASHRAE 15:7.6.1-7.6.1.2}
1104.6.2 Listing and Installation Requirements. Refrigeration systems shall be listed and shall be installed in accordance with listing, the manufacturer’s instructions, and any markings on the equipment restricting the installation. [ASHRAE 15:7.6.2]
1104.6.2.1 Nameplate. The nameplate required by Section 1115.5 shall include a symbol indicating that a flammable refrigerant is used, as specified by the product listing. [ASHRAE 15:7.6.2.1]
1104.6.2.2 Labeling. A label indicating a flammable refrigerant is used shall be placed adjacent to service ports and other locations where service involving components containing refrigerant is performed, as specified by the product listing.
CMC § 7.6 High relevance — show source text
[ASHRAE 15:7.6]
1104.6.1 Refrigerant Concentration Limits. Occupied spaces shall comply with the releasable charge limitations of the equipment listing and ASHRAE 15. Unoccupied spaces with refrigerant containing equipment, not including continuous piping or tubing, shall comply with the releasable charge limitations of the equipment listing or Section 1104.6.4. {ASHRAE 15:7.6.1-7.6.1.2}
1104.6.2 Listing and Installation Requirements. Refrigeration systems shall be listed and shall be installed in accordance with listing, the manufacturer’s instructions, and any markings on the equipment restricting the installation. [ASHRAE 15:7.6.2]
1104.6.2.1 Nameplate. The nameplate required by Section 1115.5 shall include a symbol indicating that a flammable refrigerant is used, as specified by the product listing. [ASHRAE 15:7.6.2.1]
1104.6.2.2 Labeling. A label indicating a flammable refrigerant is used shall be placed adjacent to service ports and other locations where service involving components containing refrigerant is performed, as specified by the product listing.
[ASHRAE 15:7.6.2.2]
1104.6.2.3 Refrigerant Detection Systems. Refrigerant detection systems shall be in accordance with the listing and ASHRAE 15.
2025 CALIFORNIA MECHANICAL CODE 229
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REFRIGERATION
1104.6.2.4 Refrigerant Concentration Above Limit. When the refrigerant detection system senses a refrigerant exceeding its setpoint, the following actions shall be taken:
(1) The supply air fan of the equipment shall activate with a minimum airflow rate specified by the manufacturer.
(2) Turn off the compressor and all other electrical devices, excluding the control power transformers, control systems, and the supply air fan. The supply air fan shall continue to operate for at least five minutes after the refrigerant detection system has sensed a drop in the refrigerant concentration below the value specified in Section 1104.6.6(b).
Exception: The compressor operation shall not be turned off when the compressor operation reduces the leak rate or the total amount of
released refrigerant to the indoor space.
(3) Any device that controls airflow located within the product or in ductwork that supplies air to the occupied space shall be fully open. Any device that controls airflow shall be listed.
CMC § 1115.4 High relevance — show source text
(1) Name of contractor installing the equipment.
(2) Name and number designation of refrigerant in system.
(3) Pounds of refrigerant in system.
1115.4 Marking of Pressure-Relief Devices. Pressurerelief valves for refrigerant containing components shall be set and sealed by the manufacturer or an assembler as defined in ASME BPVC Section VIII.1. Each pressure relief valve shall be marked by the manufacturer or assembler with the data required in ASME BPVC Section VIII.1.
Exception: Relief valves for systems with design pressures of 15 pounds-force per square inch gauge (psig) (103 kPa gauge) or less shall be marked by the manufacturer with the pressure setting capacity. [ASHRAE 15:9.6.1]
1115.4.1 Rupture Members. Rupture members for refrigerant pressure vessels shall be marked with the data required in accordance with ASME BPVC Section VIII.1. [ASHRAE 15:9.6.2]
1115.4.2 Fusible Plugs. Fusible plugs shall be marked with the melting temperatures in °F (°C).
[ASHRAE 15:9.6.3]
1115.5 Nameplate. Each self-contained system and each separate condensing unit, compressor, or compressor unit sold for field assembly in a refrigerating system shall carry a nameplate marked with the manufacturer’s name, nationally registered trademark or trade name, identification num
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REFRIGERATION
ber, design pressures, and refrigerant for which it is designed. The refrigerant shall be designated by the refrigerant number (“R-” number) as shown in Table 1102.3. {ASHRAE 15:9.15}
Heat pumps and electric cooling appliances shall bear a factory-applied nameplate in accordance with Section 307.3.
1116.0 Testing of Refrigeration Equipment.
1116.1 Factory Tests. Refrigerant-containing parts of unit systems shall be tested and proved tight by the manufacturer at not less than the design pressure for which they are rated. Pressure vessels shall be tested in accordance with Section
1117.0. [ASHRAE 15:9.14.1]
1116.1.1 Testing Procedure. Tests shall be performed with dry nitrogen or another nonflammable, nonreactive, dried gas. Oxygen, air, or mixtures containing them shall not be used. The means used to build up the test pressure shall have either a pressure limiting device or a pressure reducing device and a gauge on the outlet side. The pressure relief device shall be set above the test pressure but low enough to prevent permanent deformation of the system’s components.
Exceptions:
(1) Mixtures of dry nitrogen, inert gases, and Class 1 refrigerants shall be permitted for factory tests.
(2) Mixtures of dry nitrogen, inert gases, or a combination thereof with Class 2L, Class 2, or Class 3 refrigerants in concentrations not exceeding the lesser of a refrigerant weight fraction (mass fraction) of 5 percent or 25 percent of the LFL shall be permitted for factory tests.
CMC § 5703.2.1 High relevance — show source text
5703.2.1 Portable fire extinguishers and hose lines. Portable fire extinguishers shall be provided in accordance with Section 906. Hose lines shall be provided in accordance with Section 905.
5703.3 Site assessment. In the event of a spill, leak or discharge from a tank system, a site assessment shall be completed by the owner or operator of such tank system if the fire code official determines that a potential fire or explosion hazard exists. Such site assessments shall be conducted to ascertain potential fire hazards and shall be completed and submitted to the fire department within a time period established by the fire code official, not to exceed 60 days.
5703.4 Spill control and secondary containment. Where the maximum allowable quantity per control area is exceeded, and where required by Section 5004.2, rooms, buildings or areas used for storage, dispensing, use, mixing or handling of Class I, II and IIIA liquids shall be provided with spill control and secondary containment in accordance with Section 5004.2.
5703.4.1 Spill control and secondary containment for tanks in underground areas. Tanks in underground areas and associated piping systems shall be provided with spill control and secondary containment that are designed and constructed as outlined in Section 5004.2, except as modified by Section 5703.6.2.2.
5703.5 Labeling and signage. The fire code official is authorized to require warning signs for the purpose of identifying the hazards of storing or using flammable liquids. Signage for identification and warning such as for the inherent hazard of flammable liquids or smoking shall be provided in accordance with this chapter and Sections 5003.5 and 5003.6.
5703.5.1 Style. Warning signs shall be of a durable material. Signs warning of the hazard of flammable liquids shall have white lettering on a red background and shall read: “DANGER—FLAMMABLE LIQUIDS.” Letters shall be not less than 3 inches (76 mm) in height and [1] / 2 inch (12.7 mm) in stroke.
5703.5.2 Location. Signs shall be posted in locations as required by the fire code official. Piping containing flammable liquids shall be identified in accordance with ASME A13.1.
5703.5.3 Warning labels. Individual containers, packages and cartons shall be identified, marked, labeled and placarded in accordance with federal regulations and applicable state laws.
5703.5.4 Identification. Color coding or other approved identification means shall be provided on each loading and unloading riser for flammable or combustible liquids to identify the contents of the tank served by the riser.
5703.6 Piping systems. Piping systems, and their component parts, for flammable and combustible liquids shall be in accordance with Sections 5703.6.1 through 5703.6.11.
57-6 2025 CALIFORNIA FIRE CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLAMMABLE AND COMBUSTIBLE LIQUIDS
5703.6.1 Nonapplicability. The provisions of Section 5703.6 shall not apply to gas or oil well installations; piping that is integral to stationary or portable engines, including aircraft, watercraft and motor vehicles; and piping in connection with boilers and pressure vessels regulated by the California Mechanical Code .
CMC § 14.7 High relevance — show source text
Flammability Classification. Refrigerants shall be classified for flammability in accordance with one of the following: Class 1. Refrigerants that do not show flame propagation where tested in air at 14.7 pound-force per square inch absolute (psia) (101 kPa) and 140°F (60°C). Class 2. Refrigerants having a lower flammability limit (LFL) of more than 0.00625 pound per cubic foot (lb/ft [3] ) (0.10012 kg/m [3] ) at 140°F (60°C), 14.7 psia (101 kPa), and a heat of combustion of less than 8169 British thermal units per pound (Btu/lb) (1.8988 E+07 J/kg).
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DEFINITIONS
Class 2L. Refrigerants having a lower flammability limit (LFL) of more than 0.00625 pound per cubic foot (lb/ft [3] ) (0.10012 kg/m [3] ) at 140°F (60°C), 14.7 psia (101 kPa), a heat of combustion of less than 8169 British thermal units per pound (Btu/lb) (1.8988 E+07 J/kg), and a maximum burning velocity of 3.9 inches per second (10 cm/s) where tested at 73.4°F (23°C) and 14.7 psia (101 kPa) in dry air. Class 3. Refrigerants that are highly flammable having a LFL of not more than 0.00625 lb/ft [3] (0.10012 kg/m [3] ) at 140°F (60°C) and 14.7 psia (101 kPa) or a heat of combustion not less than 8169 Btu/lb (1.8988 E+07 J/kg). Toxicity Classification. Refrigerants shall be classified for the toxicity in accordance with one of the following: Class A. Refrigerants have an occupational exposure limit (OEL) of not less than 400 parts per million (ppm). Class B. Refrigerants have an OEL of less than 400
ppm. Refrigeration Machinery Room. A room designed to house compressors and refrigerant pressure vessels. Refrigeration Room or Space. A room or space in which an evaporator or brine coil is located for the purpose of reducing or controlling the temperature within the room or space to less than 68°F (20°C). Refrigeration System, Absorption. A heat-operated closed refrigeration cycle in which a secondary fluid, the absorbent, absorbs a primary fluid, the refrigerant that has been vaporized in the evaporator. Refrigeration System, Direct. A system in which the evaporator or condenser of the refrigerating system is in direct contact with the air or other substances to be cooled or heated.
[ASHRAE 15:5.1.1]
Refrigeration System, Indirect. A system in which a secondary coolant cooled or heated by the refrigerating system is circulated to the air or other substance to be cooled or heated. Indirect systems are distinguished by the method of application given below.
CMC § 1103.2 Medium relevance — show source text
1103.2 Classification of Refrigeration Systems . . . . . . . . . . . . . . . . . . . . 227
1103.3 Higher Flammability Refrigerants . . . . . . . . . . . . . . . . . 227
1104.0 Requirements for Refrigerant and Refrigeration System Use . . . 227
1104.1 System Selection . . . . . . . . . . . . . 227
1104.2 Refrigerant Concentration Limit (RCL) . . . . . . . . . . . . . . . . . . 227
Table 1104.1 Permissible Refrigeration Systems . . . . . . . . . . . . . . . . . . . . 228
1104.3 Institutional Occupancies . . . . . . . 229
1104.4 Industrial Occupancies and Refrigerated Rooms . . . . . . . . . . . 229
1104.5 Flammable Refrigerants . . . . . . . . 229
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TABLE OF CONTENTS
1104.6 Group A2L Refrigerants for Human Comfort . . . . . . . . . . . . . . 229
110.4.7 Applications for Human Comfort and for Nonindustrial
Occupancies. . . . . . . . . . . . . . . . . 230
1104.8 Refrigerant Type and Purity . . . . . 230
1104.9 Changing Refrigerants . . . . . . . . . 231
1105.0 General Requirements . . . . . . . . . 231
1105.1 Human Comfort . . . . . . . . . . . . . . 231
1105.2 Supports and Anchorage . . . . . . . 231
1105.3 Access . . . . . . . . . . . . . . . . . . . . . 231
1105.4 Illumination and Service
Receptacles . . . . . . . . . . . . . . . . . 231
1105.5 Ventilation of Rooms
Containing Condensing Units . . . . 231
1105.6 Prohibited Locations . . . . . . . . . . . 232
1105.7 Condensate . . . . . . . . . . . . . . . . . 232
1105.8 Defrost . . . . . . . . . . . . . . . . . . . . . 232
1105.9 Overflows . . . . . . . . . . . . . . . . . . . 232
1105.10 Condensate, Defrost, and Overflow Disposal. . . . . . . . . . . . . 232
1105.11 Refrigerant Port Protection . . . . . . 232
1105.12 Storage . . . . . . . . . . . . . . . . . . . . . 232
1106.0 Refrigeration Machinery Rooms . . 232
1106.1 Where Required . . . . . . . . . . . . . . 232
1106.2 Refrigeration Machinery Room, General Requirements . . . . . . . . . 232
CMC § 1125.0 Medium relevance — show source text
1125.0 Refrigerants and Hazardous Fluids.
1125.1 General. Equipment containing refrigerants as a part of a closed-cycle refrigeration system shall comply with Part I of this chapter. Equipment containing other fluids that are flammable, combustible, or hazardous shall be in accordance with this code and the fire code.
2025 CALIFORNIA MECHANICAL CODE 247
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REFRIGERATION
1126.0 Drift Eliminators.
1126.1 General. Cooling towers, evaporative condensers, and fluid coolers shall be equipped with drift eliminators that have a drift rate of not more than 0.005 percent of the circulated water flow rate in accordance with the equipment manufacturer’s instructions.
1127.0 Water Supply.
1127.1 General. Cooling towers, evaporative coolers and fluid coolers shall be provided with an approved water supply, sized for peak demand. The quality of water shall be provided in accordance with the equipment manufacturer’s recommendations. The piping system and protection of the potable water supply system shall be installed in accordance with the plumbing code.
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REFRIGERATION
TABLE 1102.3 REFRIGERANT GROUPS, PROPERTIES, AND ALLOWABLE QUANTITIES [7]
[ASHRAE 34: TABLE 4-1, TABLE 4-2]
REFRIGERANT CHEMICAL FORMULA CHEMICAL NAME1
(COMPOSITION FOR BLENDS)SAFETY
GROUPOEL2
(ppm)RCL (lb/Mcf) LFL8
(lb/Mcf)R-11 CCl3F Trichlorofluoromethane A1 1000 0.39 –– R-12 CCl2F2 Dichlorodifluoromethane A1 1000 5.6 –– R-12B1 CBrClF2 Bromochlorodifluoromethane –– –– –– –– R-13 CClF3 Chlorotrifluoromethane A1 1000 –– –– R-13B1 CBrF3 Bromotrifluoromethane A1 1000 –– –– R-13I1 CF3I Trifluoroiodomethane A1 500 1.0 –– R-14 CF4 Tetrafluoromethane (carbon tetrafluoride) A1 1000 25 –– R-21 CHCl2F Dichlorofluoromethane B1 –– –– –– R-22 CHClF2 Chlorodifluoromethane A1 1000 13 –– R-23 CHF3 Trifluoromethane A1 1000 7. CMC § 920.3 Medium relevance — show source text
Oil burning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .920.3
Ventilation of . . . . . . . . . . . . . . . . . . . . . . . . . . . . .504.3
RATPROOFING . . . . . . . . . . . . . . . . . . . . . . . . . . . . .316.10
RECIRCULATING SYSTEMS
Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220.0
Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .516.0
Labeling . . . . . . . . . . . . . . . . . . . . . . . .516.2.4, 516.2.5 Listing . . . . . . . . . . . . . . . . . . .516.2.2, 516.2.5, 516.2.9
Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .403.5
REFRIGERANTS
Ammonia . . . . . . . . . . . . . . . . . .1102.1, 1104.4, 1104.5,
1106.1.4, 1106.5, 1106.0, 1114.1,
Table 1102.3, Table E 503.7.1(7)
Amount of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1104.2
Applications for human comfort . . . . . . . . . . . . . .1104.7
Azeotrope, definition . . . . . . . . . . . . . . . . . . . . . . .203.0 Changing of . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1104.9
Classification of . . . . . . . . . . . . . . . . . . . . . . . . . .1103.0
Concentration limit . . . . . . . . . . . . . . . . . . . . . . . .1104.2
Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1109.0
Emergency purge . . . . . . . . . . . . . . . . . . . . . . . .1106.0
Flammable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1104.5
For human comfort . . . . . . . . . . . . . . . . .1104.7, 1104.8
In institutional occupancies . . . . . . . . . . . . . . . . .1104.3
In nonindustrial occupancies . . . . . . . . . . . . . . . .1104.7
CMC § 5.2.1 Medium relevance — show source text
(1) A direct system
(2) An indirect open spray system in which the refrigerant is capable of producing pressure that is more than the secondary coolant. [ASHRAE 15:5.2.1]
1103.2.2 Low-Probability System. Systems in which the basic design, or the location of the components, is such that a leakage of refrigerant from a failed connection, seal, or component cannot enter the occupied space shall be classified as low-probability systems. A typical low-probability system shall be one of the following:
(1) An indirect closed system
(2) Double indirect system
(3) An indirect open spray system. In a low-probability indirect open spray system, the secondary coolant pressure remains more than the refrigerant pressure in operating and standby conditions. [ASHRAE 15:5.2.2]
1103.3 Higher Flammability Refrigerants. Group A3 and B3 refrigerants shall not be used except where approved by the Authority Having Jurisdiction.
Exceptions:
(1) Laboratories with more than 100 square feet (9.29 m [2] ) of space per person.
(2) Industrial occupancies.
(3) Listed self-contained systems containing not more than 0.331 pounds (0.150 kg) of Group A3 refrigerant, provided that the equipment is installed in accordance with the listing and the manufacturer’s installation instructions. [ASHRAE 15:7.5.3]
1104.0 Requirements for Refrigerant and Refrigera- tion System Use.
1104.1 System Selection. Refrigeration systems shall be limited in application in accordance with Table 1104.1, and the requirements of Section 1104.0. 1104.2 Refrigerant Concentration Limit (RCL). The concentration of refrigerant in a complete discharge of an
Higher Flammability A3 B3 Flammable A2 B2 Lower Flammability A2L B2L No Flame Propagation
A1B1 Lower Toxicity Higher Toxicity 2025 CALIFORNIA MECHANICAL CODE 227
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REFRIGERATION
TABLE 1104.1 PERMISSIBLE REFRIGERATION SYSTEMS [1 ]
OCCUPANCY GROUP3 HIGH-PROBABILITY SYSTEM LOW PROBABILITY SYSTEM MACHINERY ROOM A-1 Group A1 or A2L4 only Any Any A-2 Group A1 or A2L4 only Any Any A-3 Group A1 or A2L4 only Any Any A-4 Group A1 or A2L4 only Any Any B Group A12 or A2L2,4 only Any Any E Group A1 or A2L4 only Any Any F-1 Group A12 or A2L2, CMC § 608.11.2.1 Medium relevance — show source text
608.11.2.1 Operation of an automatic crossover valve. Operation of an automatic crossover valve shall cause all compressors on the affected system to immediately stop. Dedicated pressure-sensing devices located immediately adjacent to crossover valves shall be permitted as a means for determining operation of a valve. To ensure that the automatic crossover valve system provides a redundant means of stopping compressors in an overpressure condition, high-pressure cutout sensors associated with compressors shall not be used as a basis for determining operation of a crossover valve.
608.11.2.2 Overpressure in low-pressure zone. The lowest pressure zone in a refrigeration system shall be provided with a dedicated means of determining a rise in system pressure to within 90 percent of the set point for emergency pressure relief devices. Activation of the overpressure sensing device shall cause all compressors on the affected system to immediately stop.
608.12 Storage, use and handling. Flammable and combustible materials shall not be stored in machinery rooms for refrigeration 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. Storage, use or handling of extra refrigerant or refrigerant oils shall be as required by Chapters 50, 53, 55 and 57.
Exception: This provision shall not apply to spare parts, tools and incidental materials necessary for the safe and proper operation and maintenance of the system.
2025 CALIFORNIA FIRE CODE 6-11
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
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BUILDING SERVICES AND SYSTEMS
608.13 Discharge and termination of pressure relief and purge systems. Pressure relief devices, fusible plugs and purge systems discharging to the atmosphere from refrigeration systems containing flammable, toxic or highly toxic refrigerants or ammonia shall comply with Sections 608.13.2 through 608.13.4.
608.13.1 Fusible plugs and rupture members. Discharge piping and devices connected to the discharge side of a fusible plug or rupture member shall have provisions to prevent plugging the pipe in the event the fusible plug or rupture member functions.
608.13.2 Flammable refrigerants. Systems containing more than 6.6 pounds (3 kg) of flammable refrigerants having a density equal to or greater than the density of air shall discharge vapor to the atmosphere only through an approved treatment system in accordance with Section 608.13.5 or a flaring system in accordance with Section 608.13.6. Systems containing more than 6.6 pounds (3 kg) of flammable refrigerants having a density less than the density of air shall be permitted to discharge vapor to the atmosphere provided that the point of discharge is located outside of the structure at not less than 15 feet (4572 mm) above the adjoining grade level and not less than 20 feet (6096 mm) from any window, ventilation opening or exit.
608.13.3 Toxic and highly toxic refrigerants. Systems containing more than 6.6 pounds (3 kg) of toxic or highly toxic refrigerants shall discharge vapor to the atmosphere only through an approved treatment system in accordance with Section 608.13.5 or a flaring system in accordance with Section 608.13.6.
CMC § 1013.7 Medium relevance — show source text
1013.7 Unfired Pressure Vessels . . . . . . . 221
1014.0 Operation and Maintenance of
Boilers and Pressure Vessels. . . . 221
1014.1 General. . . . . . . . . . . . . . . . . . . . . 221
Table 1003.2.1 Controls and Limit Devices for
Automatic Boilers . . . . . . . . . . . . . 222
CHAPTER 11 REFRIGERATION . . . . . . . . . . . . 225
1101.0 General. . . . . . . . . . . . . . . . . . . . . 227
1101.1 Applicability. . . . . . . . . . . . . . . . . . 227
1101.2 Equipment . . . . . . . . . . . . . . . . . . 227
Part I Refrigeration Systems . . . . . . . . 227
1102.0 Refrigeration Systems . . . . . . . . . 227
1102.1 General. . . . . . . . . . . . . . . . . . . . . 227
1102.2 Ammonia Refrigeration Systems . . 227
1102.3 Refrigerants . . . . . . . . . . . . . . . . . 227
1103.0 Classification . . . . . . . . . . . . . . . . 227
1103.1 Classification of Refrigerants . . . . 227
Table 1103.1.1 Refrigerant Safety Group Classifications. . . . . . . . . . . . . . . . 227
1103.2 Classification of Refrigeration Systems . . . . . . . . . . . . . . . . . . . . 227
1103.3 Higher Flammability Refrigerants . . . . . . . . . . . . . . . . . 227
1104.0 Requirements for Refrigerant and Refrigeration System Use . . . 227
1104.1 System Selection . . . . . . . . . . . . . 227
1104.2 Refrigerant Concentration Limit (RCL) . . . . . . . . . . . . . . . . . . 227
Table 1104.1 Permissible Refrigeration Systems . . . . . . . . . . . . . . . . . . . . 228
1104.3 Institutional Occupancies . . . . . . . 229
1104.4 Industrial Occupancies and Refrigerated Rooms . . . . . . . . . . . 229
1104.5 Flammable Refrigerants . . . . . . . . 229
2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
TABLE OF CONTENTS
1104.6 Group A2L Refrigerants for Human Comfort . . . . . . . . . . . . . . 229
110.4.7 Applications for Human Comfort and for Nonindustrial
Occupancies. . . . . . . . . . . . . . . . . 230
1104.8 Refrigerant Type and Purity . . . . . 230
1104.9 Changing Refrigerants . . . . . . . . . 231
CMC § 1102.3 Medium relevance — show source text
A major milestone reached in the industry was the introduction of lower flammability refrigerants such as A2L and B2L. The industry’s concerns to address lower Global Warming Potential (GWP) refrigerants led to the development of these lower flammability refrigerants. Chapter 11 does not only include these lower flammability refrigerants in Table 1102.3, but it also contains specific A2L and B2L provisions to address the precautions necessary for the proper use of these products. In particular, high-probability systems using A2L refrigerants for human comfort applications are covered by provisions which include refrigerant concentration limits, mechanical ventilation, ignition sources, compressors and pressure vessels, and refrigerant sensors.
In addition, Chapter 11 addresses other minimum requirements for refrigeration systems such as refrigeration machinery rooms (including ventilation), relief valves, and pressure vessels. Apart from refrigerants, the chapter also addresses minimum requirements for systems that use other mediums such as ammonia and brine systems. For ammonia systems, such systems are required to comply with IIAR 2, IIAR 3, IIAR/ANSI 4, IIAR 5, and IIAR 6.
Chapter 12 Hydronics. Chapter 12 regulates hydronic systems that are part of heating, cooling, ventilation, and conditioning systems. Such piping systems include steam, hot water, radiant heating and cooling, chilled water, steam condensate, condenser water, ground source heat pump systems, snow and ice melt systems, ambient temperature loops, and district ambient temperature loops. Provisions within this chapter addressing ground source heat pumps and ambient temperature loops apply to the hydronic portions of the system. Geothermal energy systems, including ground source heat pumps and ambient temperature loops, are regulated by Chapter 17.
Materials for piping and tubing must meet the working temperature and pressure of the system. In addition, materials must be compatible with the transfer medium to prevent deformation, bursting, or any chemical action between the material and the transfer medium. The allowable joining methods for piping or tubing are provided for application and enforcement purposes.
Chapter 13 Fuel Gas Piping. Chapter 13 regulates gas piping systems in a building, structure or within the property lines of buildings up to 5 psi. Gas piping systems must supply the minimum volume of gas required by each gas appliance to perform their proper operation under working conditions without exceeding the maximum pressure specified by each manufacturer. Because of the hazards associated with fuel gas, it is important to ensure the gas system has been inspected and tested, and that it is safe to turn on the gas supply to the building.
Chapter 14 Process Piping. Chapter 14 regulates process piping that typically is found in refineries. Process piping is considered the piping or tubing portion that transports liquid or gas, which is used directly in research, laboratory, or production process. This chapter may be used with another chapter of the code. For example, refrigeration piping, fuel gas piping, or fuel oil piping may need to comply with this chapter for process piping and the applicable chapter for materials, design, and installation.
Chapter 15 Solar Energy Systems. Chapter 15 refers the user to the Uniform Solar, Hydronics and Geothermal Code (USHGC) for solar energy system requirements. The USHGC contains comprehensive design, installation, and construction requirements for all types of solar thermal systems, such as drainback, thermosiphon, open-loop, and closed-loop systems. The USHGC also addresses installation of solar photovoltaic (PV) systems including array circuit(s), inverter(s), and controller(s) for such systems.
Frequently asked questions
Who decides the exact symbol and wording that must appear on the nameplate?
The product listing determines the symbol/wording; the code requires the nameplate to include the symbol “as specified by the product listing” (see § 1104.6.2.1) .
Do small factory‑sealed appliances need additional field labels?
Follow the product listing. If the factory-applied nameplate and listing satisfy the marking requirements, no extra field label is required; but labels at service ports may still be required per the listing and § 1104.6.2.2 .
What triggers the requirement for a permanent label on a vessel?
Any condenser, receiver, absorber, accumulator or similar equipment with an internal volume greater than 3 cubic feet containing refrigerant must carry a permanent label identifying the refrigerant type (§ 1115.2) .
Where must a permanent machinery‑room sign be posted?
A permanent sign must be posted in a machinery room and for direct systems over 10 horsepower at an approved location; it must list the installer, refrigerant name/number, and pounds of refrigerant (§ 1115.3) .
If a refrigerant detector alarms, does the code require immediate compressor shutdown?
Yes — listed mitigation actions are required when detectors sense refrigerant above the setpoint, typically including compressor shutdown and supply fan operation, unless the specific exception applies (see § 1104.6.2.4) .
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