CMC · California Mechanical Code
Which refrigerants are permitted and how are they classified?
The CMC requires using refrigerants listed in Table 1102.3 (or ASHRAE 34 when approved) and assigns each refrigerant a two‑part safety group (toxicity A/B and flammability 1/2/2L/3) via Table 1103.1.1. These groups (A1, A2L, A2, A3, B1, B2L, B2, B3) determine where and how a refrigerant may be used: for example, A3/B3 (highly flammable) are largely prohibited without AHJ approval, A2L has special rules for human‑comfort systems, and toxicity and LFL thresholds (400 ppm and 0.00625 lb/ft³) are the decision triggers.
Last reviewed: July 6, 2026
What the code requires
In plain English: the code requires that the refrigerant in a system must be a type listed in Table 1102.3 (or be classified under ASHRAE 34 where the Authority Having Jurisdiction approves) and that refrigerants be placed into distinct safety groups combining a toxicity class (A or B) and a flammability class (1, 2, 2L, or 3). See § 1102.3 for the listing requirement and § 1103.1 (and Table 1103.1.1) for how refrigerants are classified.
The single most important rule: Use only refrigerants listed in Table 1102.3 (or ASHRAE 34 where approved), and treat each refrigerant by its combined safety group (for example A1, A2L, B2, B3, etc.) when applying the rest of Chapter 11.
Requirements in detail
Key defined terms and thresholds (first-use emphasized)
- Refrigerant — chemical used for heat transfer in a refrigerating system.
- Refrigerant Safety Classifications — a two-part label: a letter (A or B) for toxicity and a number (1, 2, 2L, 3) for flammability. Table 1103.1.1 shows the recognized groups (A1, A2L, A2, A3, B1, B2L, B2, B3). § 1103.1.1 explains that each refrigerant is assigned to one group.
- Toxicity threshold (OEL) — 400 ppm is the cutoff between Class A (OEL ≥ 400 ppm) and Class B (OEL < 400 ppm).
- Flammability threshold (LFL) — 0.00625 lb/ft³ (≈ 0.10012 kg/m³ at test conditions) is the critical value used to distinguish some flammability classes (Class 2/2L vs Class 3). Class 2L also requires a maximum burning velocity of 3.9 in/s (10 cm/s) in the referenced test.
How classification is made (short)
- The code requires classification according to Table 1102.3 or ASHRAE 34 (when AHJ-approved). § 1103.1 and § 1103.1.1 explain that classification is the result of combining the toxicity class (A/B) and the flammability class (1, 2, 2L, 3).
- For refrigerant blends, the classification is based on the worst-case result after possible fractionation — the blend is classified according to its worst-case toxicity and flammability.
Decision table — safety groups and the control dimensions
| Safety group | Toxicity (OEL) | Flammability (LFL / other test) | Typical implications for use | Code Reference |
|---|---|---|---|---|
| A1 | OEL ≥ 400 ppm | No flame propagation (Class 1) | Considered lower toxicity + non‑flammable — broadest allowed use | § 1103.1 / Table 1103.1.1 |
| A2L | OEL ≥ 400 ppm | Lower flammability; LFL > 0.00625 lb/ft³ and low burning velocity (Class 2L) | Allowed for many applications with A2L-specific provisions (see § 1104.6) | § 1103.1 / Table 1103.1.1 / § 1104.6 |
| A2 | OEL ≥ 400 ppm | Flammable (Class 2) | More restrictive than A2L — limits on charge and location apply | § 1103.1 / Table 1103.1.1 |
| A3 | OEL ≥ 400 ppm | Highly flammable (Class 3) | Not permitted except where AHJ approves; limited exceptions exist | § 1103.1 / § 1103.3 / Table 1103.1.1 |
| B1 | OEL < 400 ppm | No flame propagation (Class 1) | Higher toxicity but non‑flammable — constrained by toxicity controls | § 1103.1 / Table 1103.1.1 |
| B2L | OEL < 400 ppm | Lower flammability (Class 2L) | Toxic + lower flammability — subject to machinery room and detection rules | § 1103.1 / Table 1103.1.1 / § 1106.11 |
| B2 | OEL < 400 ppm | Flammable (Class 2) | Significant restrictions for occupied spaces and charge limits | § 1103.1 / Table 1103.1.1 |
| B3 | OEL < 400 ppm | Highly flammable (Class 3) | Not permitted except where AHJ approves; same high limits as A3 | § 1103.1 / § 1103.3 / Table 1103.1.1 |
Notes: the numeric LFL and OEL thresholds above come from the code definitions for flammability and toxicity classes; see the definitions section for exact test conditions and limits.
Where the formal list of permitted refrigerants is found
- The code’s list of commonly used refrigerants is the table referenced in § 1102.3 (Table 1102.3). If a refrigerant is not listed there, the code allows using the ASHRAE 34 designation only with AHJ approval. § 1102.3 is the controlling statement on which refrigerants are acceptable.
Relationship of Table 1103.1.1 to the rest of the chapter
- Table 1103.1.1 defines the safety groups used throughout Chapter 11. Systems, room-design, allowable quantities, venting, detectors, and machinery-room rules are applied based on the refrigerant group assigned in that table (see many references across Chapter 11, e.g., restrictions on A3/B3 in § 1103.3 and A2L human‑comfort provisions in § 1104.6).
Exceptions & special cases
- Use of ASHRAE 34: The code allows classification according to ASHRAE 34 where the Authority Having Jurisdiction (AHJ) approves; this can be used in lieu of Table 1102.3 classifications when accepted by the AHJ. § 1103.1.
- Higher‑flammability refrigerants (A3 / B3): Group A3 and B3 are not permitted except where approved by the AHJ. The code lists three common exceptions (laboratories with >100 sf/person, industrial occupancies, and listed self‑contained units containing ≤ 0.331 lb (0.150 kg) of Group A3) — see § 1103.3.
- Lithium bromide absorption systems: An express exception allows lithium bromide absorption systems that use water as the refrigerant (see § 1102.3 exception).
- Blends: Refrigerant blends are classified on their worst-case fractionation composition for toxicity and flammability — mixes that change the safety group may trigger the requirement to treat the system as new or to obtain AHJ approval.
Common mistakes
- Treating A2L the same as A2. A2L is a distinct group with lower burning velocity and different allowable uses; specific provisions for A2L human‑comfort systems exist in § 1104.6.
- Assuming all refrigerant blends behave like their largest component. The code requires worst-case fractionation classification for blends — don’t rely on nominal blend composition.
- Using A3/B3 refrigerants without AHJ approval or without checking the narrow exceptions in § 1103.3.
- Overlooking the listing requirement: the refrigerant must be a type listed in Table 1102.3 (or ASHRAE 34 where approved). Don’t assume an unlisted refrigerant is allowed. § 1102.3.
Worked example — classification and immediate consequence
Scenario: You are evaluating a refrigerant with measured properties of OEL = 300 ppm and LFL = 0.005 lb/ft³ (measured at the code test conditions).
Step 1 — Toxicity classification:
- OEL 300 ppm is less than the 400 ppm cutoff, so the refrigerant is Class B (higher toxicity).
Step 2 — Flammability classification:
- LFL 0.005 lb/ft³ is at or below the 0.00625 lb/ft³ threshold the code uses to indicate Class 3 (highly flammable), so the refrigerant is Class 3.
Result — Safety group:
- Combine the letter and number → B3. Under the code, Group B3 refrigerants are not permitted except where approved by the AHJ (see § 1103.3). That means you must obtain AHJ approval or use one of the narrow exceptions before installing in most occupancies.
(If instead the refrigerant had OEL ≥ 400 ppm and the same LFL, the result would be A3, which is similarly restricted.)
Related provisions (quick reference)
- § 1102.3 — Refrigerants must be a type listed in Table 1102.3 (or ASHRAE 34 where approved).
- § 1103.1 — Refrigerant classification requirement; use of Table 1102.3 or ASHRAE 34.
- Table 1103.1.1 — Refrigerant safety group classifications (lists the groups A1, A2L, … B3).
- § 1103.3 — Restrictions on Group A3 and B3 refrigerants and listed exceptions.
- § 1104.6 — Specific provisions for Group A2L refrigerants used for human comfort (sensors, listing, ventilation, nameplate/labeling).
- § 1104.9 — Rules for changing refrigerants in existing equipment (same-class vs different-class replacements).
- Table 1104.1 and § 1104.2 — System selection and refrigerant concentration limit (RCL) concepts used to convert RCLs into permissible charge amounts in a space.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 5.2.1 High 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 § 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).
44 2025 CALIFORNIA MECHANICAL CODE
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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 § 3.1 High relevance — show source text
Reclaimed Refrigerants. Refrigerants reprocessed to the same specifications as new refrigerants by any means, including distillation. Such refrigerants have been chemically analyzed to verify that those specifications have been met.
[ASHRAE 15:3]
Recovered Refrigerants. Refrigerants removed from a system in any condition without necessarily testing or processing them. [ASHRAE 15:3] Recycled Refrigerants. Refrigerants for which contaminants have been reduced by oil separation, removal of noncondensable gases, and single or multiple passes through filter driers or other devices that reduce moisture, acidity, and particulate matter. [ASHRAE 15:3] Refrigerant. A chemical compound intended to be used for heat transfer in a refrigerating system. Refrigerant Concentration Limit (RCL). The refrigerant concentration limit, in air, determined in accordance with this code and intended to reduce the risks of acute toxicity, asphyxiation, and flammability hazards in normally occupied, enclosed spaces. [ASHRAE 34:3.1] Refrigerant Designation. The unique identifying alphanumeric value assigned to an individual refrigerant. Refrigerant Safety Classifications. Made up of a letter (A or B), that indicates the toxicity class, followed by a number (1, 2, 2L, or 3), that indicates the flammability class. Refrigerant blends are similarly classified, based on the compositions at their worst cases of fractionation, as separately determined for toxicity and flammability. In some cases, the worst case of fractionation is the original formulation. 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).
44 2025 CALIFORNIA MECHANICAL CODE
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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.
CMC § 304.3. Medium relevance — show source text
(3) Cooling equipment, using Group A1 refrigerants or brine, located in an attic or furred space shall be permitted to be provided access by a minimum opening and passageway thereto of not less than 22 inches (559 mm) by 30 inches (762 mm).
(4) Cooling or refrigeration equipment, using Group A1 or B1 refrigerants or brine, located on a roof or on an exterior wall of a building, shall be permitted to be provided access as for furnaces in Section 304.3.
1105.4 Illumination and Service Receptacles. In addition to the requirements of Section 301.4, permanent luminaires shall be installed for equipment required by this code to be accessible or readily accessible. Such luminaires shall provide illumination to perform the required tasks for which access is provided. Control of the illumination source shall be provided at the access entrance.
Exceptions:
(1) Luminaires shall be permitted to be omitted where the fixed lighting of the building will provide the required illumination.
(2) Equipment located on the roof or on the exterior walls of a building.
1105.5 Ventilation of Rooms Containing Condensing Units. Where not in a refrigerant machinery room, rooms or spaces in which a refrigerant-containing portion of a condensing unit is installed shall be provided with ventilation in accordance with Section 1105.5.1 or Section 1105.5.2. Ventilation for machinery rooms shall comply with Section 1106.0.
1105.5.1 Permanent Gravity Ventilation Open- ings. Permanent gravity ventilation openings of not less
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(2) The resulting mixture does not change the refrigerant safety group. [ASHRAE 15:7.5.1.7]
1104.9 Changing Refrigerants. Changes of refrigerant in an existing system to a refrigerant with a different refrigerant designation shall only be allowed where in accordance with Section 1104.9.1 through Section 1104.9.4. [ASHRAE 15:5.3]
1104.9.1 Approval. The change of refrigerant shall be approved by the owner. [ASHRAE 15:5.3.1] 1104.9.2 Procedures. The change of refrigerant shall be in accordance with one of the following:
(1) Written instructions of the original equipment manufacturer.
(2) An evaluation of the system by a registered design professional or by an approved nationally recognized testing laboratory that validates safety and suitability of the replacement refrigerant.
(3) Approval of the Authority Having Jurisdiction.
[ASHRAE 15:5.3.2]
1104.9.3 Replacement Refrigerant of Same Clas- sification. Where the replacement refrigerant is classified into the same safety group, requirements that were applicable to the existing system shall continue to apply.
[ASHRAE 15:5.3.3]
1104.9.4 Replacement Refrigerant of Different Classification. Where the replacement refrigerant is classified into a different safety group, the system shall comply with the requirements of this chapter for a new installation, and the change of refrigerant shall require Authority Having Jurisdiction approval. [ASHRAE 15:5.3.4]
1105.0 General Requirements.
CMC § 607.4.1 Medium relevance — show source text
607.4.1 Design standards. The design, fabrication and assembly of system components shall be suitable for the working pressures, temperatures and structural stresses to be encountered by the components.
607.4.2 Components in contact with heated oil. System components that come in contact with heated cooking oil shall be rated for the maximum operating temperatures expected in the system.
607.5 Tank venting. Normal and emergency venting shall be provided for cooking oil storage tanks.
607.5.1 Normal vents. Normal vents shall be located above the maximum normal liquid line, and shall have a minimum effective area not smaller than the largest filling or withdrawal connection. Normal vents shall be permitted to vent inside the building.
607.5.2 Emergency vents. Emergency relief vents shall be located above the maximum normal liquid line, and shall be in the form of a device or devices that will relieve excessive internal pressure caused by an exposure fire. For nonmetallic tanks, the emergency relief vent shall be allowed to be in the form of construction. Emergency vents shall be permitted to vent inside the building.
607.6 Heating of cooking oil. Electrical equipment used for heating cooking oil in cooking oil storage systems shall be listed to UL 499 and shall comply with the California Electrical Code . Use of electrical immersion heaters shall be prohibited in nonmetallic tanks.
607.7 Electrical equipment. Electrical equipment used for the operation of cooking oil storage systems shall comply with the Cali- fornia Electrical Code.
SECTION 608—MECHANICAL REFRIGERATION
[M] 608.1 Scope. Refrigeration systems shall be installed in accordance with the California Mechanical Code .
608.1.1 Refrigerants other than ammonia. Where a refrigerant other than ammonia is used, refrigeration systems and the buildings in which such systems are installed shall be in accordance with ASHRAE 15.
608.1.2 Ammonia refrigeration. Refrigeration systems using ammonia refrigerant and the buildings in which such systems are installed shall comply with IIAR 2 for system design; IIAR 6 for inspection, testing and maintenance; and IIAR 7 for operating procedures. Decommissioning of ammonia refrigeration systems shall comply with IIAR 8, and engineering practices for existing ammonia refrigeration systems shall be in accordance with IIAR 9.
608.2 Permits. An operational permit shall be obtained for refrigeration systems as set forth in Section 105.5.46.
[M] 608.3 Refrigerants. The use and purity of new, recovered and reclaimed refrigerants shall be in accordance with the California Mechanical Code .
[M] 608.4 Refrigerant classification. Refrigerants shall be classified in accordance with the California Mechanical Code .
[M] 608.5 Change in refrigerant type. A change in the type of refrigerant in a refrigeration system shall be in accordance with the California Mechanical Code .
608.6 Access. Access to 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 shall be provided for the fire department at all times as required by the fire code official.
CMC § 0.00625 Medium relevance — show source text
** 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. [ASHRAE 15:5.1.2] Double Indirect Open Spray System. A system in which the secondary substance for an indirect open spray system is heated or cooled by the secondary coolant circulated from a second enclosure. [ASHRAE 15:5.1.2.2] Indirect Closed System. A system in which a secondary coolant passes through a closed circuit in the air or other substance to be cooled or heated. [ASHRAE 15:5.1.2.3] Indirect Open Spray System. A system in which a secondary coolant is in direct contact with the air or other substance to be cooled or heated. [ASHRAE 15:5.1.2.1] Refrigeration System, Mechanical. A combination of interconnected refrigerant-containing parts constituting one closed refrigerant circuit in which a refrigerant is circulated for the purpose of extracting heat and in which a compressor(s) is/are used for compressing the refrigerant vapor.
Refrigeration System, Self-Contained. A complete factory-assembled and tested system that is shipped in one or more sections and has no refrigerant-containing parts that are joined in the field by other than companion or block valves.
Registered Design Professional. An individual who is registered or licensed by the laws of the state to perform such design work in the jurisdiction.
Relief Valve, Vacuum. A device which automatically opens or closes for relieving a vacuum with the system, depending on whether the vacuum is above or below a predetermined value.
Removable. Capable of being transferred to another location with a limited application of effort and tools. [NFPA 96:3.3.42]
Replacement Air. See Air, Makeup.
CMC § 1103.0 Medium relevance — show source text
where approved by the Authority Having Jurisdiction.
Exception: Lithium bromide absorption systems using water as the refrigerant.
1103.0 Classification.
1103.1 Classification of Refrigerants. Refrigerants shall be classified in accordance with Table 1102.3 or in accor dance with ASHRAE 34 where approved by the Authority Having Jurisdiction.
1103.1.1 Safety Group. Table 1102.3 classifies refrigerants by toxicity and flammability, and assigns safety groups using combinations of toxicity class and flammability class. For the purposes of this chapter, the refrigerant Groups A1, A2L, A2, A3, B1, B2L, B2, and B3 shall be considered to be individual and distinct safety groups, as shown in Table 1103.1.1. Each refrigerant is assigned into not more than one group.
TABLE 1103.1.1
REFRIGERANT SAFETY GROUP CLASSIFICATIONS
1103.2 Classification of Refrigeration Systems. Refrigeration systems shall be classified according to the degree of probability that a leakage of refrigerant will enter an occupancy-classified area in accordance with Section 1103.2.1 and Section 1103.2.2. [ASHRAE 15:5.2]
1103.2.1 High-Probability System. Systems in which the basic design, or the location of components, is such that a leakage of refrigerant from a failed connection, seal, or component will enter the occupied space shall be classified as high-probability systems. A typical high-probability system shall be one of the following:
(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.
CMC § 7.5.1.7 Medium relevance — show source text
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(2) The resulting mixture does not change the refrigerant safety group. [ASHRAE 15:7.5.1.7]
1104.9 Changing Refrigerants. Changes of refrigerant in an existing system to a refrigerant with a different refrigerant designation shall only be allowed where in accordance with Section 1104.9.1 through Section 1104.9.4. [ASHRAE 15:5.3]
1104.9.1 Approval. The change of refrigerant shall be approved by the owner. [ASHRAE 15:5.3.1] 1104.9.2 Procedures. The change of refrigerant shall be in accordance with one of the following:
(1) Written instructions of the original equipment manufacturer.
(2) An evaluation of the system by a registered design professional or by an approved nationally recognized testing laboratory that validates safety and suitability of the replacement refrigerant.
(3) Approval of the Authority Having Jurisdiction.
[ASHRAE 15:5.3.2]
1104.9.3 Replacement Refrigerant of Same Clas- sification. Where the replacement refrigerant is classified into the same safety group, requirements that were applicable to the existing system shall continue to apply.
[ASHRAE 15:5.3.3]
1104.9.4 Replacement Refrigerant of Different Classification. Where the replacement refrigerant is classified into a different safety group, the system shall comply with the requirements of this chapter for a new installation, and the change of refrigerant shall require Authority Having Jurisdiction approval. [ASHRAE 15:5.3.4]
1105.0 General Requirements.
1105.1 Human Comfort. Cooling systems used for human comfort shall be in accordance with the return-air and outside-air provisions for furnaces in Section 604.1 and Section 904.8. Cooling equipment used for human comfort in residential buildings shall be selected in accordance with ACCA Manual S to satisfy the calculated loads determined in accordance with ACCA Manual J or other approved methods. Refrigerants used for human comfort shall be in accordance with Section 1104.7.
1105.2 Supports and Anchorage. Supports and anchorage for refrigeration equipment and piping shall be designed in accordance with the building code as Occupancy Category H (hazardous facilities). Supports shall be made of noncombustible materials.
Exceptions:
(1) Equipment containing Group A1 refrigerants shall be permitted to be supported by the same materials permitted for the building type.
(2) The use of approved vibration isolators specifically designed for the normal, wind, and seismic loads encountered, shall be permitted.
2025 CALIFORNIA MECHANICAL CODE 231
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REFRIGERATION
than 2 square feet (0.2 m [2] ) net free area opening shall be terminated directly to the outside of the building or extend to the outside of the building by continuous ducts.
1105.5.2 Mechanical Exhaust System. A mechanical exhaust system shall be designed to provide a complete change of air not less than every 20 minutes in such room or space and shall discharge to the outside of the building.
Exceptions:
CMC § 1101.0 Medium relevance — show source text
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CHAPTER 11
REFRIGERATION
1101.0 General.
1101.1 Applicability. Part I governs the design, installation, and construction of refrigeration systems, equipment, refrigerant piping, pressure vessels, safety devices, replacement of parts, alterations, and substitution of different refrigerants. Part II governs the installation and construction of cooling
towers.
1101.2 Equipment. Equipment for refrigerant recovery, recycling, or both shall comply with UL 1963.
Part I – Refrigeration Systems.
1102.0 Refrigeration Systems.
1102.1 General. Refrigeration systems using a refrigerant other than ammonia shall comply with this chapter and ASHRAE 15. Refrigeration systems containing carbon dioxide as the refrigerant shall also comply with IIAR CO2.
1102.2 Ammonia Refrigeration Systems. Refrigeration systems using ammonia as the refrigerant shall comply with IIAR 2, IIAR 3, IIAR/ANSI 4, IIAR 5, and IIAR 6 and shall not be required to comply with this chapter.
1102.3 Refrigerants. The refrigerant used shall be of a type listed in Table 1102.3 or in accordance with ASHRAE 34
where approved by the Authority Having Jurisdiction.
Exception: Lithium bromide absorption systems using water as the refrigerant.
1103.0 Classification.
1103.1 Classification of Refrigerants. Refrigerants shall be classified in accordance with Table 1102.3 or in accor dance with ASHRAE 34 where approved by the Authority Having Jurisdiction.
1103.1.1 Safety Group. Table 1102.3 classifies refrigerants by toxicity and flammability, and assigns safety groups using combinations of toxicity class and flammability class. For the purposes of this chapter, the refrigerant Groups A1, A2L, A2, A3, B1, B2L, B2, and B3 shall be considered to be individual and distinct safety groups, as shown in Table 1103.1.1. Each refrigerant is assigned into not more than one group.
TABLE 1103.1.1
REFRIGERANT SAFETY GROUP CLASSIFICATIONS
1103.2 Classification of Refrigeration Systems. Refrigeration systems shall be classified according to the degree of probability that a leakage of refrigerant will enter an occupancy-classified area in accordance with Section 1103.2.1 and Section 1103.2.2. [ASHRAE 15:5.2]
1103.2.1 High-Probability System. Systems in which the basic design, or the location of components, is such that a leakage of refrigerant from a failed connection, seal, or component will enter the occupied space shall be classified as high-probability systems. A typical high-probability system shall be one of the following:
(1) A direct system
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 § 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
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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
CMC § 608.1 Medium relevance — show source text
SECTION 608—MECHANICAL REFRIGERATION
[M] 608.1 Scope. Refrigeration systems shall be installed in accordance with the California Mechanical Code .
608.1.1 Refrigerants other than ammonia. Where a refrigerant other than ammonia is used, refrigeration systems and the buildings in which such systems are installed shall be in accordance with ASHRAE 15.
608.1.2 Ammonia refrigeration. Refrigeration systems using ammonia refrigerant and the buildings in which such systems are installed shall comply with IIAR 2 for system design; IIAR 6 for inspection, testing and maintenance; and IIAR 7 for operating procedures. Decommissioning of ammonia refrigeration systems shall comply with IIAR 8, and engineering practices for existing ammonia refrigeration systems shall be in accordance with IIAR 9.
608.2 Permits. An operational permit shall be obtained for refrigeration systems as set forth in Section 105.5.46.
[M] 608.3 Refrigerants. The use and purity of new, recovered and reclaimed refrigerants shall be in accordance with the California Mechanical Code .
[M] 608.4 Refrigerant classification. Refrigerants shall be classified in accordance with the California Mechanical Code .
[M] 608.5 Change in refrigerant type. A change in the type of refrigerant in a refrigeration system shall be in accordance with the California Mechanical Code .
608.6 Access. Access to 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 shall be provided for the fire department at all times as required by the fire code official.
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.
6-10 2025 CALIFORNIA FIRE CODE
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BUILDING SERVICES AND SYSTEMS
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.
- Treatment and flaring systems.
- Valves and appurtenances necessary to the operation of emergency refrigeration control boxes.
- Fans and associated equipment intended to operate emergency ventilation systems.
- 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.
Frequently asked questions
Can I use any new refrigerant if it meets manufacturer specs?
Only if the refrigerant is a type listed in Table 1102.3 or is classified by ASHRAE 34 with AHJ approval. The equipment manufacturer’s specified refrigerant and purity also apply (see § 1102.3 and equipment‑manufacturer requirements).
What is the difference between A2 and A2L?
Both are Class A (OEL ≥ 400 ppm) flammable groups, but A2L refrigerants have lower burning velocity and are tested to meet the 2L criteria (including the 3.9 in/s burning‑velocity limit). A2L systems have separate provisions (see § 1104.6).
Are blends treated differently than pure refrigerants?
Yes — blends are classified based on their worst‑case fractionation composition for both toxicity and flammability; the safety group must reflect that worst case.
Are highly flammable refrigerants (A3/B3) ever allowed?
They are generally prohibited unless the Authority Having Jurisdiction approves. There are limited exceptions (laboratories >100 sf/person, industrial occupancies, and certain listed self‑contained units ≤ 0.331 lb of A3). See § 1103.3.
If I change to a refrigerant of a different safety group, what then?
Changing to a refrigerant with a different safety group means the installation must comply with the chapter’s requirements for a new installation and requires AHJ approval (see § 1104.9.4).
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