CMC · California Mechanical Code
Refrigeration
Chapter 11 of the California Mechanical Code sets classification, quantity limits, machinery‑room, ventilation, detection, piping, and emergency control rules for refrigerants and refrigeration systems.
Last reviewed: July 6, 2026
Overview
Chapter 11 of the California Mechanical Code (CMC) governs the design, installation, and construction of refrigeration systems and equipment — including refrigerant piping, pressure vessels, safety devices, and cooling towers — and establishes when Part I (refrigeration systems) and Part II (cooling towers) apply, per §1101.1 . The chapter also references consensus standards for system design and equipment (for example, ASHRAE 15 and specific IIAR standards) so that refrigerant selection and system arrangements meet recognized safety and engineering practice as noted in §1102.1 and §1102.2 .
Refrigerants are classified by toxicity and flammability and assigned safety groups (Table 1102.3 and §1103.1) so charge limits, location rules, and equipment listings are applied correctly . The CMC includes explicit rules for lower‑flammability refrigerants (A2L/B2L), releasable charge limits, refrigeration machinery rooms, ventilation and detection requirements, and emergency controls — see §1104.6 for A2L provisions, §1106.1 for machinery‑room triggers, and §1108.3 for emergency shutoff controls .
This area of the code matters because refrigerants span toxic, flammable, and high‑pressure hazards; Chapter 11 ties refrigerant properties to installation criteria (classification, ventilation, storage, relief devices, piping materials, and alarms) so systems protect occupants, service personnel, and first responders while enabling modern low‑GWP refrigerant choices .
In this section
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 1108.4 High relevance — show source text
3_Exception_
1108.4
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Adopt Entire Chapter as
amended (amended sections
listed below)
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that are listed below
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1104.3_Exception_
1108.4
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amended (amended sections
listed below)
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that are listed below
Chapter/Section
1104.3_Exception_
1108.4
||||||||||||||||||||||||| |Adopting Agency
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amended (amended sections
listed below)
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that are listed below
Chapter/Section
1104.3_Exception_
1108.4
||||||||||X||||X||||||||||| |Adopting Agency
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amended (amended sections
listed below)
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that are listed below
Chapter/Section
1104.3_Exception_
1108.4
|||X||||||||||||||||||||||This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.
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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.
CMC § 1013.7 High 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 § 304.8 High relevance — show source text
For SI units: 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa
1112.12.5 Simultaneous Operation. When outlets of two or more relief devices or fusible plugs, which are
TABLE 1112.12.4
ATMOSPHERIC PRESSURE AT NOMINAL INSTALLATION ELEVATION ( Pa )
[ASHRAE 15: TABLE 9-2]
For SI units: 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa
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REFRIGERATION
1113.2 Type of Protection. Pressure vessels with an internal gross volume of 3 cubic feet (0.1 m [3] ) or less shall use one or more pressure relief devices or a fusible plug. Pressure vessels of more than 3 cubic feet (0.1 m [3] ) but less than 10 cubic feet (0.28 m [3] ) internal gross volume shall use one or more pressure relief devices. Fusible plugs shall not be used.
[ASHRAE 15:9.7.2.1, 9.7.2.2]
1113.3 Discharging into Lowside of System. For pressure-relief valves discharging into the lowside of the system, a single relief valve (not rupture member) of the required relieving capacity shall not be used on vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume except under the conditions permitted in Section 1112.11.3. [ASHRAE 15:9.7.3]
1113.4 Parallel Pressure-Relief Devices. Two or more
pressure-relief devices in parallel to obtain the required capacity shall be considered as one pressure-relief device. The discharge capacity shall be the sum of the capacities required for each pressure vessel being protected.
1113.5 Discharge Capacity. The minimum required discharge capacity of the pressure-relief device or fusible plug for a pressure vessel shall be determined in accordance with ASHRAE 15.
1113.6 Three-Way Valve. Pressure vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume shall use one or more rupture member(s) or dual pressure-relief valves where discharging to the atmosphere. Dual pressure-relief valves shall be installed with a three-way valve to allow testing or repair. Where dual relief valves are used, the valve shall comply with Section 1113.5.
Exception: A single relief valve shall be permitted on pressure vessels of 10 cubic feet (0.28 m [3] ) or more internal gross volume where in accordance with the following conditions:
(1) The relief valves are located on the lowside of the sys tem.
(2) The vessel is provided with shutoff valves designed to allow pumpdown of the refrigerant charge of the pressure vessel.
(3) Other pressure vessels in the system are separately protected in accordance with Section 1113.1. [ASHRAE 15:9.7.2.3]
1114.0 Special Discharge Requirements.
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 § 1105.10 Medium relevance — show source text
1105.10 Condensate, Defrost, and Overflow Dis- posal. Disposal of condensate, defrost, or overflow discharges shall comply with Section 310.0.
1105.11 Refrigerant Port Protection. Air conditioning refrigerant circuit access ports located outdoors shall be protected from unauthorized access with locking-type tamperresistant caps or in a manner approved by the Authority Having Jurisdiction.
Exception: Refrigerant ports in secure locations protected by walls or fencing and requiring key access.
1105.12 Storage. Refrigerants and refrigerant oils not charged within the refrigeration system shall be stored in accordance with Section 1105.12.1 and the fire code. Storage of materials in a refrigeration machinery room shall comply with the fire code.
1105.12.1 Storing Refrigerant. The total amount of refrigerant stored in a machinery room in all containers not provided with relief valves and piping in accordance with Section 1113.0 shall not exceed 330 pounds (149.7 kg). Refrigerant shall be stored in approved storage containers. Additional quantities of refrigerant shall be stored in an approved storage facility. [ASHRAE 15:11.5]
1106.0 Refrigeration Machinery Rooms.
1106.1 Where Required. Refrigeration systems shall be provided with a refrigeration machinery room where the conditions as outlined in Section 1106.1.1 through Section 1106.1.4 exist.
Exception: Refrigeration equipment shall be permitted to be located outdoors in accordance with ASHRAE 15.
1106.1.1 Quantity. The quantity of refrigerant in a single, independent refrigerant circuit of a system exceeds the amounts of Table 1102.3.
1106.1.2 Equipment. Direct- and indirect-fired absorption equipment is used.
Exception: Direct and indirect-fired lithium bromide absorption systems using water as the refrigerant.
1106.1.3 A1 System. An A1 system having an aggregate combined compressor horsepower of 100 (74.6 kW) or more is used.
1106.1.4 A1 Refrigerant. The system contains other than a Group A1 refrigerant.
Exceptions:
(1) Lithium bromide absorption systems using water as the refrigerant.
(2) Systems containing less than 300 pounds (136.1 kg) of refrigerant R-123 and located in an approved exterior location.
Refrigeration machinery rooms shall house refrigerant-containing portions of the system other than the piping and evaporators permitted by Section 1104.4, discharge piping required of this chapter, and cooling towers regulated by Part II of this chapter, and their essential piping.
1106.2 Refrigeration Machinery Room, General Requirements. Where a refrigeration system is located indoors and a machinery room is required in accordance with Section 1106.1, the machinery room shall be in accordance with Section 1106.2.1 through Section 1106.2.9.1.
1106.2.1 Access. Machinery rooms shall not be prohibited from housing other mechanical equipment unless specifically prohibited elsewhere in this chapter. A machinery room shall be so dimensioned that parts are accessible with space for service, maintenance, and operations. There shall be clear head room of not less than
7.25 feet (2210 mm) below equipment situated over passageways. [ASHRAE 15:8.11.1]
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.
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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.
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 § 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.
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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 § 1010.2 Medium relevance — show source text
1010.2 Power Boilers . . . . . . . . . . . . . . . . 220
1010.3 Steam-Heating Boilers, Hot Water Boilers, and Power Boilers. . 220
1010.4 Package Boilers, Steam-Heating Boilers, and Hot-Water-Heating Boilers. . . . . . . . . . . . . . . . . . . . . . 220
1011.0 Boilers, Stokers, and Steam
Generators . . . . . . . . . . . . . . . . . . 220
xxxviii
1011.1 General. . . . . . . . . . . . . . . . . . . . . 220
1012.0 Operating Adjustments and Instructions . . . . . . . . . . . . . . . . . . 220
1012.1 General. . . . . . . . . . . . . . . . . . . . . 220
1013.0 Inspections and Tests. . . . . . . . . . 220
1013.1 General. . . . . . . . . . . . . . . . . . . . . 220
1013.2 Operating Permit . . . . . . . . . . . . . 221
1013.3 Maintenance Inspection . . . . . . . . 221
1013.4 Power and Miniature Boilers. . . . . 221
1013.5 Steam-Heating and WaterHeating Boilers . . . . . . . . . . . . . . . 221
1013.6 Automatic Steam-Heating Boilers. . . . . . . . . . . . . . . . . . . . . . 221
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
CMC § 1106.11.11.4 Medium 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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REFRIGERATION
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 § 1107.1.10 Medium relevance — show source text
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.
1108.4 Installation, Maintenance, and Testing. Detection and alarm systems in accordance with Section 1106.2.5 shall be installed, maintained, and tested in accordance with the California Fire Code and with the equipment manufac- turer’s specification . 1108.5 Emergency Pressure Control System. Where required by the fire code, an emergency pressure control system shall be installed in accordance with applicable fire code requirements.
1109.0 Refrigeration Piping, Containers, and Valves.
1109.1 Materials. Materials used in the construction and installation of refrigerating systems shall be suitable for conveying the refrigerant used. Materials shall not be used that will deteriorate because of the refrigerant, the lubricant, or their combination in the presence of air or moisture to a degree that poses a safety hazard. [ASHRAE 15:9.1.1] Refrigerant piping shall be metallic. Materials for refrigerant piping, tubing, and fittings shall comply with the applicable standards in Table 1109.1.
2025 CALIFORNIA MECHANICAL CODE 237
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REFRIGERATION
For SI Units: 1 pound = 0.453 kg, 1 cubic foot per minute = 0.47194 L/s, 1 pound-force per square inch = 6.8947 kPa
FIGURE 1106.11.11.4
LEVEL 2 VENTILATION RATE FOR CLASS 2L REFRIGERANTS
[ASHRAE 15: FIGURE 8-1]
238 2025 CALIFORNIA MECHANICAL CODE
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REFRIGERATION
CMC § 8.13.6 Medium relevance — show source text
[ASHRAE 15:8.13.6]
»
(1) Operated, where occupied, to supply not less than 0.5 CFM/ft [2] [2.54 L/(s•m [2] )] of machinery room area or 20 cubic feet per minute (9.44 L/s) per person.
(2) Operable, where occupied at a volume required to not exceed the higher of a temperature rise of 18°F (10°C) above inlet air temperature or a maximum temperature of 122°F (50°C).
1106.4 Natural Ventilation. When a refrigerating system is located outdoors more than 20 feet (6096 mm) from building openings and is enclosed by a penthouse, lean-to, or other open structure, natural or mechanical ventilation shall be provided. The requirements for such natural ventilation shall be in accordance with the following:
(1) The free-aperture cross section for the ventilation of a machinery room shall be not less than as determined in accordance with Equation 1106.4.
F = √ G (Equation 1106.4)
Where:
F = The free opening area, ft [2] (m [2] ).
G = The mass of refrigerant in the largest system, any part of which is located in the machinery room, pounds.
For SI units: 1 square foot = 0.0929 m [2], 1 pound = 0.453 kg
(2) Locations of the gravity ventilation openings shall be based on the relative density of the refrigerant to air.
[ASHRAE 15:8.14]
1106.5 Combustion Air. No open flames that use combustion air from the machinery room shall be installed where refrigerant is used. Combustion equipment shall not be installed in the same machinery room with refrigerant-containing equipment except under one of the following conditions:
(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.
234 2025 CALIFORNIA MECHANICAL CODE
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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
Frequently asked questions
What code applies to ammonia refrigeration systems?
Refrigeration systems that use ammonia are required to comply with IIAR standards (IIAR 2, IIAR 3, IIAR/ANSI 4, IIAR 5, IIAR 6) and are not required to follow Chapter 11’s general provisions for other refrigerants, per §1102.2 .
Where are the A2L (lower‑flammability) rules for human‑comfort HVAC equipment?
Requirements for high‑probability systems and human‑comfort applications using Group A2L refrigerants are set out in §1104.6 (releasable charge limits, listing/installation, labeling, and related precautions) and are further connected to machinery‑room and ventilation rules in §1106 and §1107 .
When is a refrigeration machinery room required?
A dedicated refrigeration machinery room is required when thresholds such as the refrigerant quantity in a single circuit, use of certain equipment (e.g., direct‑fired absorption), aggregate compressor horsepower, or use of non‑A1 refrigerants are met — see §1106.1 for the specific triggers and exceptions .
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