CMC · California Mechanical Code

Sauna heaters, gaseous hydrogen and CNG fueling systems — applicable standards and installation

Q: Do I need a special mechanical permit to install a sauna heater?

Yes. The CMC requires sauna heaters to be listed to UL 875 and installed per the manufacturer; inspectors will expect listing documentation and that installation follows the instructions. See § 939.1 .

Q: Does the CMC give installation distances and ventilation rates for hydrogen or CNG systems?

No. The CMC requires that gaseous hydrogen systems follow NFPA 2 and that CNG fueling systems follow NFPA 52 ; the technical details (distances, ventilation rates, equipment capacities) are contained in those referenced standards and in the California Fire Code. See § 936.1 and § 937.1 .

Q: If my project involves hydrogen fueling, do I only follow the CMC?

No. The CMC directs you to NFPA 2 for hydrogen systems (see § 936.1 ), but hydrogen dispensing/quantities/siting/permits are also regulated in the California Fire Code and related chapters — you must comply with both.

For a homeowner: the California Mechanical Code doesn’t give every technical detail itself — it requires sauna heaters to be listed to UL 875 and installed per the manufacturer, requires hydrogen systems to be installed to NFPA 2, and requires CNG fueling systems to follow NFPA 52 and use appliances listed to the correct ANSI/CSA NGV standard. Always provide the appliance listing and the manufacturer’s installation instructions at permit review and coordinate with the Fire Code for siting and capacity limits.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Mechanical Code requires that sauna heaters be listed and installed to the applicable listing and the manufacturer’s instructions — specifically § 939.1 (electric sauna heaters) for sauna equipment. For gaseous hydrogen systems the CMC directs installation be in accordance with NFPA 2 (see § 936.0 / § 936.1). For CNG (compressed natural gas) vehicular fueling systems the CMC directs installation in accordance with NFPA 52 and requires residential and non‑residential fueling appliances to be listed to the appropriate ANSI/CSA NGV standard and installed per the manufacturer — see § 937.0 / § 937.1.

The single most important rule: follow the referenced standard and the appliance manufacturer — the CMC makes the standard and the manufacturer’s instructions the controlling installation requirements (see § 936.1, § 937.1, § 939.1).

Requirements in detail

How the CMC allocates responsibility

The CMC does not rewrite NFPA, ANSI/CSA or UL technical requirements; it mandates compliance with those referenced standards. See § 936.1, § 937.1, and § 939.1.
The CMC also requires that equipment be installed in accordance with the manufacturer’s installation instructions whenever a listing/standard is referenced. See § 939.1 (sauna heaters) and § 937.1 (CNG appliances).

Decision table — what standard to use and where to look

System / item	Required standard / listing	Installation authority / source	Code Reference
Gaseous hydrogen systems	Install in accordance with NFPA 2	NFPA 2 and manufacturer instructions	§ 936.0 / § 936.1
CNG vehicular fueling systems (general)	Install in accordance with NFPA 52	NFPA 52 and manufacturer instructions	§ 937.0 / § 937.1
Residential CNG fueling appliance (RFA)	Listed in accordance with ANSI/CSA NGV 5.1	Appliance listing and manufacturer instructions (see NFPA 52 for system-level requirements)	§ 937.1
Non‑residential CNG fueling appliance (VFA)	Listed in accordance with ANSI/CSA NGV 5.2	Appliance listing and manufacturer instructions (see NFPA 52)	§ 937.1
Electric sauna heaters	Listed in accordance with UL 875	Manufacturer’s installation instructions	§ 939.0 / § 939.1

Notes:

The CMC references the listed standard as the required installation standard; the code text itself contains only those references and the requirement to follow them. See the heading 936.0, 937.0, 939.0 and the General clauses that follow.

Installation checkpoints (what an inspector will verify)

Equipment is listed to the standard called out (UL 875 for sauna heaters; ANSI/CSA NGV 5.1 or 5.2 for CNG appliances). See § 939.1 and § 937.1.
System-level design and siting conform to the referenced NFPA standard (for hydrogen: NFPA 2 per § 936.1; for CNG: NFPA 52 per § 937.1).
Installation follows the appliance manufacturer’s instructions (explicitly required by the CMC for these appliances). See § 939.1, § 937.1.

Exceptions & special cases

The CMC text provided is brief and delegates technical detail to the referenced standards. The CMC sections do not list siting distances, ventilation rates, or appliance capacities themselves — those specifics are in the referenced documents (for example NFPA 2, NFPA 52, ANSI/CSA NGV standards and UL 875). See § 936.1, § 937.1, § 939.1.
Related California Fire Code provisions impose additional limits and operational requirements (for example, the Fire Code limits residential CNG appliance capacity and sets outdoor/indoor siting and operational rules). Those Fire Code limits are not restated in the CMC section, but they must be checked in parallel when designing or permitting a fueling installation (see California Fire Code §§ 2308.2.3–2308.2.4 and related sections).
Mobile or on‑demand hydrogen fueling operations and quantities are controlled by the California Fire Code (mobile fueling limits and permit requirements); the CMC requires NFPA 2 compliance but does not reproduce those mobile‑fueling limits. Check the Fire Code when the project involves dispensing.

Plain statement if something is missing:

The CMC sections located at § 936.0, § 937.0, and § 939.0 in the provided materials consist of short referencing requirements (mandating NFPA/UL/ANSI/CSA standards and manufacturer instructions). The CMC text shown does not include the technical minutiae (clearances, ventilation rates, electrical wiring details, or fuel‑flow capacities) — those are in the referenced standards and in the California Fire Code.

Common mistakes

Treating the CMC clause as a full technical spec instead of as a reference to NFPA/UL/ANSI/CSA standards (result: missing critical technical requirements). See § 936.1, § 937.1, § 939.1.
Installing an appliance that is not listed to the standard the CMC requires (e.g., a sauna heater not listed to UL 875). Check the listing on the unit and documentation. See § 939.1.
Ignoring the manufacturer’s installation instructions — the CMC explicitly requires following them wherever a listing/standard is invoked. See § 937.1 and § 939.1.
Failing to coordinate with the Fire Code for CNG and hydrogen siting, capacities and operating/permit requirements (CMC defers to NFPA; Fire Code adds jurisdictional requirements). See Fire Code references for CNG/hydrogen constraints.

Worked example — residential CNG fueling appliance (RFA)

Scenario: You plan to install a residential, permanently‑mounted CNG dispenser in a single‑family garage to fuel your family vehicle.

Step 1 — appliance selection: choose a unit that is listed to ANSI/CSA NGV 5.1 (residential fueling appliance listing). This listing requirement comes from § 937.1 of the CMC. Confirm the unit’s data plate and listing documentation.

Step 2 — check capacity (Fire Code cross‑check): the California Fire Code restricts an RFA capacity to no more than 5 cubic feet per minute (0.14 m3/min); a unit of 4.5 cfm would meet that Fire Code limit and therefore be a candidate RFA, while a 12 cfm unit would not and would be a non‑residential (VFA) device requiring ANSI/CSA NGV 5.2 listing and additional separation/siting controls. The CMC requires the correct listing (NGV 5.1 for residential) and NFPA 52 system compliance; the Fire Code provides the practical capacity limits you must observe.

Step 3 — installation: install per the appliance manufacturer’s instructions and NFPA 52 for system connections and venting. The CMC requires both the listing and that the installation be done per manufacturer instructions/NFPA 52 (see § 937.1).

Step 4 — permitting and coordination: submit listing documentation and manufacturer installation instructions with your permit application; coordinate any Fire Code siting or operational permits required for dispensing equipment. The CMC’s direction to NFPA 52 and the appliance listing will be primary in mechanical review; the Fire Code will govern quantities, separation and hazardous operations.

Related provisions (CMC sections)

§ 933.2 — Unit coolers (related appliance listing/installation approach).
§ 934.1 — Ductless mini‑split systems installation (example of “install per manufacturer” approach in the CMC).
§ 935.1 — Electrostatic air cleaners (another listed‑equipment requirement).
§ 938.1 — Dehumidifiers (listed standard + manufacturer instructions approach).
§ 939.0 / § 939.1 — Sauna heaters (UL 875; manufacturer instructions).
§ 936.0 / § 936.1 — Gaseous hydrogen systems (NFPA 2).
§ 937.0 / § 937.1 — CNG vehicular fuel systems (NFPA 52; ANSI/CSA NGV 5.1/5.2).

(For operational limits, siting distances, ventilation rates, and mobile fueling quantity limits also check the California Fire Code: see, e.g., Fire Code §§ 2308 and 2309 for CNG and hydrogen specifics.)

Code references

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

CMC § 936.0 High relevance — show source text

instructions.

936.0 Gaseous Hydrogen Systems.

936.1 General. Gaseous hydrogen systems shall be installed in accordance with NFPA 2.

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems.

937.1 General. The installation of compressed natural gas (CNG) fueling (dispensing) systems shall be in accordance with NFPA 52. Residential CNG fueling appliances shall be listed in accordance with ANSI/CSA NGV 5.1 and installed in accordance to the appliance manufacturer’s installation instructions. Non-residential CNG fueling appliances shall be listed in accordance with ANSI/CSA NGV 5.2 and installed in accordance with the appliance manufacturer’s installation instructions. [NFPA 54:10.27]

938.0 Dehumidifiers.

938.1 General. Dehumidifiers shall comply with UL 603352-40, and be installed in accordance with the manufacturer’s installation instructions.

939.0 Sauna Heaters.

939.1 Electric Sauna Heaters. Sauna heaters shall comply with UL 875 and shall be installed in accordance with the manufacturer’s installation instructions.

214 2025 CALIFORNIA MECHANICAL CODE

CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

CHAPTER 10 – BOILERS AND PRESSURE VESSELS

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	HCD	Col6	Col7	DSA	Col9	Col10	OSHPD	Col12	Col13	Col14	Col15	Col16	Col17	BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	6	6	6	6	6	6	6	6	6
Adopt Entire Chapter	X		X	X	X			X								X		X
Adopt Entire Chapter as amended (amended sections listed below)										X	X	X	X	X	X
Adopt only those sections that are listed below
Chapter/Section
1001.2.1										X	X	X	X	X	X

CMC § 933.2 High relevance — show source text
»

»»

» [»]

»

» [»]

»

»

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

INSTALLATION OF SPECIFIC APPLIANCES

933.2 Unit Coolers. Factory-built unit coolers for use in refrigerators, freezers, refrigerated warehouses, and walk-in coolers shall comply with UL 412 or UL 60335-2-89 and shall be installed in accordance with the manufacturer’s

installation instructions.

933.3 Self-Contained Mechanical Refrigeration Sys- tems. Self-contained mechanical refrigeration systems for use in walk-in coolers shall comply with UL 427 or UL 60335-2-89 and shall be installed in accordance with the man ufacturer’s installation instructions.

934.0 Ductless Mini-Split Systems Installation.

934.1 General. A ductless mini-split system installation shall be installed in accordance with the manufacturer’s

installation instructions and Section 310.2 for condensate

control.

935.0 Air Filter Appliances.

935.1 Electrostatic Air Cleaners. Electrostatic air cleaners shall comply with UL 867 and installed in accordance with the manufacturer’s installation instructions.

935.2 High-Efficiency Particulate Air Filter Units. High-efficiency particulate air filter units for use in industrial and laboratory exhaust and ventilation systems shall be installed in accordance with the manufacturer’s installation

instructions.

936.0 Gaseous Hydrogen Systems.

936.1 General. Gaseous hydrogen systems shall be installed in accordance with NFPA 2.

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems.

937.1 General. The installation of compressed natural gas (CNG) fueling (dispensing) systems shall be in accordance with NFPA 52. Residential CNG fueling appliances shall be listed in accordance with ANSI/CSA NGV 5.1 and installed in accordance to the appliance manufacturer’s installation instructions. Non-residential CNG fueling appliances shall be listed in accordance with ANSI/CSA NGV 5.2 and installed in accordance with the appliance manufacturer’s installation instructions. [NFPA 54:10.27]

938.0 Dehumidifiers.

938.1 General. Dehumidifiers shall comply with UL 603352-40, and be installed in accordance with the manufacturer’s installation instructions.

939.0 Sauna Heaters.

939.1 Electric Sauna Heaters. Sauna heaters shall comply with UL 875 and shall be installed in accordance with the manufacturer’s installation instructions.

214 2025 CALIFORNIA MECHANICAL CODE

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

CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE

CHAPTER 10 – BOILERS AND PRESSURE VESSELS

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
California Mechanical Code High relevance — show source text
**| |0;00||68||00||0||20||00||0| |0;05|1|000|2|330||39||538|1|290||22| |0:10|1|300|7|740||129||704|4|300||72| |0:15|1|399|14|150||236||760|7|860||131| |0:20|1|462|20|970||350||795|11|650||194| |0:25|1|510|28|050||468||821|15|590||260| |0:30|1|550|35|360||589||843|19|650||328| |0:35|1|584|42|860||714||862|23|810||397| |0:40|1|613|50|510||842||878|28|060||468| |0:45|1|638|58|300||971||892|32|390||540| |0:50|1|661|66|200|1|103||905|36|780||613| |0:55|1|681|74|220|1|237||916|41|230||687| |1:00|1|700|82|330|1|372||927|45|740||762| |1:05|1|718|90|540|1|509||937|50|300||838| |1:10|1|735|98|830|1|647||946|54|910||915| |1:15|1|750|107|200|1|787||955|59|560||993| |1:20|1|765|115|650|1|928||963|64|250||071| |1:25|1|779|124|180|2|070||971|68|990|1|150| |1:30|1|792|132|760|2|213||978|73|760|1|229| |1:35|1|804|141|42
CMC § 932.3 High relevance — show source text
932.3 Access, Inspection, and Repair. . . 213

932.4 Installation . . . . . . . . . . . . . . . . . . 213

933.0 Refrigeration Appliances . . . . . . . 213

933.1 Self-Contained Refrigerators and Freezers . . . . . . . . . . . . . . . . 213

933.2 Unit Coolers . . . . . . . . . . . . . . . . . 214

933.3 Self-Contained Mechanical

Refrigeration Systems . . . . . . . . . 214

934.0 Ductless Mini-Split Systems Installation . . . . . . . . . . . . . . . . . . 214

934.1 General. . . . . . . . . . . . . . . . . . . . . 214

935.0 Air Filter Appliances . . . . . . . . . . . 214

935.1 Electrostatic Air Cleaners . . . . . . . 214

935.2 High-Efficiency Particulate Air Filter Units . . . . . . . . . . . . . . . . 214

936.0 Gaseous Hydrogen Systems . . . . 214

936.1 General. . . . . . . . . . . . . . . . . . . . . 214

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems . . . . . . . . 214

937.1 General. . . . . . . . . . . . . . . . . . . . . 214

938.0 Dehumidifiers . . . . . . . . . . . . . . . . 214

938.1 General. . . . . . . . . . . . . . . . . . . . . 214

939.0 Sauna Heaters . . . . . . . . . . . . . . . 214

939.1 Electric Sauna Heaters. . . . . . . . . 214

CHAPTER 10 BOILERS AND

PRESSURE VESSELS . . . . . . . . 215

1001.0 General. . . . . . . . . . . . . . . . . . . . . 217

1001.1 Applicability. . . . . . . . . . . . . . . . . . 217

1001.2 Boiler Rooms and Enclosures . . . 217

1001.3 Air for Combustion

and Ventilation . . . . . . . . . . . . . . . 217

1001.4 Drainage . . . . . . . . . . . . . . . . . . . . 217

1001.5 Mounting. . . . . . . . . . . . . . . . . . . . 217

xxxvii

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

TABLE OF CONTENTS

1001.6 Chimneys or Vents . . . . . . . . . . . . 217

1002.0 Standards . . . . . . . . . . . . . . . . . . . 217

1002.1 General. . . . . . . . . . . . . . . . . . . . . 217
California Mechanical Code High relevance — show source text

50
83
99|780
483
473
463|415
322
313
303|0
60
99
117|1006
619
607
596|537
418
407
396|0
71
115
137|1261
770
758
746|660
515
503
490|0
98
154
180|1858
1124
1110
1097|970
745
733
720|0
130
199
231|2571
1543
1528
1514|1320
1020
1010
1000| |10|0
2
5
10|0
48
81
104|847
533
522
504|450
355
346
330|0
57
95
122|1096
684
671
651|585
457
446
427|0
68
112
142|1377
852
839
817|720
560
547
525|0
93
149
187|2036
1244
1229
1204|1060
850
829
795|0
124
192
238|2825
1713
1696
1669|1450
1130
1105
1080| |15|0
2
5
10
15|0
45
76
99
115|970
633
620
600
580|525
414
403
386
373|0
53
90
116
134|1263
815
800
777
755|682
544
529
507
491|0
63
105
135
155|1596
1019
1003
977
953|840
675
660
635
610|0
86
140
177
202|2380
1495
1476
1446
1418|1240
985
967
936
905|0
114
182
227
257|3323
2062
2041
2009
1976|1720
1350
1327
1289
1250| |20|0
2
5
10
15
20|0
41
73
95
111
125|1057
711
697
675
654
634|575
470
460
443
427
410|0
50
86
112
129
145|1384
917
902
877
853
830|752
612
599
576
557
537|0
CMC § 1220.4.2 Medium relevance — show source text
8|1220.4.2 – 1220.4.6| |1221.7|1221.6| |1308.2 – 1308.4.1|1308.3 – 1308.5.1| |Table 1308.3.1|Table 1308.4.1| |1308.4.2|1308.5.2| |1308.4.2.2 – 1308.6.4|1308.5.2.1 – 1308.7.3| |Table 1308.4.6.2|Table 1308.5.6.2| |1308.6.5 – 1308.13.1|1308.7.7 – 1308.14.1| |1312.1.2 – 1312.1.3|1312.1.1 – 1312.1.2| |Chapter 17|Appendix F| |Chapter 18|Chapter 17| |D 103.2|D 103.1| |E 503.5.6.7|E 503.5.6.6| |E 503.5.7.2 – E 503.5.7.6|E 503.5.7.1 – E 503.5.7.5| |Table E 503.5.7.2|Table E 503.5.7.1| |Table E 503.5.7.6|Table E 503.5.7.5| |Table E 503.5.10.1.2(1)|Table E 503.5.10(1)| |Table E 503.5.10.1.2(2)|Table E 503.5.10(2)| |E 503.5.10.1.2|E 503.5.10| |E 503.5.10.2 – E 503.5.10.2.2|E 503.5.10.1 – E 503.5.10.1.2| |E 503.5.12.1|E 503.5.12| |E 503.5.12.2|E 503.5.12.1| |E 503.6.5.4|E 503.6.5.4.1|

xxii 2025 CALIFORNIA MECHANICAL CODE

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

RELATED PUBLICATIONS AND SERVICES

The Documents Listed are Not by this Reference Adopted by The State of California.

IAPMO provides a variety of other products which are useful for inspectors, building officials, architects, engineers,

manufacturers, contractors, plumbers, and apprentices.

IAPMO Headquarters Directory

4755 East Philadelphia Street, Ontario, California 91761-2816

Publication Order Desk Phone: 800-85-IAPMO

Publication Toll Free Fax: 877-85-CODES

E-mail: iapmo@iapmo.org

Website: www.iapmo.org

Free Code Question: 800-201-0335

Uniform Mechanical Code – 2024 Edition:

The Uniform Mechanical Code contains complete requirements for the installation and maintenance of heating, ventilating, cooking and refrigeration systems.

Uniform Mechanical Code Illustrated Training Manual:
CMC § 101.2.2 Medium relevance — show source text
CFC—25: California Fire Code

101.2.2, 101.4.2, 301.3.1, 302.2, 307.1, 308.1, 802.2.1, 802.2.3, 803.2.3, 803.4.1.1, 803.4.1.2, 803.4.1.3, 803.4.1.4, 803.4.1.5, 803.4.1.6, Table 804.5.1.1(1), 904.1.5, 1011.6.1.1, 1303.1.2, 1305.2.8.1, 1305.2.14, 1305.2.14.1, 1401.2, 1501.1, 1501.5, 1502.1, 1502.1.1, 1502.2, 1502.3, 1504.1, 1507.1, 1507.2

CMC—25: California Mechanical Code

302.2, 702.7, 807.1, 902.1.1, 1008.1, 1305.2.7.1, 1305.2.8, 1305.2.8.1

CPC—25: California Plumbing Code

302.2, 408.1, 702.7, 1009.1, 1009.2, 1009.3, 1009.5, 1302.1.6, 1503.1

16-4 2025 CALIFORNIA EXISTING BUILDING CODE

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

REFERENCED STANDARDS

CRC—25: California Residential Code

101.2, 101.4.1, 104.3.1, 109.3.3, 109.3.10, 302.2, 307.1, 308.1, 401.3, 402.1, 405.2.6, 502.2, 502.3, 502.4, 503.2, 503.3, 503.11, 505.2, 505.3, 507.3, 701.3, 702.4, 702.5, 706.2, 708.1, 805.2, 806.4, 809.1, 906.2, 907.1, 1011.2.1, 1103.1, 1103.2, 1103.3, 1104.1, 1201.4, 1302.1.2, 1302.1.3, 1302.1.3, 1303.1.3, 1401.2, 1402.1, 1402.2, 1402.2.1, 1402.3, 1402.4, 1402.5, 1402.6

ICC 300—2023: ICC Standard on Bleachers, Folding and Telescopic Seating and Grandstands

301.1.1, 401.1.1, 1401.1.1

ICC A117.1—2017: Accessible and Usable Buildings and Facilities
CMC § 2308.8.1.2.4 Medium relevance — show source text
2308.8.1.2.4 Grounding and bonding. The structure or appurtenance used for supporting the cylinder shall be grounded in accordance with the California Electrical Code. The cylinder valve shall be bonded prior to the commencement of venting operations.

2308.8.1.2.5 Vent tube. A vent tube that will divert the gas flow to the atmosphere shall be installed on the cylinder prior to commencement of the venting and purging operation. The vent tube shall be constructed of pipe or tubing materials approved for use with CNG in accordance with Chapter 53.

The vent tube shall be capable of dispersing the gas not less than 10 feet (3048 mm) above grade level. The vent tube shall not be provided with a rain cap or other feature that would limit or obstruct the gas flow.

At the connection fitting of the vent tube and the CNG cylinder, a listed bidirectional detonation flame arrester shall be provided.

2308.8.1.2.6 Signage. Approved “No Smoking” signs complying with Section 310 shall be posted within 10 feet (3048 mm) of the cylinder support structure or appurtenance. Approved “Cylinder Shall Be Bonded” signs shall be posted on the cylinder support structure or appurtenance.

SECTION 2309—HYDROGEN MOTOR FUEL-DISPENSING AND GENERATION FACILITIES

2309.1 General. Hydrogen motor fuel-dispensing and generation facilities shall be in accordance with this section, Chapter 58 and NFPA 2. Where a fuel-dispensing facility includes a repair garage, the repair operation shall comply with Section 2311.

2309.2 Equipment. Equipment used for the generation, compression, storage or dispensing of hydrogen shall be designed for the specific application in accordance with Sections 2309.2.1 through 2309.2.3.

2309.2.1 Approved equipment. Cylinders, containers and tanks; pressure relief devices, including pressure valves; hydrogen vaporizers; pressure regulators; and piping used for gaseous hydrogen systems shall be designed and constructed in accordance with Chapters 53, 55 and 58.

2309.2.2 Listed or approved equipment. Hoses, hose connections, compressors, hydrogen generators, dispensers, motor-fueling connections and electrical equipment used for hydrogen shall be listed or approved for use with hydrogen.

2309.2.3 Electrical equipment. Electrical installations shall be in accordance with the California Electrical Code .

2309.3 Location on property. In addition to the requirements of Section 2303.1, dispensing equipment shall be located in accordance with Sections 2309.3.1 through Section 2309.3.2.

2309.3.1 Location of operations and equipment. Generation, compression, storage and dispensing equipment shall be located in accordance with Sections 2309.3.1.1 through 2309.3.1.5.5.

2309.3.1.1 Outdoors. Generation, compression or storage equipment shall be allowed outdoors in accordance with Chapter 58 and NFPA 2.

2309.3.1.2 Indoors. Generation, compression, storage and dispensing equipment shall be located in indoor rooms or areas constructed in accordance with the requirements of the California Building Code, the International Fuel Gas Code, the California Mechanical Code and NFPA 2.
CMC § 903.2.3 Medium relevance — show source text
AIR CONDITIONERS . . . . . . . . . . . . . . . . . . . . . . 903.2.3

GAS VENT CONNECTOR . . . . . . . . . . . . . (see Connectors,

gas vent)

580 2025 CALIFORNIA MECHANICAL CODE

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

INDEX

GAS VENT,

SURROUNDING SPACE . . . . . . . . . . . . . . . . . . . 802.5.11

GAS-FIRED

Air conditioners

and heat pumps . . . . . . . . . . . . . . . . . . . . . . . . 903.2

Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903.2.1

Clothes dryers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 908.3

Household cooking appliances . . . . . . . . . . . . . . . 919.3

Industrial air heaters . . . . . . . . . . . . . . . . . . . . . . . 914.0

Packaged terminal . . . . . . . . . . . . . . . . . . . . . . . . 903.3

Room heaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915.3

Toilets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928.0

GAS FIREPLACE, VENTED . . . . . . . . . . . . . . . . . . . . 912.0

GAS TURBINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602.2

GASEOUS HYDROGEN SYSTEMS . . . . . . . . . . . . . . 936.0

GAUGES, STEAM BOILERS . . . . . . . . . . . . . . . . . . 1003.3

GENERATORS

Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209.0

Emergency Diesel-Powered . . . . . . . . . . . . . . . . . 324.0

Engine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1602.0

Steam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917.2, 1011.0

GEOTHERMAL ENERGY SYSTEMS . . . . . . . . . Chapter 17

Ambient Temperature Loops . . . . . . Chapter 17 (Part V)

Closed-loop systems . . . . . . . . . . . . Chapter 17 (Part II)

CMC § 90.1 Medium relevance — show source text

[ASHRAE 90.1: TABLE 6.4.3.4.3]

Col1	OUTDOOR AIR INTAKE (CFM/ft2)	Col3	EXHAUST/RELIEF (CFM/ft2)	Col5
CLIMATE ZONE	NONMOTORIZED1	MOTORIZED	NONMOTORIZED3	MOTORIZED
0, 1, 2	0, 1, 2	0, 1, 2	0, 1, 2	0, 1, 2
Any height	20	4	20	4
3	3	3	3	3
Any height	20	10	20	10
4, 5B, 5C	4, 5B, 5C	4, 5B, 5C	4, 5B, 5C	4, 5B, 5C
Fewer than three stories	204	10	20	10
Three or more stories	204	10	204	10
5A, 6, 7, 8	5A, 6, 7, 8	5A, 6, 7, 8	5A, 6, 7, 8	5A, 6, 7, 8
Fewer than three stories	204	4	20	4
Three or more stories	204	4	204	4

For SI units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.00047 m [3] /s, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per minute per square foot = 5.08 [(L/s)/m [2] ], 1 inch water gauge = 0.249 kPa

Notes:

1 When tested in accordance with AMCA 500D.

2 Dampers smaller than 12 inches (305 mm) in height, width, or diameter need not be tested but shall be of the same design and construction as the smallest tested damper meeting the listed leakage rate requirement.

3 Nonmotorized dampers smaller than 24 inches (610 mm) in height, width, or diameter shall be permitted to have a leakage rate of 40 CFM/ft 2 [0.203 (m 3 /s)/m 2 ].

4 Where permitted by Section E 503.4.6.4.1, exception 2.

2025 CALIFORNIA MECHANICAL CODE 425

APPENDIX E

(2) Systems serving zones where humidity levels are required to be maintained with precision of not more than ±5 percent relative humidity to comply with applicable codes or accreditation standards or as approved by the Authority Having Jurisdiction.

[ASHRAE 90.1:6.4.3.6.2]

CMC § 5809.1 Medium relevance — show source text
5809.1 General. On-demand hydrogen mobile fueling operations that dispense gaseous hydrogen into the fuel tanks of motor vehicles shall comply with Sections 5809.1 through 5809.6.5. Mobile fueling of liquid hydrogen is prohibited.

5809.1.1 Approval required. Hydrogen mobile fueling operations shall not be conducted without first obtaining a permit and approval from the fire code official. Hydrogen mobile fueling operations shall occur only at approved locations. The fire code official is authorized to approve individual locations or geographic areas where mobile fueling is allowed.

5809.2 Hydrogen mobile fueling vehicle or trailer. An on-demand hydrogen mobile fueling vehicle or mobile fueling trailer shall be that which is utilized in on-demand fueling operations for the dispensing of gaseous hydrogen into the fuel tanks of motor vehicles.

5809.2.1 Hydrogen mobile fueling vehicle requirements. Each hydrogen mobile fueling vehicle or mobile fueling trailer shall comply with all local, state and federal requirements, as well as the following:
1. The hydrogen mobile fueling vehicle or mobile fueling trailer and its equipment shall be in compliance with the appropriate requirements of NFPA 2 and US DOTn requirements for the transportation of hydrogen gas.
2. Hydrogen mobile fueling vehicles or mobile fueling trailers shall only contain and dispense gaseous hydrogen.
3. The hydrogen mobile fueling vehicle or mobile fueling trailer and its equipment shall be maintained in good repair.
4. Fueling a hydrogen motor vehicle shall be from tanks or containers mounted on a mobile fueling trailer or from tanks or containers mounted on a mobile fueling vehicle. A mobile fueling operation shall not combine a mobile fueling vehicle with a mobile fueling trailer.
5. Mobile fueling vehicles and trailers shall be provided with at least one portable fire extinguisher with a minimum rating of 40-B:C on the mobile roadside service hydrogen-fueling vehicle with signage clearly indicating its location. 6. The roadside hydrogen service vehicle shall comply with all local, state and federal requirements. 7. Individual hydrogen fuel supply tanks installed on roadside hydrogen service vehicles shall have a maximum individual fuel capacity of 1,270 cubic feet (3 kg) of hydrogen. 8. The maximum aggregate amount of all hydrogen fuel in the supply tanks of roadside hydrogen service vehicles shall not exceed 4,233 cubic feet (10 kg) of hydrogen.
5809.3 Required documents. Documents developed to comply with Sections 5809.3.1 through 5809.3.3 shall be submitted to the fire code official prior to approval of the permit application to conduct mobile gaseous hydrogen fueling operations. Any modification to an approved plan shall be updated as necessary by the owner of the mobile fueling operation and maintained in compliance with Section 110.3.

5809.3.1 Safety and emergency response plan. Hydrogen mobile fueling operators shall have an approved written safety and emergency response plan that establishes policies and procedures for fire safety, release and control, personnel training and compliance with other applicable requirements of this code. Operators shall demonstrate readiness to respond to a hydrogen leak and carry out appropriate mitigation measures.

2025 CALIFORNIA FIRE CODE 58-7

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

FLAMMABLE GASES AND FLAMMABLE CRYOGENIC FLUIDS
CMC § 928.2 Medium relevance — show source text
928.2 Installation on Combustible

Floors . . . . . . . . . . . . . . . . . . . . . . 212

928.3 Vents . . . . . . . . . . . . . . . . . . . . . . 212

929.0 Appliances for Installation in Manufactured Housing . . . . . . . 212

2025 CALIFORNIA MECHANICAL CODE

929.1 General. . . . . . . . . . . . . . . . . . . . . 212

930.0 Small Ceramic Kilns . . . . . . . . . . . 212

930.1 General. . . . . . . . . . . . . . . . . . . . . 212

930.2 Installation . . . . . . . . . . . . . . . . . . 212

930.3 Fuel-Gas Controls . . . . . . . . . . . . 212

930.4 Electrical Equipment. . . . . . . . . . . 212

930.5 Installations Inside Buildings . . . . 213

930.6 Exterior Installations . . . . . . . . . . . 213

931.0 Outdoor Open Flame Decorative Appliances . . . . . . . . . 213

931.1 General. . . . . . . . . . . . . . . . . . . . . 213

932.0 Evaporative Cooling Systems. . . . 213

932.1 General. . . . . . . . . . . . . . . . . . . . . 213

932.2 Location . . . . . . . . . . . . . . . . . . . . 213

932.3 Access, Inspection, and Repair. . . 213

932.4 Installation . . . . . . . . . . . . . . . . . . 213

933.0 Refrigeration Appliances . . . . . . . 213

933.1 Self-Contained Refrigerators and Freezers . . . . . . . . . . . . . . . . 213

933.2 Unit Coolers . . . . . . . . . . . . . . . . . 214

933.3 Self-Contained Mechanical

Refrigeration Systems . . . . . . . . . 214

934.0 Ductless Mini-Split Systems Installation . . . . . . . . . . . . . . . . . . 214

934.1 General. . . . . . . . . . . . . . . . . . . . . 214

935.0 Air Filter Appliances . . . . . . . . . . . 214

935.1 Electrostatic Air Cleaners . . . . . . . 214

935.2 High-Efficiency Particulate Air Filter Units . . . . . . . . . . . . . . . . 214

936.0 Gaseous Hydrogen Systems . . . . 214

936.1 General. . . . . . . . . . . . . . . . . . . . . 214

937.0 Compressed Natural Gas (CNG) Vehicular Fuel Systems . . . . . . . . 214

937.1 General. . . . . . . . . . . . . . . . . . . . . 214

938.0 Dehumidifiers . . . . . . . . . . . . . . . . 214

Frequently asked questions

Do I need a special mechanical permit to install a sauna heater?

Yes. The CMC requires sauna heaters to be listed to UL 875 and installed per the manufacturer; inspectors will expect listing documentation and that installation follows the instructions. See § 939.1.

Does the CMC give installation distances and ventilation rates for hydrogen or CNG systems?

No. The CMC requires that gaseous hydrogen systems follow NFPA 2 and that CNG fueling systems follow NFPA 52; the technical details (distances, ventilation rates, equipment capacities) are contained in those referenced standards and in the California Fire Code. See § 936.1 and § 937.1.

Can I install a non‑listed CNG dispenser if it’s “low flow”?

No. The CMC requires that residential and non‑residential CNG appliances be listed to the specified ANSI/CSA standards (NGV 5.1 for residential, NGV 5.2 for non‑residential) and installed per the manufacturer and NFPA 52. Check the appliance listing before installation. See § 937.1.

If my project involves hydrogen fueling, do I only follow the CMC?

No. The CMC directs you to NFPA 2 for hydrogen systems (see § 936.1), but hydrogen dispensing/quantities/siting/permits are also regulated in the California Fire Code and related chapters — you must comply with both.

What if the manufacturer’s instructions conflict with the referenced NFPA standard?

Follow the more restrictive requirement as determined by the Authority Having Jurisdiction; the CMC requires compliance with both the referenced standard and the manufacturer’s instructions, so resolve conflicts with the AHJ and supporting listed‑product documentation. See § 937.1 and § 939.1.

Ask about the CMC

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

Start Free Trial

Related in the CMC

Infrared heaters — support, clearances and installation in commercial spaces

Incinerators and crematories — field‑constructed vs factory‑built and residential limits

Unit coolers, ductless mini‑split systems and dehumidifiers — listings and installation basics

Other Specific Appliances (Incinerators, Heaters, Refrigeration, Specialty)

California Mechanical Code