CRSC · California Referenced Standards Code

What marking, enclosure, and installation requirements apply to control units?

Control units (the electronic boxes for fire/protective signaling) must have a permanent nameplate and wiring diagram, be housed in a locked, sturdy cabinet designed for the service, and have enclosures, ventilation, markings and clearances that protect people and equipment — all per CRSC **§ 12-72-102**.

Ask a question free See coverage

Last reviewed: July 6, 2026

What the code requires — plain English

A control unit used in protective signaling systems must be permanently marked, include the installation wiring diagram inside the cabinet, and be installed in a locked, substantial cabinet or metalware enclosure sized, formed and protected so electrical parts and operating mechanisms are safe from accidental contact, fouling, corrosion and physical abuse. These basic marking and enclosure rules are set out in § 12-72-102 of the CRSC.

The single most important rule: control units must be clearly identified and permanently marked, and they must be housed in a locked, robust enclosure that protects people and the equipment while permitting required access for service. § 12-72-102.

Requirements in detail

Marking (what must be on the unit)

Nameplate: a permanent nameplate with the manufacturer’s name, model number and electrical rating is required. § 12-72-102 (b)1.
Wiring diagram: a wiring diagram must be attached inside the control cabinet or metalware enclosure. § 12-72-102 (b)2.
Silencing controls: any audible-alarm silencing switch must be marked to show its normal position and must carry the permanent sign: “Do not operate the audible alarm silencing switch until the fire department has been notified.” Trouble-silencing switches must be similarly marked. § 12-72-102 (b)3.
Power terminals and installation terminals: terminal connections for the power supply and installation wiring terminals or leads must be identified/marked (power terminals as required by the California Electrical Code). § 12-72-102 (b)4–5.
Detector and circuit-specific marking: units intended for use with automatic detectors must be marked for nonrestoring detectors only unless they provide the required signal lock‑in performance (§ 12-72-103 (b), Item 14). Control units used with limited‑energy circuits must be marked to identify those circuits. § 12-72-102 (b)6–7.
Actuating‑circuit impedance: if successful operation requires a maximum impedance less than 100 ohms, that maximum impedance must be marked on the unit. § 12-72-102 (b)8.
Time-limit cutouts and mounting orientation: where a control limits alarm duration, a label must indicate the time (or that it is nonadjustable and the operating time). Equipment that must be mounted in a particular position must be so marked. § 12-72-102 (b)9–10.

Frame, enclosure and metalware (how it must be housed)

Locked, substantial cabinet or metalware enclosure: control units and combination signaling systems must be installed in locked, substantial cabinets or metalware enclosures expressly designed for the service; enclosures enclosing alarm signaling circuits must have integral key locks. § 12-72-102 (c)1.
Strength and rigidity: enclosures must resist abuse without loss of performance or creating additional fire/structural hazards. § 12-72-102 (c)2.
Protection against accidental contact: electrical parts must be located or enclosed to protect against accidental contact with uninsulated hazardous live parts. § 12-72-102 (c)3.
Protection of operating parts: gear, relays and similar mechanism must be dust‑protected (individual guards or dust‑tight cabinets). § 12-72-102 (c)4.
Material and thickness: required cast-metal and sheet-metal thicknesses are specified in Table 12-72-1A and Table 12-72-1B; listed enclosures tested for intended use may be accepted in lieu of the table values. § 12-72-102 (c)5–6.
Access and covers:
- Enclosures must have means for mounting accessible without disassembling operating parts (except removal of an assembled panel). § 12-72-102 (c)7.
- An enclosure cover must be hinged if it provides access to fuses/overload devices that normally require renewal or if opening is necessary for normal operation (hinged covers need latches/catches). Unhinged covers may be used for service‑only access if deemed suitable; unhinged covers must be secured by screws or equivalent. § 12-72-102 (c)8–9; § 12-72-102 (d)22–25.
Battery compartments:
- Primary‑battery cabinets must be key locked, moisture‑protected and constructed of approved metal — sheet iron or steel not less than No. 14 manufacturer’s standard gage. § 12-72-102 (c)10.
- Storage‑battery compartments must have total volume at least twice the battery volume, screened/vented to disperse gas, and isolated so battery gases do not affect signaling equipment. § 12-72-102 (c)11–12.
Ventilation and screening:
- Vent openings must be screened with wire not smaller than No. 16 AWG, expanded‑metal mesh or perforated metal not less than 0.042 inch (1 mm) thick; no screening opening may exceed 1/2 square inch. § 12-72-102 (c)13.
- Vent openings shall be sized/arranged so a rod of diameter 3 3/64 inch (77 mm) cannot pass (to prevent access to live parts). § 12-72-102 (c)18.

Service, maintenance, and spacing (safe access and internal clearances)

Service protection: uninsulated live parts and hazardous moving parts must be guarded or arranged to minimize accidental contact during service; components that require servicing while energized must be mounted to permit safe access without exposure to adjacent uninsulated live parts. § 12-72-102 (s)1–6.
Spacings: required through‑air and over‑surface clearances between live and dead metal parts are set in Table 12-72-1C; where listed assemblies are used the table may not apply. Spacings between same‑polarity live‑metal parts that could short and prevent operation have special minimums (e.g., not less than 1/32 inch through air and 1/16 inch over surface for 0–300 V unless otherwise allowed). Barriers of suitable insulating material may reduce spacings if mechanically sound. § 12-72-102 (t)1–4.

Decision‑relevant dimensions/values (quick reference table)

Item	Dimension / Value	When it applies	Code Reference
Maximum marked actuating‑circuit impedance	100 ohms	When unit requires max impedance < 100 Ω for operation	§ 12-72-102 (b)8
Enclosure battery metal gauge	No. 14	Primary battery metal cabinets	§ 12-72-102 (c)10
Battery compartment volume	≥ 2 × battery volume	Storage battery compartments	§ 12-72-102 (c)11
Vent screen wire size	No. 16 AWG	Screen openings for ventilation	§ 12-72-102 (c)13
Max screen opening area	1/2 square inch	Size limit for individual screening openings	§ 12-72-102 (c)13
Rod exclusion diameter	3 3/64 in (77 mm)	Vent/opening design to prevent tool insertion	§ 12-72-102 (c)18
Perforated sheet thickness	≥ 0.042 in (1 mm)	Perforated or expanded sheet metal for vents	§ 12-72-102 (c)19
Hinged cover required	Hinged + latch	When cover gives access to fuses or necessary for normal operation	§ 12-72-102 (c)8; § 12-72-102 (d)22–25

Exceptions & special cases

Enclosure material/thickness requirements in the tables may be waived for enclosures that have been listed by a nationally recognized testing laboratory for the intended purpose; the test report must note such acceptance. § 12-72-102 (c)6.
An unhinged cover is permitted for service‑only access if investigation shows it is suitable; unhinged covers must be secured with screws or equivalent requiring a tool to remove. § 12-72-102 (c)9.
A hinged cover is not required where the only enclosed fuses protect internal circuit subassemblies (subject to required marking such as “Circuit Fuse(s) Inside—Disconnect Power Prior to Servicing”). § 12-72-102 (d)24.

Common mistakes

Failing to attach the required wiring diagram inside the cabinet (marking requirement). § 12-72-102 (b)2.
Leaving control‑unit cabinets unlocked or using inadequate enclosures not designed for the service. § 12-72-102 (c)1–2.
Not marking special circuits (limited‑energy, detector compatibility, time‑limit cutouts, or maximum impedance) as required — leads to installer confusion and possible misapplication. § 12-72-102 (b)6–9.
Improper vent screening (wrong wire size or oversized openings) or poor ventilation location that allows battery gases to contaminate electronics. § 12-72-102 (c)11–13.
Using thin or unlisted sheet metal enclosures that do not meet Table requirements and lack listing evidence. § 12-72-102 (c)5–6.

Worked example — applying the rules with numbers

Scenario: A control unit requires the actuating circuit impedance be no more than 75 ohms for reliable operation, contains a sealed storage battery pack that occupies 12 L of volume, and the cabinet will have a vented battery compartment.

Marking: Because the required impedance is less than 100 ohms, the unit must have the maximum actuating‑circuit impedance (75 Ω) marked on the nameplate or unit. § 12-72-102 (b)8.
Battery compartment sizing: The storage battery compartment must have total volume ≥ 2 × 12 L = 24 L and provide screened ventilation and dispersion of gases. § 12-72-102 (c)11–12.
Screening and venting: Use wire screening of No. 16 AWG or equivalent expanded‑metal/perforated metal ≥ 0.042 in thick; ensure each opening is ≤ 1/2 sq in and arrange vents so battery gases disperse away from the control electronics. § 12-72-102 (c)13.
Access and security: Install the control unit in a locked, substantial cabinet with an integral key lock; label the cabinet with manufacturer/model/electrical rating and place the wiring diagram inside the cabinet door. § 12-72-102 (b)1–2; (c)1.

Related provisions (CRSC sections to consult)

§ 12-72-101 — Test report contents and required documentation for control units (wiring diagrams, manuals, photographs).
§ 12-72-103 — Performance tests and referenced performance requirements (e.g., detector lock‑in performance referenced by marking rules).
§ 12-72-303 — (Detector requirements and supervising circuits) — consult for detector‑related marking and electrical supervision details referenced by control‑unit marking.
Table references: Table 12-72-1A, Table 12-72-1B, Table 12-72-1C — enclosure thickness and spacing tables referenced in the enclosure and spacing subsections.

Code references

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

CRSC § 12-72 High relevance — show source text
The report of investigation shall include routing of circuits for any equipment or devices which are not necessary for the transmission of a fire alarm signal.

(b) Marking.
1. Control units and combination signaling systems shall be plainly and permanently marked with a nameplate bearing the manufacturer’s name, model number and electrical rating. Enclosures and castings shall have die stamped or cast identifying numbers or other readily identifiable markings. Component parts shall be fully described or identified by manufacturer’s name and model number.
2. A wiring diagram of the control unit or combination signaling system shall be attached inside the control cabinet or metalware enclosure.
3. An audible alarm silencing switch when provided, shall be marked to indicate its normal position unless it is of the automatically restoring type. A permanently attached metal or equivalent sign shall bear the following words, “Do not operate the audible alarm silencing switch until the fire department has been notified.” The trouble signal silencing switch, unless of the automatically restoring type, shall be marked to indicate its normal on position.
4. Terminal connections for the power supply shall be marked or identified as required by the California Electrical Code.
5. Installation wiring terminals or leads shall be marked or otherwise plainly evident.
6. A control unit designed for use with automatic detectors shall be marked for use with nonrestoring types of detectors only, unless the control unit provides signal lock-in performance required by Section 12-72-103 (b), Item 14.
7. A control unit designed for use with limited-energy circuits shall be marked to identify the particular circuits in which the energy is limited.
8. The maximum impedance of each actuating circuit shall be marked when the value for successful operation is less than 100 ohms.
9. A control unit designed to limit the duration of an alarm signal by means of a time-limit cutout shall be marked to indicate the time for which it is to be adjusted; nonadjustable time-limit cutouts shall be marked to indicate time at which it will operate. [See Sections 12-72-103 (l), Items 1 and 2.]
10. Equipment required to be mounted in a definite position in order to function properly shall be marked to indicate correct mounting position.
(c) Frame, enclosure and metalware.
1. Control units and combination signaling systems shall be installed in locked substantial cabinets or metalware enclosures and shall be of a type expressly designed for the service for which they are used. Control unit cabinets and combination signaling system metalware enclosures enclosing alarm signaling circuits shall be provided with integral key locks.
2. Control unit cabinets and combination signaling system metalware enclosures shall be so formed and assembled that they will have the strength and rigidity necessary to resist the abuses to which they are liable to be subjected, without adversely
110 2025 CALIFORNIA REFERENCED STANDARDS CODE

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

PROTECTIVE SIGNALING SYSTEMS

affecting their performance, and without increasing fire hazard due to total or partial collapse with resulting reduction of spacings, loosening or displacement of parts, or other serious defects. 3. Electrical parts of a control unit or combination signaling system shall be so located or enclosed that suitable protection against accidental contact with uninsulated hazardous live parts will be provided. 4. Operating parts, such as gear mechanisms, relays and similar devices, shall be protected against fouling by dust, insects or by other material which might impair their operation, by means of individual protection or dust-tight cabinets. 5.
CRSC § 12-72 High relevance — show source text
It shall permit its application in conformity with the regulations set forth in the California Electrical Code. 2. The scheme of electrical or electronic circuiting of a control unit or combination signaling system shall provide for the degree of electrical supervision required by the California Electrical Code, and when required, shall ensure emergency operation in the presence of a fault condition. 3. Attachment plugs, bells, circuit-breakers, cords, fuse-holders, fuses, lampholders, receptacles, transformers, switches, wires, etc., provided as a part of a control unit or combination signaling system shall be investigated and judged under the requirements established by the California Electrical Code, for such devices and also with respect to their suitability for the particular application. 4. Amplifiers used in the fire-protective signaling circuits of combination systems shall be tested in accordance with UL, Inc. Standard 813 (Second Edition 1954, amended 1966 and 1967), Sound Recording and Reproducing Equipment. The exchange or replacement of amplifiers from those originally tested with a combination system shall be tested in accordance with UL, Inc. Standard 813 and evaluated in accordance with this standard to determine their suitability for use with the combination system. 5. The report of investigation shall include schematic wiring diagrams tracing the electrical or electronic circuits in their normally supervised and operating condition. Contacts of operating devices shall be shown in the normally supervised position with operating and supervisory power supplied to the equipment. 6. The report of investigation shall include photographs of the equipment with markings identifying the component parts. Operating and maintenance manuals shall be included with each control unit or combination signaling system and shall be attached to the test report and certification. 7. The report of investigation shall include an itemized list of optional equipment that has, by test, been determined as not required to provide a fire alarm signal transmission. The report of investigation shall include routing of circuits for any equipment or devices which are not necessary for the transmission of a fire alarm signal.

(b) Marking.
1. Control units and combination signaling systems shall be plainly and permanently marked with a nameplate bearing the manufacturer’s name, model number and electrical rating. Enclosures and castings shall have die stamped or cast identifying numbers or other readily identifiable markings. Component parts shall be fully described or identified by manufacturer’s name and model number.
2. A wiring diagram of the control unit or combination signaling system shall be attached inside the control cabinet or metalware enclosure.
3. An audible alarm silencing switch when provided, shall be marked to indicate its normal position unless it is of the automatically restoring type. A permanently attached metal or equivalent sign shall bear the following words, “Do not operate the audible alarm silencing switch until the fire department has been notified.” The trouble signal silencing switch, unless of the automatically restoring type, shall be marked to indicate its normal on position.
4. Terminal connections for the power supply shall be marked or identified as required by the California Electrical Code.
5. Installation wiring terminals or leads shall be marked or otherwise plainly evident.
6. A control unit designed for use with automatic detectors shall be marked for use with nonrestoring types of detectors only, unless the control unit provides signal lock-in performance required by Section 12-72-103 (b), Item 14.
7. A control unit designed for use with limited-energy circuits shall be marked to identify the particular circuits in which the energy is limited.
8. The maximum impedance of each actuating circuit shall be marked when the value for successful operation is less than 100 ohms.
CRSC § 12-72 High relevance — show source text
(c) Frame, enclosure and metalware.
1. Control units and combination signaling systems shall be installed in locked substantial cabinets or metalware enclosures and shall be of a type expressly designed for the service for which they are used. Control unit cabinets and combination signaling system metalware enclosures enclosing alarm signaling circuits shall be provided with integral key locks.
2. Control unit cabinets and combination signaling system metalware enclosures shall be so formed and assembled that they will have the strength and rigidity necessary to resist the abuses to which they are liable to be subjected, without adversely
110 2025 CALIFORNIA REFERENCED STANDARDS CODE

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

PROTECTIVE SIGNALING SYSTEMS

affecting their performance, and without increasing fire hazard due to total or partial collapse with resulting reduction of spacings, loosening or displacement of parts, or other serious defects. 3. Electrical parts of a control unit or combination signaling system shall be so located or enclosed that suitable protection against accidental contact with uninsulated hazardous live parts will be provided. 4. Operating parts, such as gear mechanisms, relays and similar devices, shall be protected against fouling by dust, insects or by other material which might impair their operation, by means of individual protection or dust-tight cabinets. 5. The thickness of cast metal for an enclosure shall be as indicated in Table 12-72-1A; except that cast metal of lesser thickness may be used if upon investigation it is shown that it has the equivalent mechanical strength. 6. Sheet metal enclosures for a control unit or combination signaling system shall be investigated and listed by a nationally recognized testing laboratory for its intended purpose or use, or shall be not less than indicated in Table 12-72-1B. 7. An enclosure shall have suitable means for mounting, accessible without disassembling any operating part except removal of a completely assembled panel such as a relay panel. 8. An enclosure cover shall be hinged if it gives access to fuses or any other overload-protective device, the normal functioning of which requires renewal, or if it is necessary to open the cover in connection with the normal operation of the control unit or combination signaling system. 9. Enclosure covers accessible for service only may be unhinged if, upon investigation, they are found to be suitable for the purpose. Unhinged covers shall be securely held in place by screws or equivalent fastening devices requiring the use of a tool for its removal.
1. Cabinets or compartments for housing of primary batteries shall be key locked with provisions for protection against moisture or movement. Metal cabinets shall be of approved design constructed of sheet iron or steel not less than No. 14 manufacturer’s standard gage.
2. Compartments for storage batteries shall have a total volume not less than twice the volume occupied by the batteries. Ventilating openings shall be provided, and so located to permit dispersion of gas while the battery is being charged at the highest rate permitted by the means incorporated in the unit.
3. The interior of the storage battery compartment shall be protected against detrimental action by the electrolyte. The compartment shall be so located or enclosed that the equipment of the signaling system will not be adversely affected by battery gases.
4. Ventilating openings shall be screened with wire screening having wires of not less than No. 16 AWG, expanded metal mesh or perforated metal of not less than 0.042 inch (1 mm) in thickness. No opening in wire screening, metal mesh or perforated metal shall exceed [ 1] / 2 square inch (322 mm [2] ) in area.
California Referenced Standards Code High relevance — show source text
000 kcmil|4/0 − 1,000 kcmil|4/0 − 1,000 kcmil|−|−|x| |8 Terminal
(two-way
configuration)|8 Terminal
(two-way
configuration)|8 Terminal
(two-way
configuration)|8 Terminal
(two-way
configuration)|−|−|x| |16 Terminal
(two-way
configuration)|16 Terminal
(two-way
configuration)|16 Terminal
(two-way
configuration)|16 Terminal
(two-way
configuration)|16 Terminal
(two-way
configuration)|16 Terminal
(two-way
configuration)|16 Terminal
(two-way
configuration)|

1 For approved suppliers, see Document 066211. 2 If using splices, 36” x 60” enclosure can accommodate up to 14 runs (7 in and 7 out or combination) of 1,000 kcmil or smaller wires. 3 350 kcmil and larger conductor installations require a 26-inch deep non-concrete enclosure or a 12-inch extension with a concrete enclosure. 4 The maximum number of runs of 750 kcmil and 1,000 kcmil conductors will be limited to a total of 2 runs (1 in and 1 out) not including or limiting other smaller conductors in the enclosure; otherwise a 36” x 60” enclosure is needed.

Rev. #22: 03−25−22 028028 Page 3 of 14

UG-1: Enclosures Greenbook Secondary Electric Underground Enclosures

Installation of Enclosures in Special-Finish Sidewalks

Notes
1. Frequently the customer or city (or other public entity) installs special-finish sidewalks (brick, tile, terrazzo, etc.). When required with enclosures through 3’ x 5’, the enclosure and standard cover shall be installed 2-inch below the final grade, and the customer or city shall furnish and install the special-finish cover as illustrated in Figure 1 on Page 4
2. The requirements for this cover shall be as follows:
A. No single section of cover shall exceed 125 pounds.

B. Provisions for removal shall be provided.

C. The special-finish cover shall be identified by the letter “E” to indicate the location of the PG&E splice enclosure.

D. This type of enclosure shall not be installed in locations where vehicular traffic is expected.

E. Caution: PG&E cover design allows for a maximum of 1/2-inch deflection under an 8,000-pound or 12,000-pound design load, depending on the specified cover.

Timber Sidewalk Surface

Full Radius Bends

Figure 1 Installation of Enclosures in Special-Finish Sidewalks

Figure 2 Installation of Non-Concrete Enclosures in Sidewalks

028028 Page 4 of 14 Rev. #22: 03−25−22

UG-1: Enclosures Greenbook Secondary Electric Underground Enclosures

Streetlight Enclosure Assembly

Notes
1. In conduit systems, enter the bottom of the box with 90 ° sweeps.
2. Do not connect more than two streetlights per enclosure.
3. Three is the maximum number of conduits allowed.
4. For streetlight applications only (see Table 1 on Page 3).
CRSC § 12-72 High relevance — show source text
2025 CALIFORNIA REFERENCED STANDARDS CODE 107

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

108 2025 CALIFORNIA REFERENCED STANDARDS CODE

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

12-72-1 PROTECTIVE SIGNALING SYSTEMS

STANDARD TEST PROCEDURES

STANDARD 12-72-1

STATE FIRE MARSHAL

SCOPE

Sec. 12-72-100.

(a) Basic. This standard represents the minimum basic requirements for the construction and performance of the protective signaling systems to be listed under this classification. The minimum design, construction and performance standards set forth herein are those deemed as minimum necessary to establish conformance to the regulations of the State Fire Marshal as set forth in the California Electrical Code, and when applicable shall be reported on in their entirety by the approved testing laboratory.

(b) Systems. This standard covers electrically operated devices and control units designed to transmit and sound alarms, supervisory and trouble signals to be employed in ordinary indoor locations in accordance with the Standards of the National Fire Protection Association for the Installation, Maintenance and Use of Proprietary, Auxiliary and Local Protective Signaling Systems, Remote Station, Nos. 72A, 72B, 72C and 72D, and the California Electrical Code. This includes combination protective signaling systems employing nonsupervised sounding circuits; combination fire alarm-communication, -program and -clock systems (hereinafter referred to as combination signaling systems); and audible devices used for both alarm and program or communication

purposes.

(c) Control unit. A control unit covered by this standard consists of a unit assembly of electrical parts having provisions for the connection of power-supply circuits routed through the control unit equipment by a prescribed scheme of circuitry; signal initiating circuits extended to separate devices by which the operating parts of the control unit are actuated for signals, and to incorporated or separate devices by which the signals are transmitted or indicated to form a coordinated combination system for definite signaling service.

TEST REPORTS

Sec. 12-72-101.

(a) Test report contents. The report shall include engineering data, and an analysis comparing the design against Section 12-72102 (a) through (u); it shall include wiring, diagrams, operating manuals and photographs as set forth in Section 12-72-102 (a), Items 5 and 6; it shall set forth the tests performed in accordance with Sections 12-72-103 (a) through (g) and the results thereof; and shall verify the correctness of the electrical rating required by Section 12-72-107.

(b) Listed devices. Electrical wiring, material, devices, combination of devices, fittings, appliances and equipment which have been tested and listed by an approved listing agency for the intended purpose and use need not be individually retested.

The report shall include the catalog number or other readily identifiable marking, the name of the approved listing agency, the laboratory test report number and date. Such individually tested and listed component parts and devices when installed in combination with other devices in a control unit or in a circuit extended from such control unit shall be subjected to the performance standard tests to determine its suitability for use in combination with other component parts, devices, circuits or equipment.
CRSC § 12-72 High relevance — show source text
1. The wires forming a screen protecting current carrying parts shall be not smaller than No. 16 AWG and the screen openings shall be not greater than [1] / 2 square inch (322 mm [2] ) in area.
2. An enclosure cover shall be hinged, sliding, pivoted or similarly attached if (1) it provides ready access to fuses or any other overcurrent protective device the normal functioning of which requires renewal, or (2) it is necessary to open the cover in connection with the normal operation of the unit.
3. With reference to the requirement of Item 22, normal operation is considered to be operation of a switch for testing or for silencing an audible signal appliance or operation of any other component of a unit which requires such action in connection with its intended performance.
4. A hinged cover is not required where the only fuse(s) enclosed is intended to provide protection to portions of internal circuits, such as may be employed on a separate printed wiring board or circuit subassembly, to prevent excessive circuit damage resulting from a fault. The use of such a fuse(s) is acceptable if the following or equivalent marking is indicated on the cover of units employing high voltage circuits: Circuit Fuse(s) Inside—Disconnect Power Prior to Servicing.
5. A hinged cover shall be provided with a latch, screw or catch to hold it closed. An unhinged cover shall be securely held in place by screws or the equivalent.
6. Glass covering an observation opening shall be held securely in place so that it cannot be readily displaced in service and shall provide adequate mechanical protection of the enclosed parts. The thickness of a glass cover shall be not less than that indicated in Table 12-72-3C.
7. A glass panel for an opening having an area of more than 144 square inches (92 903 mm [2] ) or having any dimension greater than 12 inches (305 mm), shall be supported by a continuous groove not less than [3] / 16 inch (4.7 mm) deep along all four edges of the panel.
8. A transparent material other than glass employed as a cover over an opening in an enclosure shall have mechanical strength equivalent to that of glass, not become a fire hazard or distort, or not become less transparent at the temperature to which it may be subjected under normal or abnormal service conditions.
(d) Protection against corrosion.
1. Except as indicated herein, iron and steel parts shall be suitably protected against corrosion by enameling, galvanizing, sherardizing, plating or other equivalent means.
2. These requirements apply to all enclosures whether of sheet steel or cast iron, and to all springs and other parts upon which proper mechanical operation may depend. It does not apply to minor parts such as washers, screws, bolts and the like, if the failure of such unprotected parts would not be liable to result in a hazardous condition or adversely affect the operation of the unit. Parts made of stainless steel (properly polished or treated if necessary) do not require additional protection against corrosion. Bearing surfaces should be of such materials and design as to ensure against binding due to corrosion.
(e) Insulating materials.
1. Material for the mounting of current-carrying parts shall be porcelain, phenolic composition, cold-molded composition or material which is suitable for the particular application.
2. Vulcanized fiber may be used for insulating bushings, washers, separators and barriers, but not as the sole support for uninsulated current-carrying parts of other than low-voltage circuits.
CRSC § 12-72 High relevance — show source text
(b) Normal operation.
1. A detector shall be capable of operating for all conditions of its intended performance at all sensitivity settings when employed in conjunction with any related power supply or control unit with which it is intended to be employed and indicating devices to form the system combination covered by the installation wiring diagram and any supplementary information provided.
2. The test voltage shall be in accordance with Section 12-72-303 (a), Item 5, and the combustion products detector shall be in the normal circuit supervisory standby condition and prepared for normal signaling operation when it is connected to related devices and circuits.
3. The introduction of combustion products into the detector chamber such as produced by a smoldering cotton lamp wick, rope or equivalent, shall result in the operation of the detector in its intended manner. Section 12-72-303 (p), Item 2.
(c) Power input and output. The input or output current of each circuit of a combustion products detector shall not exceed the marked rating by more than 10 percent when the detector is operated under the conditions of normal use and with the detector connected to a source of supply in accordance with Section 12-72-303 (a), Item 5.

(d) Electrical supervision.
1. All nonreliable components such as electronic tube heaters, blower motors, capacitors, functional heating elements, etc., the failure of which may result in an open or shorted condition shall be electrically supervised. See Sections 12-72-302 (e); 12-72-303 (a), Item 3; 12-72-303 (e) and 12-72-303 (s).
2. All electrical circuits formed by conductors extending from the installation wiring connections for interconnecting to a power supply or system control units the failure of which may result in an open or ground fault shall be electrically supervised either at the detector or at the control unit to which a detector would be connected. See Section 12-72-302 (e).
3. The requirements of Sections 12-72-392 (d), Items 1 and 2, do not apply to the following: A. Trouble indicating circuits. B. The circuits of a detector employed only for releasing device service if the fault results in the same operation of the unit as that obtained by detection of combustion products.
142 2025 CALIFORNIA REFERENCED STANDARDS CODE

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

PROTECTIVE SIGNALING SYSTEMS

C. A circuit for a supplementary signal annunciator, signal sounding appliance, motor controller or similar appliance provided that a break or a ground fault in no way affects the normal operation of the unit except for omission of the supplementary feature.

(e) Electrical supervision test.
1. The electrical circuits formed by conductors extending from the installation wiring connections of a detector for interconnection to a power supply source or system control unit initiating device circuit shall be electrically supervised so that the detector trouble signal or circuit is energized under any of the following fault conditions if the fault prevents normal operation of the detector for fire alarm signals. A. Single open or single ground fault of the connecting field wiring. B. Failure of a nonreliable component. See Sections 12-72-303 (d), Item 1; 12-72-303 (a), Item 3; and 12-72-303 (s).
2. A motor included in a detector, such as a blower motor which is required to operate continuously during normal operation, shall be supervised to indicate stalling or burnout.
CRSC § 1.5. High relevance — show source text
(b) Marking.
1. A detector shall be permanently marked with the following information, except where it is indicated that the information may appear on an installation wiring diagram. A. Name or identifying symbol of the manufacturer or vendor. B. Model number or equivalent and serial number or equivalent. C. Electrical rating, in volts, amperes or watts, and frequency for each circuit. May appear on the installation wiring diagram. D. Sensitivity setting and reference to the region of sensitivity such as maximum, nominal or intermediate or minimum. If a detector is intended to be adjusted in the field, the range of sensitivity is to be indicated. The sensitivity shall be indicated as an instrument reading. A sensitivity indication other than an instrument reading may be employed if it provides an equivalent indication of the sensitivity of the detector. May appear on the installation wiring diagram. E. Correct mounting position if a unit is intended to be mounted in a definite position. This information may appear on the installation wiring diagram. F. Identification of lights, switches, meters, etc., regarding their function, unless their operation is obvious. G. Maximum rating of fuse in each fuseholder. Located adjacent to the fuseholder.
134 2025 CALIFORNIA REFERENCED STANDARDS CODE

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

PROTECTIVE SIGNALING SYSTEMS

H. Reference to an installation wiring diagram, if not attached to the detector, by drawing number and issue number of date.

I. For a detector which employs a radioactive material, the following information shall be indicated directly on the unit: type, amount, radiation symbol (optional), safe disposal and a caution notice which shall read as follows: CAUTION—Contains Radioactive Material, or its equivalent wording. J. A reference to the Technical Bulletin. May appear on the installation wiring diagram. K. Reference to a specific model number or description of the instrument to be used for checking the sensitivity of the detector. May appear on the installation wiring diagram. L. A detector intended for permanent connection only to a wiring system other than metal-clad cable or conduit shall be marked to indicate the system or systems for which it is suitable. The marking shall be so located that it will be visible when power-supply connections to the detector are made or may appear on the installation wiring diagram. M. The State Fire Marshal’s listing label if required by Article 1.5. N. A detector which is not intended to be painted in the field shall be marked on the outside “DO NOT PAINT.” 2. An installation wiring diagram shall be provided with each detector illustrating the field connections to be made. The drawing may be attached to the unit or, if separate, shall be referenced in the marking attached to the unit with the drawing number and issue number and/or date.
1. The drawing shall show a pictorial view of the installation terminals or leads to which field connections are made as they would appear when viewed during an installation and the minimum internal dimensions of a back box, if not provided with the detector, shall be specified. The terminal numbers on the detector shall agree with the numbers on the drawing. A drawing not attached to the detector unit shall be marked with the name or identifying symbol of the manufacturer’s or vendor’s drawing number, and an issue number and/or date.
2. The following marking information is required to appear on the detector or the installation wiring diagram for the applicable circuits to which field connections are made. Where an electrical rating is indicated, it may be omitted if reference is made for connection to a specific control unit or equivalent. A. Supply circuit. Voltage, current or watts, and frequency. B.
CRSC § 12-72 High relevance — show source text
(s) Service and maintenance protection.
1. An uninsulated live part and hazardous moving parts within the enclosure shall be located, guarded or enclosed so as to minimize the likelihood of accidental contact by persons performing service functions which may have to be performed with the equipment energized.
2. Manual-switching devices may be located or oriented with respect to uninsulated live parts or hazardous moving parts so that manipulation of the mechanism can be accomplished in the normal direction of access if uninsulated live parts or hazardous moving parts are not located in front (in the direction of access) of the mechanism and are not located within 6 inches (152 mm) on any side or behind the mechanism, unless guarded.
3. In determining compliance with Item 2, only uninsulated live parts in high-voltage circuits are to be considered.
4. An electrical control component which may require examination, adjustment, servicing or maintenance while energized (excluding voltage measurements except for jacks or terminals specifically intended for that purpose) shall be located and mounted with respect to other components and with respect to grounded metal parts so that it is accessible for electrical service functions without subjecting persons to the likelihood of shock hazard from adjacent uninsulated live parts or to accident hazard from adjacent hazardous moving parts.
5. Other arrangements of location of components and/or guarding are also acceptable where electrical components are accessible for service as indicated by Item 4.
6. The following are not considered to be uninsulated live parts: (1) coils of controllers, relays and solenoids, and transformer windings, if the coils and windings are provided with suitable insulating overwraps, (2) enclosed motor windings, (3) terminals and (4) splices with suitable insulation and insulated wire.
(t) Spacings.
1. A detector shall provide reliably maintained spacings between uninsulated live parts and dead metal parts and between uninsulated live parts of opposite polarity. The spacings shall be not less than those indicated in Table 12-72-3E.
2. The spacing between an uninsulated live part and a wall or cover of a metal enclosure, a fitting for conduit or metal-clad cable, and any dead-metal part shall be not less than that indicated in Table 12-72-3E.
3. The through air and over surface spacings at an individual component part are to be judged on the basis of the volt-amperes used and controlled by the individual component. However, the spacing from one component to another, and from any component to the enclosure or to other uninsulated dead metal parts excluding the component mounting surface, shall be judged on the basis of the maximum voltage and total volt-ampere rating of all components in the enclosure.
4. The spacing requirements in Table 12-72-3E do not apply to the inherent spacings inside motors, except at wiring terminals, or to the inherent spacings of a component which is provided as part of the detector. Such spacings are judged on the basis of the requirements for the component. The electrical clearance resulting from the assembly of a component into the complete device, including clearances to dead metal or enclosures, shall be those indicated in Table 12-72-3E.
5. The “to walls of enclosure” spacings are not to be applied to an individual enclosure of a component part within an outer enclosure.
CRSC § 6.4 High relevance — show source text
6.4|Yes|Yes|No|No|No|No|Yes|Yes| |Spill control and
neutralization|1207.6.2|Yesc|Yesc|Yesf|No|Yes|No|Yes|Yes| |Thermal
runaway|1207.6.5|Yesd|Yes|Yese|Yese|No|Yes|Yese|Yes| |a. Not required for lead-acid and nickel-cadmium batteries at facilities under the exclusive control of communications utilities that comply with NFPA 76 and operate at less
than 50 VAC and 60 VDC.
b. Protection shall be provided unless documentation acceptable to the fire code official is provided in accordance with Section 104.2.2 that provides justification why the
protection is not necessary based on the technology used.
c. Applicable to vented-type (i.e., flooded) nickel-cadmium and lead-acid batteries.
d. Not required for vented-type (i.e., flooded) batteries.
e. The thermal runaway protection is permitted to be part of a battery management system that has been evaluated with the battery as part of the evaluation to UL 1973.
f. Not required for batteries with jelled electrolyte.|a. Not required for lead-acid and nickel-cadmium batteries at facilities under the exclusive control of communications utilities that comply with NFPA 76 and operate at less
than 50 VAC and 60 VDC.
b. Protection shall be provided unless documentation acceptable to the fire code official is provided in accordance with Section 104.2.2 that provides justification why the
protection is not necessary based on the technology used.
c. Applicable to vented-type (i.e., flooded) nickel-cadmium and lead-acid batteries.
d. Not required for vented-type (i.e., flooded) batteries.
e. The thermal runaway protection is permitted to be part of a battery management system that has been evaluated with the battery as part of the evaluation to UL 1973.
f. Not required for batteries with jelled electrolyte.|a. Not required for lead-acid and nickel-cadmium batteries at facilities under the exclusive control of communications utilities that comply with NFPA 76 and operate at less
than 50 VAC and 60 VDC.
b. Protection shall be provided unless documentation acceptable to the fire code official is provided in accordance with Section 104.2.2 that provides justification why the
protection is not necessary based on the technology used.
c. Applicable to vented-type (i.e., flooded) nickel-cadmium and lead-acid batteries.
d. Not required for vented-type (i.e., flooded) batteries.
e. The thermal runaway protection is permitted to be part of a battery management system that has been evaluated with the battery as part of the evaluation to UL 1973.
f. Not required for batteries with jelled electrolyte.|a. Not required for lead-acid and nickel-cadmium batteries at facilities under the exclusive control of communications utilities that comply with NFPA 76 and operate at less
than 50 VAC and 60 VDC.
b. Protection shall be provided unless documentation acceptable to the fire code official is provided in accordance with Section 104.2.2 that provides justification why the
protection is not necessary based on the technology used.
c. Applicable to vented-type (i.e., flooded) nickel-cadmium and lead-acid batteries.
d. Not required for vented-type (i.e., flooded) batteries.
e.
CRSC § 1.5. High relevance — show source text
May appear on the installation wiring diagram. K. Reference to a specific model number or description of the instrument to be used for checking the sensitivity of the detector. May appear on the installation wiring diagram. L. A detector intended for permanent connection only to a wiring system other than metal-clad cable or conduit shall be marked to indicate the system or systems for which it is suitable. The marking shall be so located that it will be visible when power-supply connections to the detector are made or may appear on the installation wiring diagram. M. The State Fire Marshal’s listing label if required by Article 1.5. N. A detector which is not intended to be painted in the field shall be marked on the outside “DO NOT PAINT.” 2. An installation wiring diagram shall be provided with each detector illustrating the field connections to be made. The drawing may be attached to the unit or, if separate, shall be referenced in the marking attached to the unit with the drawing number and issue number and/or date.
1. The drawing shall show a pictorial view of the installation terminals or leads to which field connections are made as they would appear when viewed during an installation and the minimum internal dimensions of a back box, if not provided with the detector, shall be specified. The terminal numbers on the detector shall agree with the numbers on the drawing. A drawing not attached to the detector unit shall be marked with the name or identifying symbol of the manufacturer’s or vendor’s drawing number, and an issue number and/or date.
2. The following marking information is required to appear on the detector or the installation wiring diagram for the applicable circuits to which field connections are made. Where an electrical rating is indicated, it may be omitted if reference is made for connection to a specific control unit or equivalent. A. Supply circuit. Voltage, current or watts, and frequency. B. Initiating device circuit connections. For detectors intended to be connected only to the initiating device circuit of a fire alarm system control unit, at least two detectors shall be shown connected to a typical initiating device circuit. For a detector intended only for releasing device service, a typical connection shall be shown. For a detector suitable for both application, typical connections representing both types of connections shall be illustrated. C. Supplementary circuits. Voltage, current or watts, and frequency rating.
3. Technical bulletin. A technical bulletin shall be provided by the manufacturer for each installation to be used as a reference by the installer. The bulletin shall include the manufacturer’s recommendations regarding typical detector locations. The information shall include guidelines on detector location, spacings, maintenance, servicing tests, etc., under various environmental conditions and physical configurations. Some conditions for which guidelines are required are:
A. Temperature B. Humidity C. Corrosive atmospheres D. Air movement (ventilating and air-conditioning systems) E. High ceilings F. Sloped ceilings G. Girder ceiling construction H. Small and large bays I. Open joist construction J. High stock piling K. Conditions produced by manufacturing processes 6. Detailed information shall be provided regarding the use of the facilities provided on the detector to monitor the sensitivity. Typical information that shall be provided includes: A. Nominal reading under clear condition B. Nominal reading when close to alarm C. Nominal reading at alarm condition D. Guidelines on instrument use for an engineering survey, installation and maintenance 7. Information regarding locations where not to install detectors shall also be provided to minimize the possibility of false alarms.
CRSC § 2309.3.1.5.2 High relevance — show source text
2309.3.1.5.2 Fire-extinguishing systems. Fuel-dispensing areas under canopies shall be equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1. The design of the sprinkler system shall be not less than that required for Extra Hazard Group 2 occupancies. Operation of the sprinkler system shall activate the emergency functions of Sections 2309.3.1.5.3 and 2309.3.1.5.4.

2309.3.1.5.3 Emergency discharge. Operation of the automatic sprinkler system shall activate an automatic emergency discharge system, which will discharge the hydrogen gas from the equipment on the canopy top through the vent pipe system.

2309.3.1.5.4 Emergency shutdown control. Operation of the automatic sprinkler system shall activate the emergency shutdown control required by Section 2309.5.3.

2309.3.1.5.5 Signage. Approved signage having 2-inch (51 mm) block letters shall be affixed at approved locations on the exterior of the canopy structure stating: “CANOPY TOP HYDROGEN STORAGE.”

2309.3.2 Canopies. Dispensing equipment need not be separated from canopies of Type I or II construction that are constructed in a manner that prevents the accumulation of hydrogen gas and in accordance with Section 406.7 of the California Building Code .

2309.4 Dispensing into motor vehicles at hydrogen motor fuel-dispensing facilities. Hydrogen motor fuel-dispensing systems, including key, code and card lock dispensing systems, shall be limited to the filling of permanently mounted motor vehicle fuel tanks on hydrogen-powered vehicles.

In addition to the requirements in Section 2311, the owner of a hydrogen motor fuel-dispensing facility shall provide for the safe operation of the system by complying with this code and the fueling protocols in NFPA 2 and through the institution of a fire safety plan submitted in accordance with Section 404, the training of employees and operators who use and maintain the system in accordance with Section 406, and provisions for hazard communication in accordance with Section 407.

Exception: Filling of nonpermanently mounted storage containers or tanks for motor fuel-dispensing system testing purposes is permitted.

2309.4.1 Dispensing systems. Dispensing systems shall be equipped with an overpressure protection device set at not greater than 140 percent of the service pressure of the fueling nozzle it supplies.

2309.5 Safety precautions. Safety precautions at hydrogen motor fuel-dispensing and generation facilities shall be in accordance with Sections 2309.5.1 through 2309.5.3.1.

2309.5.1 Protection from vehicles. Guard posts or other approved means shall be provided to protect hydrogen storage systems and use areas subject to vehicular damage in accordance with Section 312.

2309.5.1.1 Vehicle fueling pad. The vehicle shall be fueled on noncoated concrete or other approved paving material having a resistance not exceeding 1 megohm as determined by the methodology specified in EN 1081.

2309.5.2 Emergency shutoff valves. A manual emergency shutoff valve shall be provided to shut down the flow of gas from the hydrogen supply to the piping system.

2309.5.2.1 Identification. Manual emergency shutoff valves shall be identified and the location shall be clearly visible, have access and be indicated by means of a sign.

Frequently asked questions

Does the wiring diagram have to be inside the cabinet?

Yes — the CRSC requires a wiring diagram be attached inside the control cabinet or metalware enclosure. § 12-72-102 (b)2.

What if the enclosure is a listed product?

If the enclosure is listed by a nationally recognized testing laboratory for the intended use, the table thickness/spacing requirements may not apply, but the listing and report must be noted and kept with the documentation. § 12-72-102 (c)6.

Is an alarm‑silencing switch required to have a sign?

Yes — if an audible alarm silencing switch is provided it must be marked with its normal position and bear the permanent sign: “Do not operate the audible alarm silencing switch until the fire department has been notified.” § 12-72-102 (b)3.

How small can ventilation screen openings be?

Each screening opening must not exceed 1/2 square inch in area, and the wires forming the screen must be not smaller than No. 16 AWG. § 12-72-102 (c)13.

Can the cover be unhinged to save cost?

An unhinged cover is allowed only for service‑only access if acceptable upon investigation; it must be securely fastened with screws or equivalent requiring a tool for removal. § 12-72-102 (c)9.

More in California Referenced Standards Code

Ask about the CRSC

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

Start Free Trial

Related in the CRSC

What performance and endurance tests are required for protective signaling systems?

What must be included in laboratory test reports for control units?

What is the scope and basic requirements for protective signaling systems?

Control units and standard test procedures

California Referenced Standards Code