CMC · California Mechanical Code
Where may hazardous process piping be located (exit corridors, concealed spaces)?
In plain terms: Hazardous process piping is generally not allowed in exit corridors or concealed spaces unless you meet the specific, strict conditions in the California Mechanical Code — sprinklers (unless space <6 in.), ventilation (≥6 ACH), a separate receptor for liquid leaks, a 1‑hour fire‑rated enclosure with fire assemblies on openings, accessible emergency shutoffs, and Class I, Division 2 electrical equipment. These requirements are found in **§ 1406.2** and **§ 1406.2.1** (and its subsections).
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Hazardous Process Piping (HPP) generally shall not be located within exit corridors, within portions of means of egress required to be enclosed in fire‑resistive construction, or in concealed spaces in or above areas not classified as Group H occupancies, except where specifically permitted by the limited provisions in § 1406.2.1. The conditions that allow HPP inside the space defined by corridor walls and the floor/roof above are governed by sprinkler, ventilation, receptor, separation, emergency‑shutoff and electrical requirements in § 1406.2.1 and its subsections. See § 1406.2 for the identification/containment requirements that also apply to HPP located in service corridors.
The baseline rule: HPP is not allowed in exit corridors or concealed spaces unless every specific condition in § 1406.2.1 is met.
Requirements in detail
Below I summarize the decision‑relevant dimensions (where you must check values/limits) and the actions the code requires. Each item is grounded in the CMC text cited.
Key defined term (first mention)
- Hazardous Process Piping (HPP) — process piping conveying hazardous liquids or gases regulated by Chapter 14 (see § 1406.2) and identified per nationally recognized standards.
Decision table — decision‑relevant dimensions and required actions
| Decision dimension | Value / threshold | Action required | Code Reference |
|---|---|---|---|
| Allowed location in exit corridors / concealed spaces | Generally: Not allowed unless installed per § 1406.2.1 | Prohibit HPP in corridors/concealed spaces except where ALL § 1406.2.1 conditions are satisfied | § 1406.2.1 |
| Visual exposure in service corridors | N/A | HPP supply piping or tubing in service corridors shall be exposed to view and must be identified per standards | § 1406.2 |
| Sprinkler protection inside corridor space | 6 inches (152 mm) | Automatic sprinklers required within the space unless the space is less than 6 inches in the least dimension | § 1406.2.1.1 |
| Ventilation of piping space | 6 air changes per hour (ACH) | Provide ventilation ≥ 6 ACH; the space shall not be used to convey air from other areas | § 1406.2.1.2 |
| Liquid piping leakage control (receptor) | N/A | Where piping carries HPP liquids, install a receptor below to collect and drain leaks to an approved location; the 1‑hour enclosure cannot be used as the receptor | § 1406.2.1.3 |
| Separation / fire rating between piping space and corridor/occupancy | 1 hour | Enclose HPP supply piping and HPP nonmetallic waste lines from the corridor/occupancies (except certain H Group occupancies) by construction having a fire‑protection rating of not less than 1 hour; access openings must be protected by approved fire assemblies | § 1406.2.1.4 |
| Emergency shutoff valves | Readily accessible at specified locations | Install manual or automatic remotely‑activated fail‑safe shutoff valves (except on waste lines) at branch connections into fabrication areas and at entries into exit corridors; excess flow valves as required by the fire code | § 1406.2.1.5 |
| Electrical equipment in piping space | Class designation | Electrical wiring and equipment in the piping space shall be approved for Class I, Division 2 hazardous locations | § 1406.2.1.6 |
| Identification of piping | N/A | Piping must be identified per nationally recognized standards to indicate the material being transported | § 1406.2 |
Notes:
- The baseline prohibition is in § 1406.2.1; the detailed conditional allowances and requirements appear in subsections § 1406.2.1.1 through § 1406.2.1.6.
How the separation enclosure must be built
- The HPP piping space must be separated from the exit corridor/occupancy by construction having a 1‑hour fire‑protection rating; where gypsum wallboard is used, joints on the piping side need not be taped if joints occur over framing members. Access openings into the enclosure must be protected by approved fire assemblies. See § 1406.2.1.4 for the specifics.
Exceptions & special cases
- Occasional transverse crossings of a corridor by supply piping that is enclosed within the corridor need not comply with § 1406.2.1.1 through § 1406.2.1.6 (the limited exception for crossings). Use this only for occasional transverse crossings — it is not a general allowance to route HPP along corridors.
- The general prohibition in § 1406.2.1 does allow HPP inside the space defined by corridor walls and the floor/roof above, or in concealed spaces above other occupancies, but only when ALL the subsection requirements (sprinklers, ventilation, receptor for liquids, separation, shutoffs, electrical classification) are satisfied. Do not treat any single condition as adequate on its own.
- The code provides a related framework for hazardous production material (HPM) piping in the California Building Code and Fire Code; those parallel provisions contain similar conditions (sprinklers, ventilation, receptors, 1‑hour separation) for HPM in corridors and concealed spaces — if the installation also triggers Building/Fire Code sections, coordinate compliance. See the Building Code/Fire Code cross‑references in the materials returned.
Common mistakes
- Assuming any enclosure equals compliance: simply placing piping inside a boxed chase does not comply unless the enclosure meets the 1‑hour separation and the other subsection requirements (sprinklers, ventilation, receptor, shutoffs, electrical classification). § 1406.2.1.4 must be satisfied.
- Forgetting ventilation or using the chase as an air plenum: the piping space must have ≥ 6 ACH and shall not be used to convey air from other areas (§ 1406.2.1.2).
- Using the 1‑hour enclosure itself as the liquid receptor: the code explicitly forbids using the 1‑hour enclosure as part of the receptor that collects liquid HPP leaks (see § 1406.2.1.3).
- Missing required emergency shutoff valve access points (branch connections and corridor entries) — valves must be readily accessible and are mandatory except for waste lines (§ 1406.2.1.5).
- Not identifying HPP piping per nationally recognized standards as required by § 1406.2.
Worked example — concrete scenario
Scenario: A semiconductor fab has a corridor that separates production from support spaces. You need to route a liquid chemical supply line above the corridor within the space defined by the corridor walls and the roof slab above.
Steps to verify code compliance:
- Baseline: such routing is allowed only if you meet § 1406.2.1 and subsections. Confirm that is the basis for the allowance.
- Sprinklers: measure the available least dimension of the piping space. If the space above the corridor has a minimum clearance of 8 inches, automatic sprinklers are required (they are required unless the space is less than 6 inches). So you must install sprinklers per § 1406.2.1.1.
- Ventilation: design ventilation to provide ≥ 6 ACH and ensure the space is not used to convey building air — document ventilation calculations per § 1406.2.1.2.
- Receptor: because the line carries liquid HPP, provide a receptor sized to collect leakage and route it to an approved drain. Do not rely on the 1‑hour enclosure for this function (see § 1406.2.1.3).
- Separation: enclose the piping space from the corridor with construction rated not less than 1 hour; protect any access openings with approved fire assemblies. If using gypsum wallboard, you may leave joints untaped on the piping side provided joints occur over framing members — follow § 1406.2.1.4.
- Shutoff valves: provide a readily accessible manual or remotely‑activated fail‑safe shutoff valve at the branch into the fabrication area and at the entry into the corridor, as required by § 1406.2.1.5.
- Electrical classification: any electrical equipment/wiring in the piping space must be Class I, Division 2 approved per § 1406.2.1.6.
- Identification & drainage: mark the piping per nationally recognized standards and provide approved means to direct spilled materials to containment/drainage per § 1406.2.
If any of these items cannot be satisfied, you must reroute the piping outside the corridor/concealed space or provide an alternate compliant path (for example, a service chase in an H occupancy or exterior routing).
Related provisions
- § 1406.2 — Hazardous Process Piping: identification, exposure in service corridors, and liquid drainage/containment requirements.
- § 1406.2.1 — Installation in Exit Corridors and Above Other Occupancies (prohibition and conditional allowance).
- § 1406.2.1.1 — Automatic Sprinklers (6 in. threshold).
- § 1406.2.1.2 — Ventilation (≥ 6 ACH; not a conveyance for other air).
- § 1406.2.1.3 — Receptor for liquid HPP (cannot use 1‑hour enclosure as receptor).
- § 1406.2.1.4 — Separation: 1‑hour fire‑resistance rating and access protection requirements.
- § 1406.2.1.5 — Emergency Shutoff Valves (locations).
- § 1406.2.1.6 — Electrical wiring classification for piping spaces.
- Cross references: related Building Code / Fire Code provisions address similar HPM corridor/ceiling installations and should be consulted when HPM rules also apply.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 1406.0 High relevance — show source text
1406.0 Pipe, Tubing, and Fittings.
1406.1 General. Process pipe, tubing, and fittings shall comply with ASME B31.3 and shall be installed in accordance with the manufacturer’s installation instructions. Materials shall be rated for the operating temperatures and pressures of the system, and shall be compatible with the type of liquid.
1406.2 Hazardous Process Piping (HPP). HPP supply piping or tubing in service corridors shall be exposed to view. HPP piping shall be identified in accordance with nationally recognized standards to indicate the material being transported. Liquid HPP piping shall have an approved means for directing spilled materials to an approved containment or drainage system.
Liquid HPP waste or drainage systems shall be installed in accordance with the plumbing code.
1406.2.1 Installation in Exit Corridors and Above Other Occupancies. Hazardous process supply pipe shall not be located within exit corridors, within a portion of a means of egress required to be enclosed in fire-resistive construction, or in concealed spaces in or above
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PROCESS PIPING
areas not classified as Group H Occupancies, except as permitted by this subsection.
Hazardous production material piping and tubing shall be permitted to be installed within the space defined by the walls of exit corridors and the floor or roof above, or in concealed spaces above other occupancies in accordance with Section 1406.2.1.1 through Section 1406.2.1.6.
1406.2.1.1 Automatic Sprinklers. Automatic sprinklers shall be installed within the space unless the space is less than 6 inches (152 mm) in the least dimension.
1406.2.1.2 Ventilation. Ventilation at not less than
6 air changes per hour (ACH) shall be provided. The space shall not be used to convey air from other
areas.
1406.2.1.3 Receptor. Where the piping or tubing is used to transport HPP liquids, a receptor shall be installed below such piping or tubing. The receptor shall be designed to collect discharge or leakage and drain it to an approved location. The 1 hour enclosure shall not be used as part of the receptor.
1406.2.1.4 Separation. HPP supply piping and tubing and HPP nonmetallic waste lines shall be separated from the exit corridor and from an occupancy other than a semi-conductor fabrication facility classified as a Group H Occupancy by construction, as required for walls or partitions that have a fire-protection rating of not less than 1 hour. Where gypsum wallboard is used, joints on the piping side of the enclosure need not be taped, provided the joints occur over framing members. Access openings into the enclosure shall be protected by approved fire assemblies.
1406.2.1.5 Emergency Shutoff Valves. Readily accessible manual or automatic remotely activated fail-safe emergency shutoff valves shall be installed on piping and tubing other than waste lines at the following locations:
(1) At branch connections into the fabrication area.
(2) At entries into exit corridors. Excess flow valves shall be installed as required by the fire code.
CMC § 1405.2 High relevance — show source text
Excavations required for the installation of underground piping shall be kept open until such time as the piping has been inspected and approved. Where such piping is covered or concealed before such approval, it shall be exposed upon the direction of the Authority Having Jurisdiction.
1405.2 Required Inspections. The Authority Having Jurisdiction shall make the following inspections and shall either approve that portion of the work as completed or shall notify the permit holder wherein the same fails to be in accordance with this code.
1405.2.1 Rough Piping Inspection. This inspection shall be made after process piping authorized by the permit has been installed and before piping has been cov
ered or concealed. This inspection shall include a determination that the piping size, material, and installation are in accordance with the requirements of this code.
1405.2.2 Final Piping Inspection. This inspection shall be made after piping authorized by the permit has been installed and after portions thereof that are to be covered or concealed are so concealed. This inspection shall include a pressure test, at which time the piping shall stand a pressure of not less than one-and-one-half times the maximum designed operating pressure where hydraulic testing is conducted or 110 percent where testing is conducted pneumatically. Test pressures shall be held for a length of time satisfactory to the Authority Having Jurisdiction, but in no case for less than 30 minutes with no perceptible drop in pressure. HPM drain, waste, and vent piping shall be tested in accordance with the plumbing code. Tests shall be made in the presence of the Authority Having Jurisdiction. Necessary apparatus for conducting tests shall be furnished by the permit holder.
1405.3 Other Inspections. In addition to the inspections required by this section, the Authority Having Jurisdiction shall be permitted to require a special inspector, as specified in the building code, during installation of piping systems. In cases where the work authorized was installed in accordance with plans and specifications prepared by a registered design professional, the Authority Having Jurisdiction shall be permitted to require a final signed report stating that the work was installed in accordance with approved plans and specifications and the applicable provisions of this chapter.
1406.0 Pipe, Tubing, and Fittings.
1406.1 General. Process pipe, tubing, and fittings shall comply with ASME B31.3 and shall be installed in accordance with the manufacturer’s installation instructions. Materials shall be rated for the operating temperatures and pressures of the system, and shall be compatible with the type of liquid.
1406.2 Hazardous Process Piping (HPP). HPP supply piping or tubing in service corridors shall be exposed to view. HPP piping shall be identified in accordance with nationally recognized standards to indicate the material being transported. Liquid HPP piping shall have an approved means for directing spilled materials to an approved containment or drainage system.
Liquid HPP waste or drainage systems shall be installed in accordance with the plumbing code.
1406.2.1 Installation in Exit Corridors and Above Other Occupancies. Hazardous process supply pipe shall not be located within exit corridors, within a portion of a means of egress required to be enclosed in fire-resistive construction, or in concealed spaces in or above
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PROCESS PIPING
areas not classified as Group H Occupancies, except as permitted by this subsection.
CMC § 415.11.6.5 High relevance — show source text
[F] 415.11.6.5 Explosion control. Explosion control shall be provided where required by Section 414.5.1.
[F] 415.11.6.6 Exits. Where two exits are required from HPM rooms, liquid storage rooms and gas rooms, one shall be directly to the outside of the building.
[F] 415.11.6.7 Doors. Doors in a fire barrier wall, including doors to corridors, shall be self-closing fire door assemblies having a fire protection rating of not less than [3] / 4 hour.
[F] 415.11.6.8 Ventilation. Mechanical exhaust ventilation shall be provided in liquid storage rooms, HPM rooms and gas rooms at the rate of not less than 1 cubic foot per minute per square foot (0.044 L/s/m [2] ) of floor area or six air changes per hour.
Exhaust ventilation for gas rooms shall be designed to operate at a negative pressure in relation to the surrounding areas and direct the exhaust ventilation to an exhaust system.
[F] 415.11.6.9 Emergency alarm system. An approved emergency alarm system shall be provided for HPM rooms, liquid storage rooms and gas rooms.
Emergency alarm-initiating devices shall be installed outside of each interior exit door of such rooms.
Activation of an emergency alarm-initiating device shall sound a local alarm and transmit a signal to the emergency control station.
An approved emergency telephone system, local alarm manual pull stations or other approved alarm-initiating devices are allowed to be used as emergency alarm-initiating devices.
[F] 415.11.7 Piping and tubing. Hazardous production materials piping and tubing shall comply with this section and ASME B31.3.
[F] 415.11.7.1 HPM having a health-hazard ranking of 3 or 4. Systems supplying HPM liquids or gases having a health-hazard ranking of 3 or 4 shall be welded throughout, except for connections, to the systems that are within a ventilated enclosure if the material is a gas, or an approved method of drainage or containment is provided for the connections if the material is a liquid.
[F] 415.11.7.2 Location in service corridors. Hazardous production materials supply piping or tubing in service corridors shall be exposed to view.
[F] 415.11.7.3 Excess flow control. Where HPM gases or liquids are carried in pressurized piping above 15 pounds per square inch gauge (psig) (103.4 kPa), excess flow control shall be provided. Where the piping originates from within a liquid storage room, HPM room or gas room, the excess flow control shall be located within the liquid storage room, HPM room or gas room. Where the piping originates from a bulk source, the excess flow control shall be located as close to the bulk source as practical.
[F] 415.11.7.4 Installations in corridors and above other occupancies. The installation of HPM piping and tubing within the space defined by the walls of corridors and the floor or roof above, or in concealed spaces above other occupancies, shall be in accordance with Sections 415.11.7.1 through 415.11.7.3 and the following conditions:
Automatic sprinklers shall be installed within the space unless the space is less than 6 inches (152 mm) in the least dimension.
Ventilation not less than six air changes per hour shall be provided. The space shall not be used to convey air from any other area.
CMC § 5003.2.2.2 High relevance — show source text
5003.2.2.2 Additional regulations for supply piping for health-hazard materials. Supply piping and tubing for gases and liquids having a health-hazard ranking of 3 or 4 in accordance with NFPA 704 shall be in accordance with ASME B31.3 and the following:
- Piping and tubing utilized for the transmission of highly toxic, toxic or highly volatile corrosive liquids and gases shall have welded, threaded or flanged connections throughout except for connections located within a ventilated enclo
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HAZARDOUS MATERIALS—GENERAL PROVISIONS
sure if the material is a gas, or an approved method of drainage or containment is provided for connections if the material is a liquid. 2. Piping and tubing shall not be located within corridors, within any portion of a means of egress required to be enclosed in fire-resistance-rated construction or in concealed spaces in areas not classified as Group H occupancies.
Exception: Piping and tubing within the space defined by the walls of corridors and the floor or roof above or in concealed spaces above other occupancies where installed in accordance with Section 415.11.7.4 of the California Building Code for Group H-5 occupancies.
5003.2.3 Equipment, machinery and alarms. Equipment, machinery and required detection and alarm systems associated with the use, storage or handling of hazardous materials shall be listed or approved.
5003.2.4 Installation of tanks. Installation of tanks shall be in accordance with Sections 5003.2.4.1 through 5003.2.4.2.1.
5003.2.4.1 Underground tanks. Underground tanks used for the storage of liquid hazardous materials shall be provided with secondary containment. In lieu of providing secondary containment for an underground tank, an above-ground tank in an underground vault complying with Section 5704.2.8 shall be permitted.
5003.2.4.2 Above-ground tanks. Above-ground stationary tanks used for the storage of hazardous materials shall be located and protected in accordance with the requirements for outdoor storage of the particular material involved.
Exception: Above-ground tanks that are installed in vaults complying with Section 5303.16 or 5704.2.8 shall not be required to comply with location and protection requirements for outdoor storage.
5003.2.4.2.1 Marking. Above-ground stationary tanks shall be marked as required by Section 5003.5.
5003.2.5 Empty containers and tanks. Empty containers and tanks previously used for the storage of hazardous materials shall be free from residual material and vapor as defined by DOTn, the Resource Conservation and Recovery Act (RCRA) or other regulating authority or maintained as specified for the storage of hazardous material.
5003.2.6 Maintenance. In addition to the requirements of Section 5003.2.3, equipment, machinery and required detection and alarm systems associated with hazardous materials shall be maintained in an operable condition. Defective containers, cylinders and tanks shall be removed from service, repaired or disposed of in an approved manner. Defective equipment or machinery shall be removed from service and repaired or replaced. Required detection and alarm systems shall be replaced or repaired where defective.
CMC § 5003.2.2 High relevance — show source text
5003.2.2 Piping, tubing, valves and fittings. Piping, tubing, valves, and fittings conveying hazardous materials shall be designed and installed in accordance with ASME B31.1 or other approved standards, and shall be in accordance with Sections 5003.2.2.1 and 5003.2.2.2.
5003.2.2.1 Design and construction. Piping, tubing, valves, fittings and related components used for hazardous materials shall be in accordance with the following:
- Piping, tubing, valves, fittings and related components shall be designed and fabricated from materials that are compatible with the material to be contained and shall be of adequate strength and durability to withstand the pressure, structural and seismic stress and exposure to which they are subject.
- Piping and tubing shall be identified in accordance with ASME A13.1 to indicate the material conveyed.
- Manual valves or automatic remotely activated fail-safe emergency shutoff valves shall be installed on supply piping and tubing and provided with ready access at the following locations: 3.1. The point of use. 3.2. The tank, cylinder or bulk source.
- Manual emergency shutoff valves and controls for remotely activated emergency shutoff valves shall be clearly visible, provided with ready access and identified in an approved manner.
- Backflow prevention or check valves shall be provided where the backflow of hazardous materials could create a hazardous condition or cause the unauthorized discharge of hazardous materials.
Exceptions:
- Piping for inlet connections designed to prevent backflow.
- Piping for pressure relief devices.
5003.2.2.2 Additional regulations for supply piping for health-hazard materials. Supply piping and tubing for gases and liquids having a health-hazard ranking of 3 or 4 in accordance with NFPA 704 shall be in accordance with ASME B31.3 and the following:
- Piping and tubing utilized for the transmission of highly toxic, toxic or highly volatile corrosive liquids and gases shall have welded, threaded or flanged connections throughout except for connections located within a ventilated enclo
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HAZARDOUS MATERIALS—GENERAL PROVISIONS
sure if the material is a gas, or an approved method of drainage or containment is provided for connections if the material is a liquid. 2. Piping and tubing shall not be located within corridors, within any portion of a means of egress required to be enclosed in fire-resistance-rated construction or in concealed spaces in areas not classified as Group H occupancies.
Exception: Piping and tubing within the space defined by the walls of corridors and the floor or roof above or in concealed spaces above other occupancies where installed in accordance with Section 415.11.7.4 of the California Building Code for Group H-5 occupancies.
5003.2.3 Equipment, machinery and alarms. Equipment, machinery and required detection and alarm systems associated with the use, storage or handling of hazardous materials shall be listed or approved.
5003.2.4 Installation of tanks. Installation of tanks shall be in accordance with Sections 5003.2.4.1 through 5003.2.4.2.1.
CMC § 1406.2.1.5 High relevance — show source text
1406.2.1.5 Emergency Shutoff Valves. Readily accessible manual or automatic remotely activated fail-safe emergency shutoff valves shall be installed on piping and tubing other than waste lines at the following locations:
(1) At branch connections into the fabrication area.
(2) At entries into exit corridors. Excess flow valves shall be installed as required by the fire code.
1406.2.1.6 Electrical Wiring. Electrical wiring and equipment located in the piping space shall be approved for Class I, Division 2, Hazardous Locations.
Exception: Occasional transverse crossing of the corridors by supply piping that is enclosed within the corridor need not comply with Section 1406.2.1.1 through Section 1406.2.1.6.
1406.3 Special Requirements for HPP Gases. In addition to other requirements of this section, HPP gases shall comply with this subsection and the fire code.
1406.3.1 Special Provisions. Where HPP supply gas is carried in pressurized piping, a fail-safe system shall shut off flow due to a rupture in the piping. Where the piping originates from outside the building, the valve shall be located outside the building as close to the bulk source as practical.
1406.3.2 Piping and Tubing Installation. Piping and tubing shall be installed in accordance with approved standards. Supply piping for hazardous production materials having a health hazard ranking of 3 or 4 shall have welded connections throughout, unless an exhausted enclosure is provided.
Exception: Material that is incompatible with ferrous piping shall be permitted to be installed in nonmetallic piping with approved connections.
1406.3.3 Gas-Detection System. Where hazardous production material gas is used or dispensed and the physiological warning properties of the gas are at a higher level than the accepted permissible exposure limit (PEL) of the gas, a continuous gas-monitoring system shall be provided to detect the presence of the short-term hazard condition. Where dispensing occurs and flammable gases or vapors are capable of being present in quantities in excess of 25 percent of the lower explosive limit (LEL), a continuous gas-monitoring system shall be connected to the emergency control station. The maximum permitted time-weighted average exposures to be utilized shall be as published in 29 CFR 1910.1000.
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CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE
CHAPTER 15 – SOLAR ENERGY SYSTEMS
(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
Adopt Entire Chapter
Adopt Entire Chapter as
amended (amended sections
listed below)
Adopt only those sections
that are listed below
Chapter/Section
1502.CMC § 415.11.7.2 High relevance — show source text
[F] 415.11.7.2 Location in service corridors. Hazardous production materials supply piping or tubing in service corridors shall be exposed to view.
[F] 415.11.7.3 Excess flow control. Where HPM gases or liquids are carried in pressurized piping above 15 pounds per square inch gauge (psig) (103.4 kPa), excess flow control shall be provided. Where the piping originates from within a liquid storage room, HPM room or gas room, the excess flow control shall be located within the liquid storage room, HPM room or gas room. Where the piping originates from a bulk source, the excess flow control shall be located as close to the bulk source as practical.
[F] 415.11.7.4 Installations in corridors and above other occupancies. The installation of HPM piping and tubing within the space defined by the walls of corridors and the floor or roof above, or in concealed spaces above other occupancies, shall be in accordance with Sections 415.11.7.1 through 415.11.7.3 and the following conditions:
Automatic sprinklers shall be installed within the space unless the space is less than 6 inches (152 mm) in the least dimension.
Ventilation not less than six air changes per hour shall be provided. The space shall not be used to convey air from any other area.
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SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY AND USE
Where the piping or tubing is used to transport HPM liquids, a receptor shall be installed below such piping or tubing. The receptor shall be designed to collect any discharge or leakage and drain it to an approved location. The 1-hour enclosure shall not be used as part of the receptor.
HPM supply piping and tubing and nonmetallic waste lines shall be separated from the corridor and from occupancies other than Group H-5 by fire barriers or by an approved method or assembly that has a fire-resistance rating of not less than 1 hour. Access openings into the enclosure shall be protected by approved fire-protection-rated assemblies.
Ready access to manual or automatic remotely activated fail-safe emergency shutoff valves shall be installed on piping and tubing other than waste lines at the following locations:
5.1. At branch connections into the fabrication area.
5.2. At entries into corridors.
Exception: Transverse crossings of the corridors by supply piping that is enclosed within a ferrous pipe or tube for the width of the corridor need not comply with Items 1 through 5.
[F] 415.11.7.5 Identification. Piping, tubing and HPM waste lines shall be identified in accordance with ANSI A13.1 to indicate the material being transported.
[F] 415.11.8 Gas detection systems. A gas detection system complying with Section 916 shall be provided for HPM gases where the physiological warning threshold level of the gas is at a higher level than the accepted permissible exposure limit (PEL) for the gas and for flammable gases in accordance with Sections 415.11.8.1 through 415.11.8.2.
[F] 415.11.8.1 Where required. A gas detection system shall be provided in the areas identified in Sections 415.11.8.1.1 through 415.11.8.1.4.
CMC § 1406.2.1.1 High relevance — show source text
1406.2.1.1 Automatic Sprinklers. Automatic sprinklers shall be installed within the space unless the space is less than 6 inches (152 mm) in the least dimension.
1406.2.1.2 Ventilation. Ventilation at not less than
6 air changes per hour (ACH) shall be provided. The space shall not be used to convey air from other
areas.
1406.2.1.3 Receptor. Where the piping or tubing is used to transport HPP liquids, a receptor shall be installed below such piping or tubing. The receptor shall be designed to collect discharge or leakage and drain it to an approved location. The 1 hour enclosure shall not be used as part of the receptor.
1406.2.1.4 Separation. HPP supply piping and tubing and HPP nonmetallic waste lines shall be separated from the exit corridor and from an occupancy other than a semi-conductor fabrication facility classified as a Group H Occupancy by construction, as required for walls or partitions that have a fire-protection rating of not less than 1 hour. Where gypsum wallboard is used, joints on the piping side of the enclosure need not be taped, provided the joints occur over framing members. Access openings into the enclosure shall be protected by approved fire assemblies.
1406.2.1.5 Emergency Shutoff Valves. Readily accessible manual or automatic remotely activated fail-safe emergency shutoff valves shall be installed on piping and tubing other than waste lines at the following locations:
(1) At branch connections into the fabrication area.
(2) At entries into exit corridors. Excess flow valves shall be installed as required by the fire code.
1406.2.1.6 Electrical Wiring. Electrical wiring and equipment located in the piping space shall be approved for Class I, Division 2, Hazardous Locations.
Exception: Occasional transverse crossing of the corridors by supply piping that is enclosed within the corridor need not comply with Section 1406.2.1.1 through Section 1406.2.1.6.
1406.3 Special Requirements for HPP Gases. In addition to other requirements of this section, HPP gases shall comply with this subsection and the fire code.
1406.3.1 Special Provisions. Where HPP supply gas is carried in pressurized piping, a fail-safe system shall shut off flow due to a rupture in the piping. Where the piping originates from outside the building, the valve shall be located outside the building as close to the bulk source as practical.
1406.3.2 Piping and Tubing Installation. Piping and tubing shall be installed in accordance with approved standards. Supply piping for hazardous production materials having a health hazard ranking of 3 or 4 shall have welded connections throughout, unless an exhausted enclosure is provided.
Exception: Material that is incompatible with ferrous piping shall be permitted to be installed in nonmetallic piping with approved connections.
CMC § 1310.14.1 High relevance — show source text
COMPRESSOR
Flammable
gas-air mixture. . . . . . . . . . . . . . 1310.14.1, 1310.14.5
Positive displacement . . . . . . . . . . 205.0, 1111.2, 1112.2,
Refrigeration system . . . . . . . . . . . . . . . 1105.2, 1105.3,
1105.6, 1111.2, 1112.2
CONCEALED SPACES
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0
Fuel gas piping in . . . . . . . . . . . . . . . . . . . . . . . 1310.4.1
Hazardous process piping in . . . . . . . . . . . . . . 1406.2.1
Lighting units in
commercial kitchen hoods . . . . . . . . 512.2.3, 512.2.4
Used as ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.1
CONDENSATE
Cleanouts for condensate drain . . . . . . . . . . . . . 310.3.1
Control . . . . . . . . . . . . . . . . . . . . . . . . . . 310.2, 1105.10
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0
Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310.1
From air
conditioning equipment . . . . . . . . 310.1, 310.2, 310.5
From air cooling coils . . . . . . . . . . . . . . . . 310.2, 1105.7
From appliances . . . . . . . . . . . . . . . . . . . . . . . . . . 310.4
From category II and
category IV appliances . . . . . . . . . . . . . . . . . . . 802.9
From fuel gas piping . . . . . . . . . . . . . . 1310.9, 1310.9.1
From refrigeration coils . . . . . . . . . . . . . . . . . . . . . 904.7
Point of discharge . . . . . . . . . . . . . . . . . . . . . . . . . 310.5
Pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310.1.1
Waste pipe sizing . . . . . . . . . . . . . . . 310.3, Table 310.3
CONDENSER
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0
CONDENSING APPLIANCE
CMC § 912.4 High relevance — show source text
Fireplaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912.4
Fossil fuel heating equipment. . . . . . . . . . . . . E 502.6.1
Furnaces, central heating . . . . . . . . . . . . . . 904.2, 907.4
COMBUSTION AIR FROM
Bedroom or bathroom. . . . . . . . . . . . . . . . . . . . . . 902.2
Chimneys and vents . . . . . . . . . . . . . . . . . . . 802.5.11.1
Combination, indoor and outdoor. . . . . . . 701.7, F 103.0
Indoors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701.4
Louvers, grilles and screens . . . . . . . . . . . . . . . . 701.10
Mechanical supply . . . . . . . . . . . . . . . . . . . . . . . . . 701.9
Outdoors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701.6
Refrigeration machinery rooms . . . . . . . . . . . . . . 1106.5
COMMERCIAL FOOD
HEAT-PROCESSING EQUIPMENT
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0
COMPRESSOR
Flammable
gas-air mixture. . . . . . . . . . . . . . 1310.14.1, 1310.14.5
Positive displacement . . . . . . . . . . 205.0, 1111.2, 1112.2,
Refrigeration system . . . . . . . . . . . . . . . 1105.2, 1105.3,
1105.6, 1111.2, 1112.2
CONCEALED SPACES
Definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.0
Fuel gas piping in . . . . . . . . . . . . . . . . . . . . . . . 1310.4.1
Hazardous process piping in . . . . . . . . . . . . . . 1406.2.1
Lighting units in
commercial kitchen hoods . . . . . . . . 512.2.3, 512.2.4
Used as ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . 602.1
CONDENSATE
Cleanouts for condensate drain . . . . . . . . . . . . . 310.3.1
Control . . . . . . . . . . . . . . . . . . . . . . . . . . 310.2, 1105.10
CMC § 2703.7.3 High relevance — show source text
2703.7.3 Hazardous production material (HPM) rooms, gas rooms and liquid storage rooms. Electrical wiring and equipment in HPM rooms, gas rooms and liquid storage rooms shall comply with the California Electrical Code.
2703.8 Corridors and enclosures for stairways and ramps. Hazardous materials shall not be used or stored in corridors or enclosures for stairways and ramps.
2703.9 Service corridors. Hazardous materials shall not be used in an open-system use condition in service corridors.
2703.10 Automatic sprinkler system. An approved automatic sprinkler system shall be provided in accordance with Sections 2703.10.1 through 2703.10.5 and Chapter 9.
2703.10.1 Workstations and tools. The design of the sprinkler system in the area shall take into consideration the spray pattern and the effect on the equipment.
2703.10.1.1 Combustible workstations. A sprinkler head shall be installed within each branch exhaust connection or individual plenums of workstations of combustible construction. The sprinkler head in the exhaust connection or plenum shall be
27-4 2025 CALIFORNIA FIRE CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SEMICONDUCTOR FABRICATION FACILITIES
located not more than 2 feet (610 mm) from the point of the duct connection or the connection to the plenum. Where necessary to prevent corrosion, the sprinkler head and connecting piping in the duct shall be coated with approved or listed corrosion-resistant materials. Access to the sprinkler head shall be provided for periodic inspection.
Exceptions:
Approved alternative automatic fire-extinguishing systems are allowed. Activation of such systems shall deactivate the related processing equipment.
Process equipment that operates at temperatures exceeding 932°F (500°C) and is provided with automatic shutdown capabilities for hazardous materials.
Exhaust ducts 10 inches (254 mm) or less in diameter from flammable gas storage cabinets that are part of a workstation.
Ducts listed or approved for use without internal automatic sprinkler protection.
2703.10.1.2 Combustible tools. Where the horizontal surface of a combustible tool is obstructed from ceiling sprinkler discharge, automatic sprinkler protection that covers the horizontal surface of the tool shall be provided.
Exceptions:
An automatic gaseous fire-extinguishing local surface application system shall be allowed as an alternative to sprinklers. Gaseous-extinguishing systems shall be actuated by infrared (IR) or ultraviolet/infrared (UV/IR) optical detectors.
Tools constructed of materials that are listed as Class 1 or Class 2 in accordance with UL 2360 or approved for use without internal fire-extinguishing system protection.
2703.10.2 Gas cabinets and exhausted enclosures. An approved automatic sprinkler system shall be provided in gas cabinets and exhausted enclosures containing HPM compressed gases.
Exception: Gas cabinets located in an HPM room other than those cabinets containing pyrophoric gases.
2703.10.3 Pass-throughs in existing exit access corridors. Pass-throughs in existing exit access corridors shall be protected by an approved automatic sprinkler system.
2703.10.4 Exhaust ducts for HPM. An approved automatic sprinkler system shall be provided in exhaust ducts conveying gases, vapors, fumes, mists or dusts generated from HPM in accordance with this section and the California Mechanical Code .
CMC § 1401.0 High relevance — show source text
334 2025 CALIFORNIA MECHANICAL CODE
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CHAPTER 14
PROCESS PIPING
1401.0 General.
1401.1 Applicability. Except as otherwise addressed in this code, this chapter shall govern the installation of process piping in or in conjunction with a building or structure located upon the premises.
1402.0 Permit.
1402.1 General. It shall be unlawful to install, alter, or repair or cause to be installed, altered, or repaired process material piping without first obtaining a permit.
Permits for process piping shall show the total number of outlets to be provided for on each system and such other information as required by the Authority Having Jurisdiction.
Fees for process piping permits are included in Table 104.5.
1403.0 Plans Required.
1403.1 General. Plans, engineering calculations, diagrams, and other data shall be submitted in one or more sets with each application for a permit. The Authority Having Jurisdiction shall be permitted to require plans, computations, and specifications to be prepared and designed by a registered design professional.
Where plans or other data are submitted for review, a plan review fee shall be paid, as provided in Section 104.3.2.
1404.0 Workmanship.
1404.1 General. Process piping shall not be strained or bent, nor shall tanks, vessels, vats, appliances, or cabinets be supported by or develop strain or stress on the piping.
1405.0 Inspections.
1405.1 General. Upon completion of the installation, alteration, or repair of process piping, and prior to the use thereof, the Authority Having Jurisdiction shall be notified that such piping is ready for inspection.
Excavations required for the installation of underground piping shall be kept open until such time as the piping has been inspected and approved. Where such piping is covered or concealed before such approval, it shall be exposed upon the direction of the Authority Having Jurisdiction.
1405.2 Required Inspections. The Authority Having Jurisdiction shall make the following inspections and shall either approve that portion of the work as completed or shall notify the permit holder wherein the same fails to be in accordance with this code.
1405.2.1 Rough Piping Inspection. This inspection shall be made after process piping authorized by the permit has been installed and before piping has been cov
ered or concealed. This inspection shall include a determination that the piping size, material, and installation are in accordance with the requirements of this code.
1405.2.2 Final Piping Inspection. This inspection shall be made after piping authorized by the permit has been installed and after portions thereof that are to be covered or concealed are so concealed. This inspection shall include a pressure test, at which time the piping shall stand a pressure of not less than one-and-one-half times the maximum designed operating pressure where hydraulic testing is conducted or 110 percent where testing is conducted pneumatically. Test pressures shall be held for a length of time satisfactory to the Authority Having Jurisdiction, but in no case for less than 30 minutes with no perceptible drop in pressure. HPM drain, waste, and vent piping shall be tested in accordance with the plumbing code. Tests shall be made in the presence of the Authority Having Jurisdiction. Necessary apparatus for conducting tests shall be furnished by the permit holder.
Frequently asked questions
May I run HPP inside a corridor if I enclose it with a framed chase?
Only if the enclosure and the installation meet every requirement of § 1406.2.1 and its subsections (sprinklers, ventilation ≥ 6 ACH, receptor for liquids, 1‑hour separation, shutoffs, Class I, Division 2 electrical), otherwise HPP in corridors is prohibited.
What is the minimum space thickness that avoids sprinkler requirement?
If the piping space has a least dimension less than 6 inches (152 mm), you are not required to install automatic sprinklers within that space per § 1406.2.1.1.
Can the 1‑hour rated enclosure itself be used to collect liquid leaks?
No. The code explicitly states the 1‑hour enclosure shall not be used as part of the receptor; a separate receptor that drains to an approved location is required for liquid HPP. See § 1406.2.1.3.
Are occasional pipe crossings across a corridor allowed without meeting all § 1406.2.1 requirements?
Yes — occasional transverse crossings that are enclosed within the corridor are excepted from § 1406.2.1.1–.1.6, but the exception is limited to occasional transverse crossings only.
What electrical classification is required for equipment in the piping space?
Electrical wiring/equipment inside the piping space must be approved for Class I, Division 2 hazardous locations per § 1406.2.1.6.
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