CMC · California Mechanical Code
Auxiliary equipment: dampers, controls and restrictions
The California Mechanical Code forbids putting dampers inside exhaust ducts or exhaust duct systems unless the damper (or the assembly containing it) is specifically listed for that use. Check the manufacturer’s listing and the building official before installing dampers, actuators, or electrical devices in exhaust ducts.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
The California Mechanical Code prohibits installing dampers in exhaust ducts or exhaust duct systems: § 512.1 is clear — dampers shall not be installed in exhaust ducts or exhaust duct systems. The only allowance is when the damper is specifically listed for that use or is required as part of a listed device or system (see § 512.1.1). These are mandatory, not performance-based, restrictions for exhaust ductwork.
The single most important rule: do not put a damper in an exhaust duct unless that damper (or the device containing it) is specifically listed for installation in an exhaust duct or required as part of a listed system.
Requirements in detail
Core prohibition
- What is banned: Installation of dampers inside exhaust ducts or exhaust duct systems. § 512.1 states the prohibition.
The narrow exception
- When a damper is allowed: Only where the damper is specifically listed for such use or where it is required as part of a listed device or system. That exception is set out in § 512.1.1. If the damper is part of a listed assembly (for example, a listed fan assembly or a listed hood component that contains a damper by listing), it may be installed in the exhaust duct in accordance with its listing.
Related auxiliary restrictions (context)
- The CMC also contains adjacent restrictions on other items placed in ducts (for context and common confusion): for example, § 512.2 prohibits wiring systems in ducts and limits electrical devices in ducts to those specifically listed for that use. These are separate but commonly related requirements that affect decisions about adding dampers, actuators, or controls within duct runs.
Quick decision table
| Question a designer/inspector asks | Allowed? | Code reference |
|---|---|---|
| Can I install a damper inside an exhaust duct or exhaust duct system? | No — prohibited | § 512.1 |
| Is any exception allowed? | Yes — only if the damper is specifically listed for installation in exhaust ducts or is required as part of a listed device/system | § 512.1.1 |
| Can I put electrical wiring, motors, lights, or controls in a duct? | No unless those devices are specifically listed for installation in ducts | § 512.2 |
| If a device installed in the exhaust airstream provides filtration or control, can it be located in the duct? | Only when specifically listed for such use (see related CMC provisions) | § 512.3 |
(Only the specific prohibitions/permissions above are stated in the cited CMC sections; the table above points you to the controlling sections.)
Exceptions & special cases
- Listed components only: The only path to put a damper in an exhaust duct is if that damper (or the assembly containing it) is specifically listed for that application — e.g., the manufacturer’s listing/testing explicitly permits installation in grease-laden or other exhaust airstreams. See § 512.1.1.
- Part of a listed device/system: If a listed hood, fan, or pollution-control device contains a damper as part of its listing, its installation is allowed as required by the listing (again per § 512.1.1).
- Other equipment in the exhaust path: The code addresses other items (motors, lights, filters, pollution-control devices) with similar “listed-for-use” restrictions; verify applicable CMC sections (for example § 512.2 and § 512.3) before placing anything in the airstream.
If you need a damper for operational reasons (backdraft prevention, airflow balancing, energy code requirements), the approved approaches are:
- Use an alternate method that does not place the damper inside the exhaust duct (for example, install the approved device upstream or use a listed hood/fan assembly that includes the necessary damper), or
- Specify and install a damper that is listed for installation in the type of exhaust (only then is it permitted under § 512.1.1).
Common mistakes
- Assuming any commercially available backdraft or motorized damper can be put into an exhaust duct — the code prohibits that except for listed devices (§ 512.1, § 512.1.1). Many backdraft dampers are not tested/listed for grease-laden airstreams and therefore are not allowed.
- Forgetting to check the listing: installing a damper “because the fan maker supplied one” without verifying the damper is specifically listed for exhaust duct use. The listing (not just vendor sales literature) must allow the installation in the exhaust airstream. See § 512.1.1.
- Adding actuators, wiring, or electrical controls inside ducts without confirming they are listed for duct installation — wiring and electrical devices are limited by § 512.2. Even a listed damper may require listed actuators / wiring methods if those components are in the airstream.
Worked example — restaurant Type I hood exhaust
Scenario: A restaurant has a Type I kitchen hood serving an exhaust duct that moves 1,500 cfm of grease-laden vapors. The owner wants to install a motorized backdraft damper in the exhaust duct to stop outside air when the hood fan is off.
- Code check: § 512.1 prohibits installing dampers in exhaust ducts or exhaust duct systems. Therefore, the proposed motorized backdraft damper cannot be installed in the exhaust duct as a standard unlisted component.
- Exception path: If the owner can obtain a damper that is specifically listed for use in grease-laden kitchen exhaust ducts (or the damper is part of a listed hood/fan assembly that the listing permits to contain a damper), the damper may be installed in accordance with that listing per § 512.1.1. Verify the manufacturer’s listing and installation instructions.
- Practical alternatives: Use a listed hood or fan assembly that includes a backdraft device in its listing, locate the damper outside the exhaust airstream in a manner allowed by other codes/listings, or provide approved alternate means for preventing backdraft (consult AHJ). The code text directs you to the listing exception rather than offering other specific device-level solutions.
Related provisions
- § 512.2 — Electrical equipment: wiring systems shall not be installed in ducts; motors, lights and other electrical devices only where specifically listed for such use.
- § 512.3 — Other equipment (fume incinerators, thermal recovery units, air pollution control devices) permitted in ducts only when specifically listed for that use; access and fire-extinguishing requirements also addressed.
- Section headings in Chapter 511 and 513 (air movement, bleed-air ducts, and fire-extinguishing equipment) may apply depending on the system and installed devices; check those sections when a damper is proposed as part of an assembly. Examples: § 511.4 (bleed-air/duct construction and adjustment) and § 513.3 (requirements for fire-extinguishing protection of downstream components).
If you need guidance about whether a particular damper or assembly is “listed for such use,” consult the manufacturer’s listing report and installation instructions and verify with the Authority Having Jurisdiction.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 512.0 High relevance — show source text
512.0 Auxiliary Equipment.
512.1 Dampers. Dampers shall not be installed in exhaust ducts or exhaust duct systems. [NFPA 96:9.1.1]
512.1.1 Use. Where specifically listed for such use or where required as part of a listed device or system, dampers in exhaust ducts or exhaust duct systems shall be permitted. [NFPA 96:9.1.2] 512.2 Electrical Equipment. Wiring systems of any type shall not be installed in ducts. [NFPA 96:9.2.1]
512.2.1 Device Installation in Ducts. Motors, lights, and other electrical devices shall be permitted to be installed in ducts or hoods or to be located in the path of travel of exhaust products only where specifically listed for such use. [NFPA 96:9.2.2]
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EXHAUST SYSTEMS
512.2.2 Lighting Units. Lighting units on hoods shall not be located in concealed spaces except as permitted by Section 512.2.3 and Section 512.2.4. [NFPA 96:9.2.3.2]
512.2.3 Concealed Spaces. Lighting units shall be permitted in concealed spaces where such units are part of a listed exhaust hood. [NFPA 96:9.2.3.3]
512.2.4 Listed Lighting Units. Listed lighting units specifically listed for such use and installed in accordance with the terms of the listing shall be permitted to be installed in concealed spaces. [NFPA 96:9.2.3.4] 512.2.5 Standard. Electrical equipment shall be installed in accordance with California Electrical Code, with due regard to the effects of heat, vapor, and grease on the equipment. 512.3 Other Equipment. Fume incinerators, thermal recovery units, air pollution control devices, or other devices shall be permitted to be installed in ducts or hoods or to be located in the path of travel of exhaust products where specifically listed for such use. [NFPA 96:9.3.1]
512.3.1 Access Required. Equipment shall have space provided to all access panels or doors for the safe removal and servicing of control devices, such as filters, electrostatic precipitator cells, and odor control media beds, and for cleaning of the equipment housing. [NFPA 96:9.3.1.3] 512.3.2 Downgrading. Downgrading other parts of the exhaust system due to the installation of approved devices, whether listed or not, shall not be allowed. [NFPA 96:9.3.2] 512.3.3 Fire-Extinguishing System. Any equipment installed in the path of exhaust products that provides secondary filtration or air pollution control shall be provided with an approved automatic fire-extinguishing system, installed in accordance with the fire-extinguishing system manufacturer’s instructions. [NFPA 96:9.3.3]
512.3.3.1 Protection. The fire-extinguishing system required by Section 512.3.3 shall provide protection for the component sections of the equipment, and ductwork downstream of the equipment. [NFPA 96:9.3.3.1]
CMC § 511.4.3 Medium relevance — show source text
511.4.3 Construction and Clearance. The bleed-air
duct shall have the same construction and clearance requirements as the main exhaust duct from the connection to the exhaust duct to at least 12 inches (305 mm) on both sides of the fire damper. [NFPA 96:8.4.4] 511.4.4 Adjustment. Each bleed air duct shall have a means of adjusting (e.g., by using volume dampers) the bleed air quantity. [NFPA 96:8.4.5] 511.4.5 Adjustment Location. Means to adjust the bleed air quantity shall be installed between the fire damper and the source of bleed air. [NFPA 96:8.4.6]
511.4.6 Bleed Air Duct. A bleed air duct shall not be used for the exhaust of grease-laden vapors and shall be so labeled. [NFPA 96:8.4.7]
511.4.7 Disconnect. Unused tenant exhaust connec tions to the master exhaust duct that are not used as bleed
air connections shall be disconnected and sealed at the main duct. [NFPA 96:8.4.8] 511.5 Solid-Fuel Air Movement Requirements. Where solid-fuel cooking equipment is used, exhaust and replacement air also shall be in accordance with Section 517.0.
512.0 Auxiliary Equipment.
512.1 Dampers. Dampers shall not be installed in exhaust ducts or exhaust duct systems. [NFPA 96:9.1.1]
512.1.1 Use. Where specifically listed for such use or where required as part of a listed device or system, dampers in exhaust ducts or exhaust duct systems shall be permitted. [NFPA 96:9.1.2] 512.2 Electrical Equipment. Wiring systems of any type shall not be installed in ducts. [NFPA 96:9.2.1]
512.2.1 Device Installation in Ducts. Motors, lights, and other electrical devices shall be permitted to be installed in ducts or hoods or to be located in the path of travel of exhaust products only where specifically listed for such use. [NFPA 96:9.2.2]
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EXHAUST SYSTEMS
512.2.2 Lighting Units. Lighting units on hoods shall not be located in concealed spaces except as permitted by Section 512.2.3 and Section 512.2.4. [NFPA 96:9.2.3.2]
512.2.3 Concealed Spaces. Lighting units shall be permitted in concealed spaces where such units are part of a listed exhaust hood. [NFPA 96:9.2.3.3]
CMC § 503.4.6.4.1 Medium relevance — show source text
E 503.4.6.4.1 Shutoff Damper Controls. Outdoor air intake and exhaust systems shall be equipped with motorized dampers that will automatically shut when the systems or spaces served are not in use. Outdoor air and exhaust or relief dampers shall be capable of and configured to automatically shut off during preoccupancy building warm-up, cooldown, and setback, except when the supply of outdoor air reduces energy costs or when outdoor air shall
be supplied to comply with the code require ments.
Exceptions:
(1) Nonmotorized (gravity back draft) dampers shall be permitted for exhaust and relief in buildings less than three stories in height and for outdoor air intakes and exhaust and relief dampers in buildings of any height located in Climate Zones 0, 1, 2 and 3. Nonmotorized dampers for outdoor air intakes shall be protected from direct exposure to wind.
(2) Nonmotorized dampers shall be permitted in systems with a design outdoor air intake or exhaust capacity of 300 ft [3] /min (0.142 m [3] /s) or less.
(3) Dampers shall not be required in ventilation or exhaust systems serving unconditioned spaces.
(4) Dampers shall not be required in exhaust systems serving Type 1 kitchen exhaust hoods.
(5) Dampers are not required in systems intended to operate continuously. [ASHRAE 90.1:6.4.3.4.2]
E 503.4.6.4.2 Dampers Leakage. Where outdoor air supply, and exhaust or relief dampers are required in Section E 503.4.6.4, they shall have a maximum leakage rate in accordance with Table E 503.4.6.4.2. [ASHRAE 90.1:6.4.3.4.3]
E 503.4.6.4.3 Ventilation Fan Controls. Fans with motors more than 0.75 hp (0.56 kW) shall have automatic controls in accordance with Section E 503.4.6.3.1 that are capable of and configured to shut off fans when not required.
Exception: HVAC systems intended to operate continuously. [ASHRAE 90.1:6.4.3.4.4]
E 503.4.6.5 Parking Garage Ventilation Sys- tems. Parking garage ventilation systems shall meet all of the following:
(1) Separate ventilation systems and control systems shall be provided for each parking garage section.
(2) Control systems for each parking garage section shall automatically detect and control contaminant levels and shall be capable of and configured to reduce fan airflow to 20 percent or less of design capacity.
(3) The ventilation system for each parking garage section shall have controls and devices that
result in fan motor demand of no more than 30 percent of design wattage at 50 percent of the design airflow.
Exception: Garage ventilation systems serving a single parking garage section having a total ventilation system motor nameplate horsepower (kilowatts)
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APPENDIX E
not exceeding 5 hp (3.7 kW) at fan system design conditions and where the parking garage section has no mechanical cooling or mechanical heating.
CMC § 509.1 Medium relevance — show source text
Hoods . . . . . . . . . . . . . . . . . . . . . . 114
509.1 Grease Removal Devices. . . . . . . 114
509.2 Installation . . . . . . . . . . . . . . . . . . 114
509.3 Solid-Fuel Grease Removal
Devices. . . . . . . . . . . . . . . . . . . . . 115
510.0 Exhaust Duct Systems . . . . . . . . . 115
510.1 General. . . . . . . . . . . . . . . . . . . . . 115
510.2 Clearance . . . . . . . . . . . . . . . . . . . 115
510.3 Openings . . . . . . . . . . . . . . . . . . . 115
510.4 Listed Grease Ducts . . . . . . . . . . . 116
510.5 Other Grease Ducts . . . . . . . . . . . 116
510.6 Exterior Installations . . . . . . . . . . . 117
xxxii
510.7 Interior Installations . . . . . . . . . . . 118
510.8 Underground Installations. . . . . . . 118
510.9 Termination of Type I Hood Exhaust System . . . . . . . . . . . . . . 119
510.10 Solid-Fuel Duct Systems . . . . . . . 120
511.0 Air Movement . . . . . . . . . . . . . . . . 120
511.1 Exhaust Fans for Commercial
Cooking Operations . . . . . . . . . . . 120
511.2 Airflow. . . . . . . . . . . . . . . . . . . . . . 121
511.3 Makeup Air . . . . . . . . . . . . . . . . . . 122
511.4 Common Duct (Manifold) Systems . . . . . . . . . . . . . . . . . . . . 122
511.5 Solid-Fuel Air Movement
Requirements . . . . . . . . . . . . . . . . 122
512.0 Auxiliary Equipment . . . . . . . . . . . 122
512.1 Dampers . . . . . . . . . . . . . . . . . . . . 122
512.2 Electrical Equipment. . . . . . . . . . . 122
512.3 Other Equipment . . . . . . . . . . . . . 123
512.4 Solid-Fuel Auxiliary Equipment. . . 123
513.0 Fire-Extinguishing Equipment. . . . 123
513.1 General. . . . . . . . . . . . . . . . . . . . . 123
513.2 Types of Equipment . . . . . . . . . . . 123
513.3 Simultaneous Operation . . . . . . . . 124
513.4 Fuel and Electric Power Shutoff . . 125
513.5 Manual Actuation . . . . . . . . . . . . . 125
513.6 System Annunciation . . . . . . . . . . 125
513.7 Special Design and Application . . 125
513.8 Review and Certification. . . . . . . . 125
CMC § 511.2 Medium relevance — show source text
511.2 Airflow. . . . . . . . . . . . . . . . . . . . . . 121
511.3 Makeup Air . . . . . . . . . . . . . . . . . . 122
511.4 Common Duct (Manifold) Systems . . . . . . . . . . . . . . . . . . . . 122
511.5 Solid-Fuel Air Movement
Requirements . . . . . . . . . . . . . . . . 122
512.0 Auxiliary Equipment . . . . . . . . . . . 122
512.1 Dampers . . . . . . . . . . . . . . . . . . . . 122
512.2 Electrical Equipment. . . . . . . . . . . 122
512.3 Other Equipment . . . . . . . . . . . . . 123
512.4 Solid-Fuel Auxiliary Equipment. . . 123
513.0 Fire-Extinguishing Equipment. . . . 123
513.1 General. . . . . . . . . . . . . . . . . . . . . 123
513.2 Types of Equipment . . . . . . . . . . . 123
513.3 Simultaneous Operation . . . . . . . . 124
513.4 Fuel and Electric Power Shutoff . . 125
513.5 Manual Actuation . . . . . . . . . . . . . 125
513.6 System Annunciation . . . . . . . . . . 125
513.7 Special Design and Application . . 125
513.8 Review and Certification. . . . . . . . 125
513.9 Installation Requirements . . . . . . . 125
513.10 Portable Fire Extinguishers . . . . . 125
513.11 Maintenance . . . . . . . . . . . . . . . . . 125
513.12 Solid-Fuel Fire-Extinguishing Equipment . . . . . . . . . . . . . . . . . . 126
514.0 Procedures for the Use, Inspection, Testing, and Maintenance of Equipment. . . . . . 126
514.1 Operating Procedures . . . . . . . . . 126
514.2 Inspection, Testing and Maintenance . . . . . . . . . . . . . . . . . 126
514.3 Inspection for Grease Buildup . . . 126
Table 514.3 Schedule of Inspection for Grease Buildup. . . . . . . . . . . . . . . 126
514.4 Cleaning of Exhaust Systems. . . . 126
514.5 Cooking Equipment Maintenance . 127
515.0 Minimum Safety Requirements for Cooking Equipment . . . . . . . . . 127
515.1 Cooking Equipment . . . . . . . . . . . 127
515.2 Operating Controls . . . . . . . . . . . . 128
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TABLE OF CONTENTS
516.0 Recirculating Systems . . . . . . . . . 128
516.1 General Requirements . . . . . . . . . 128
516.2 Design Restrictions. . . . . . . . . . . . 128
CMC § 170.2 Medium relevance — show source text
3(a)6, 170.2(a)3B Automatic Closing device 140.4(n), 170.2(c)4L Controls 120.2(e), 130.1(c)8, 130.5 (d)4, 140.3(a)5, 140.3(a)6, 150.1(c)3, 170.2(a)3A Dampers 150.0(m)7
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Demand shed controls 120.2(b), 120.2(h), 120.5(a)10, 160.3(a)2, 160.3(a)2B, 160.3(d)1 Door closer 120.6(a)9 Fault detection 120.5(a)12, 120.6(i)2, 160.3(d)1L Shut off control 130.1(c)1, 130.1(c)2, 130.2(c)4, Table 141.0-F, 160.5(a)2, 160.5(b)4, Table 180.2-E Valve 140.4(k)5, 170.2(c)4I Automatically Restart 120.2(e)2, 160.3(a)2 Automatically Shutting Off 120.2(e)1, 130.1(c)1A, 130.2(c)1, 130.5(d)1, 160.3(a)2, 160.5(b)4C, 150.5(c)2A, 160.6(d)1 Automatically Turn Off 130.1(c)6D, 160.5(b)4 Automatic-Off 150.0(k)2, 160.5(a)2 Automatic-On 110.9(b)4 , 130.1(f), 160.5(b)4F AUXILIARY POOL LOAD 150.0(p) Average U-Factor 120.7(a), 120.7(b), 140.3(a), 141.0(b)1, 150.0(a)1-2, 150.0(q)2, 150.1(c), 160.1(a), 160.1(b), 160.1(c), 160.1(e), 170.2(a)2-3, 180.2(a) Azimuth 110.10(b)2, 150.1(c)14, 170.2(f)
B
Backdraft Dampers 150.0(M)7, 160.3(B)G Backflow Prevention 110.3(c)4 Backup Capabilities 110.9(b)1 Backup Tank 110.3(c)3, 110.8(d)2 Backwash Valve 150.0(p) Base Flashing 141.0(B)2B, 150.2(B)1I, 180.2(b)1A Basis of Design 120.8(a), 120.8(c) Battery Storage Capacity Factors Table 140.10-B, Table 170.2-V Battery Storage System 10-115, 140.1(A), 140.1(b), 140.10(b), 150.1(b)1, 150.
CMC § 207.1.1 Medium relevance — show source text
**
A6.207.1.1 Efficiency.
A6.207.1.2 Controls for heat pumps with supplementary electric resistance heaters.
A6.207.1.3 Thermostats.
A6.207.1.4 Gas-and oil-fired furnace standby loss controls.||
|
|| |A6.207.2 Space conditioning systems.
A6.207.2.1 Supply air temperature reset controls.
A6.207.2.2 Electric resistance heating.
A6.207.2.3 Heat rejection systems.
A6.207.2.4 Hydronic system measures.
A6.207.2.5 Air distribution system duct leakage sealing.
A6.207.2.6 Variable air volume control for single zone systems.||
|
|| |A6.207.3 Service water-heating systems and equipment.
A6.207.3.1 Certification by manufacturers.
A6.207.3.2 Efficiency.
A6.207.3.3 Installation.||
|
|| |A6.207.4 Natural gas central furnaces, cooking equipment and pool and spa heaters.
Pilot lights prohibited.||||| |A6.207.5 Controls for space-conditioning systems.
A6.207.5.1 Thermostatic controls for each zone.
A6.207.5.2 Criteria for zonal thermostatic controls.
A6.207.5.3 Heat pump controls.
A6.207.5.4 Dampers for air supply and exhaust equipment.
A6.207.5.5 Automatic demand shed controls.||
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|| |A6.207.6 Pipe insulation.||||| |SECTION A6.209 Lighting||||| |A6.209.1 Lighting control devices, ballasts and luminaires.
A6.209.1.1 All devices: Instructions and calibration.
A6.209.1.2 Indicator lights.
**A6.209.1.3 Automatic time switch control devices.CMC § 717.1.1 Medium relevance — show source text
717.1.1 Ducts and air transfer openings. Ducts transitioning horizontally between shafts shall not require a shaft enclosure provided that the duct penetration into each associated shaft is protected with dampers complying with this section.
717.1.2 Ducts that penetrate fire-resistance-rated assemblies without dampers. Ducts that penetrate fire-resistance-rated walls and are not required by this section to have fire dampers shall comply with the requirements of Sections 714.3 through 714.4.3. Ducts that penetrate horizontal assemblies not required to be contained within a shaft and not required by this section to have fire dampers shall comply with the requirements of Sections 714.5 through 714.6.2.
717.1.2.1 Ducts that penetrate nonfire-resistance-rated assemblies. The space around a duct penetrating a nonfire-resistance-rated floor assembly shall comply with Section 717.6.3.
717.2 Installation. Fire dampers, smoke dampers, combination fire/smoke dampers and ceiling radiation dampers located within air distribution and smoke control systems shall be installed in accordance with the manufacturer’s instructions, the dampers’ listing and Sections 717.2.1 through 717.2.4.
717.2.1 Smoke control system. Where the installation of a fire damper will interfere with the operation of a required smoke control system in accordance with Section 909, approved alternative protection shall be utilized. Where mechanical systems including ducts and dampers utilized for normal building ventilation serve as part of the smoke control system, the expected performance of these systems in smoke control mode shall be addressed in the rational analysis required by Section 909.4.
717.2.2 Hazardous exhaust ducts. Fire dampers for hazardous exhaust duct systems shall comply with the California Mechanical Code .
717.2.3 Static dampers. Fire dampers and ceiling radiation dampers that are listed for use in static systems shall only be installed in heating, ventilation and air-conditioning systems that are automatically shut down in the event of a fire.
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FIRE AND SMOKE PROTECTION FEATURES
717.2.4 Mechanical, electrical and plumbing controls. Mechanical, electrical and plumbing controls shall not be installed in air duct systems.
Exception: Controls where the wiring is directly associated with the air distribution system. The wiring shall comply with the requirements of Section 601 of the California Mechanical Code and be as short as practicable.
717.2.4.1 Controls not permitted to be installed through dampers. Mechanical, electrical and plumbing controls shall not be installed through fire dampers, smoke dampers, combination fire/smoke dampers or ceiling radiation dampers unless otherwise permitted by the manufacturer and the listing.
717.3 Damper testing, ratings and actuation. Damper testing, ratings and actuation shall be in accordance with Sections 717.3.1 through 717.3.3.
717.3.1 Damper testing. Dampers shall be listed and labeled in accordance with the standards in this section.
- Fire dampers shall comply with the requirements of UL 555.
- Smoke dampers shall comply with the requirements of UL 555S.
- Combination fire/smoke dampers shall comply with the requirements of both UL 555 and UL 555S.
CMC § 717.2.3 Medium relevance — show source text
717.2.3 Static dampers. Fire dampers and ceiling radiation dampers that are listed for use in static systems shall only be installed in heating, ventilation and air-conditioning systems that are automatically shut down in the event of a fire.
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717.2.4 Mechanical, electrical and plumbing controls. Mechanical, electrical and plumbing controls shall not be installed in air duct systems.
Exception: Controls where the wiring is directly associated with the air distribution system. The wiring shall comply with the requirements of Section 601 of the California Mechanical Code and be as short as practicable.
717.2.4.1 Controls not permitted to be installed through dampers. Mechanical, electrical and plumbing controls shall not be installed through fire dampers, smoke dampers, combination fire/smoke dampers or ceiling radiation dampers unless otherwise permitted by the manufacturer and the listing.
717.3 Damper testing, ratings and actuation. Damper testing, ratings and actuation shall be in accordance with Sections 717.3.1 through 717.3.3.
717.3.1 Damper testing. Dampers shall be listed and labeled in accordance with the standards in this section.
- Fire dampers shall comply with the requirements of UL 555.
- Smoke dampers shall comply with the requirements of UL 555S.
- Combination fire/smoke dampers shall comply with the requirements of both UL 555 and UL 555S.
- Ceiling radiation dampers shall comply with the requirements of UL 555C or shall be tested as part of a fire-resistancerated floor/ceiling or roof/ceiling assembly in accordance with ASTM E119 or UL 263.
- Corridor dampers shall comply with requirements of both UL 555 and UL 555S. Corridor dampers shall demonstrate acceptable closure performance when subjected to 150 feet per minute (0.76 mps) velocity across the face of the damper during the UL 555 fire exposure test.
717.3.2 Damper rating. Damper ratings shall be in accordance with Sections 717.3.2.1 through 717.3.2.4.
717.3.2.1 Fire damper ratings. Fire dampers shall have the minimum rating specified in Table 717.3.2.1.
TABLE 717.3.2.1—FIRE DAMPER RATING Col2 TYPE OF PENETRATION MINIMUM DAMPER RATING (hours) Less than 3-hour fire-resistance-rated assemblies 1.5 3-hour or greater fire-resistance-rated assemblies 3 717.3.2.2 Smoke damper ratings. Smoke damper leakage ratings shall be Class I or II. Elevated temperature ratings shall be not less than 250°F (121°C).
717.3.2.3 Combination fire/smoke damper ratings. Combination fire/smoke dampers shall have the minimum rating specified for fire dampers in Table 717.3.2.1 and shall have the minimum rating specified for smoke dampers in Section 717.3.2.2.
CMC § 120.2 Medium relevance — show source text
Exception to Section 120.2(e)1: Mechanical systems serving retail stores and associated malls, restaurants, grocery stores, churches and theaters equipped with 7-day programmable timers. 2. The control shall automatically restart and temporarily operate the system as required to maintain: A. A setback heating thermostat setpoint if the system provides mechanical heating; and Exception to Section 120.2(e)2A: Thermostat setback controls are not required in nonresidential buildings in areas where the Winter Median of Extremes outdoor air temperature determined in accordance with Section 140.4(b)3 is greater than 32°F. B. A setup cooling thermostat setpoint if the system provides mechanical cooling. Exception to Section 120.2(e)2B: Thermostat setup controls are not required in nonresidential buildings in areas where the Summer Design Dry Bulb 0.5 percent temperature determined in accordance with Section 140.4(b)3 is less than 100°F.
- Occupant sensing zone controls. Where the system providing space conditioning also provides the ventilation required by Section 120.1 and includes occupant sensor ventilation control as specified in Section 120.1(d)5, the occupant sensing zone controls shall additionally comply with the following: A. In 5 minutes or less after entering occupied-standby mode as described in Section 120.1(d). i. Automatically set up the operating cooling temperature set point by 2°F or more and set back the operating heating temperature set point by 2°F or more; or ii. For multiple zone systems with Direct Digital Controls (DDC) to the zone level, setup the operating cooling temperature setpoint by 0.5°F or more and setback the operating heating temperature setpoint by 0.5°F or
more.
B. In 5 minutes or less after entering occupied-standby mode, mechanical ventilation to the zone shall remain off whenever the space temperature is between the active heating and cooling setpoints. Exception 1 to Sections 120.2(e)1, 2, 3: Where it can be demonstrated to the satisfaction of the enforcing agency that the system serves an area that must operate continuously. Exception 2 to Sections 120.2(e)1, 2, 3: Systems with full load demands of 2 kW or less, if they have a readily accessible manual shut-off switch.
Exception 3 to Sections 120.2(e) 1 and 2: Systems serving hotel/motel guest rooms, if they have a readily accessible manual shut-off switch.
2025 CALIFORNIA ENERGY CODE 73
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
NONRESIDENTIAL, HOTEL/MOTEL OCCUPANCIES, AND COVERED PROCESSES—MANDATORY REQUIREMENTS
- Hotel and motel guest rooms shall have captive card key controls, occupancy sensing controls or automatic controls such that, no longer than 30 minutes after the guest room has been vacated, setpoints are set up at least +5°F (+3°C) in cooling mode and set down at least -5°F (-3°C) in heating mode.
Exception to Section 120.2(e): Systems serving healthcare facilities.
(f) Dampers for air supply and exhaust equipment. Outdoor air supply and exhaust equipment shall be installed with dampers that automatically close upon fan shutdown.
Exception 1 to Section 120.2(f): Equipment that serves an area that must operate continuously.
Exception 2 to Section 120.2(f): Gravity and other nonelectrical equipment that has readily accessible manual damper controls.
CMC § 207.3.3 Medium relevance — show source text
**
A6.207.3.3 Installation.||
|
|| |A6.207.4 Natural gas central furnaces, cooking equipment and pool and spa heaters.
Pilot lights prohibited.||||| |A6.207.5 Controls for space-conditioning systems.
A6.207.5.1 Thermostatic controls for each zone.
A6.207.5.2 Criteria for zonal thermostatic controls.
A6.207.5.3 Heat pump controls.
A6.207.5.4 Dampers for air supply and exhaust equipment.
A6.207.5.5 Automatic demand shed controls.||
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|| |A6.207.6 Pipe insulation.||||| |SECTION A6.209 Lighting||||| |A6.209.1 Lighting control devices, ballasts and luminaires.
A6.209.1.1 All devices: Instructions and calibration.
A6.209.1.2 Indicator lights.
A6.209.1.3 Automatic time switch control devices.
A6.209.1.4 Occupant sensors, motion sensors and vacancy sensors.
A6.209.1.5 Multilevel occupant sensor.
A6.209.1.6 Automatic daylighting control devices.
A6.209.1.7 Interior Photosensors.
A6.209.1.8 Multilevel astronomical time-switch controls.
A6.209.1.9 Outdoor astronomical time-switch controls.
A6.209.1.10 Dimmers.||
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|| |A6.209.2 Indoor lighting controls.
A6.209.2.1 Area controls.
A6.209.2.2 Multilevel lighting controls.
A6.209.2.3 Daylight areas.
A6.209.2.3.1 Daylight area.
A6.209.2.3.1.2 Daylight area, primary sidelit.
**A6.209.2.3.1.3 Daylight area, secondary sidelit.CMC § 6.1507 Medium relevance — show source text
LIFT = Entering Condenser Water Temperature (°F) – Leaving Chilled Water Temperature (°F)
2. Condenser DT = Leaving Condenser Water Temperature (°F) – Entering Condenser Water Temperature (°F)
Kadj = 6.1507 – 0.30244(×) + 0.0062692(×)2 – 0.000045595(×)3
where× = Condenser DT + LIFT
COPadj = Kadj * COPstd|1. LIFT = Entering Condenser Water Temperature (°F) – Leaving Chilled Water Temperature (°F)
2. Condenser DT = Leaving Condenser Water Temperature (°F) – Entering Condenser Water Temperature (°F)
Kadj = 6.1507 – 0.30244(×) + 0.0062692(×)2 – 0.000045595(×)3
where× = Condenser DT + LIFT
COPadj = Kadj * COPstd|1. LIFT = Entering Condenser Water Temperature (°F) – Leaving Chilled Water Temperature (°F)
2. Condenser DT = Leaving Condenser Water Temperature (°F) – Entering Condenser Water Temperature (°F)
Kadj = 6.1507 – 0.30244(×) + 0.0062692(×)2 – 0.000045595(×)3
where× = Condenser DT + LIFT
COPadj = Kadj * COPstd|1. LIFT = Entering Condenser Water Temperature (°F) – Leaving Chilled Water Temperature (°F)
2. Condenser DT = Leaving Condenser Water Temperature (°F) – Entering Condenser Water Temperature (°F)
Kadj = 6.1507 – 0.30244(×) + 0.0062692(×)2 – 0.000045595(×)3
where× = Condenser DT + LIFT
COPadj = Kadj * COPstd|1. LIFT = Entering Condenser Water Temperature (°F) – Leaving Chilled Water Temperature (°F)
2. Condenser DT = Leaving Condenser Water Temperature (°F) – Entering Condenser Water Temperature (°F)
Kadj = 6.1507 – 0.30244(×) + 0.0062692(×)2 – 0.000045595(×)3
where× = Condenser DT + LIFT
COPadj = Kadj * COPstd|1. LIFT = Entering Condenser Water Temperature (°F) – Leaving Chilled Water Temperature (°F)
2. Condenser DT = Leaving Condenser Water Temperature (°F) – Entering Condenser Water Temperature (°F)
Kadj = 6.1507 – 0.30244(×) + 0.0062692(×)2 – 0.000045595(×)3
where× = Condenser DT + LIFT
COPadj = Kadj * COPstd|A6.207.1.2 Controls for heat pumps with supplementary electric resistance heaters. Heat pumps with supplementary electric resistance heaters shall have controls:
A6.207.1.2.1 That prevent supplementary heater operation when the heating load can be met by the heat pump alone; and
Frequently asked questions
Can I use a standard motorized backdraft damper in my kitchen exhaust duct?
No. § 512.1 prohibits dampers in exhaust ducts unless the damper or the assembly is specifically listed for that use; a standard motorized backdraft damper is typically not acceptable unless listed for grease-laden exhaust.
What does “listed for such use” mean here?
It means the damper or device has been tested/listed by an approved certification organization and the listing explicitly permits installation in the type of exhaust duct or exhaust airstream in question (see § 512.1.1). Check the listing and installation instructions.
If a damper is part of a listed hood/fan, is it permitted?
Yes — a damper that is required as part of a listed device or system may be installed in the exhaust duct per § 512.1.1. Install and use it according to the manufacturer’s listing and instructions.
Are electrical actuators and wiring allowed inside ducts to operate a listed damper?
Only if those electrical devices and their wiring are specifically listed for installation in ducts; otherwise wiring systems shall not be installed in ducts as noted in § 512.2. Confirm listing for the actuator/wiring as well.
Who verifies whether a damper or device is listed and acceptable?
The Authority Having Jurisdiction (AHJ) — typically the building official or the inspecting agency — verifies listing documentation and whether the proposed installation meets § 512.1 and § 512.1.1. Manufacturer listings and installation instructions should be provided to the AHJ.
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