CMC · California Mechanical Code
Open-top broiler units — domestic vs commercial requirements and hood protection
For homeowners: residential (domestic) open‑top broilers must be listed appliances and have a metal hood (≥0.0122 in thick), with a 1/4‑inch gap to the underside of cabinets and at least 24 inches from the cooking surface to combustible material; commercial broilers require Type I hood ventilation sized per Chapter 5, Part II.
Last reviewed: July 6, 2026
What the code requires — plain English
- Open-top broiler units must be listed to the referenced ANSI/CSA standards and installed per manufacturer instructions — see § 921.1.
- Domestic open-top broilers require a metal ventilating hood of specified thickness, specific clearances to combustible cabinets and the cooking top, and the hood must be at least as wide and centered over the unit — see § 921.2.
- Commercial open-top broilers must receive ventilation sized and installed in accordance with Chapter 5, Part II (Type I/Type II hood and exhaust rules) — see § 921.3 and Chapter 5 references (e.g., § 508.0, airflow tables).
The single most important rule: Domestic open-top broilers must have a metal ventilating hood and minimum clearances as specified in § 921.2; commercial broilers must be ventilated per Chapter 5, Part II (Type I hood requirements) under § 921.3.
Requirements in detail
Scope / listing
- Listed appliance: An open-top broiler unit must be listed to ANSI Z83.11/CSA 1.8 or ANSI/CSA Z21.1/CSA 1.1 and installed in accordance with the manufacturer’s instructions — § 921.1.
Domestic units (what a homeowner or residential installer needs to provide)
Key items required by § 921.2 (paraphrased from the CMC):
- Provide a metal ventilating hood of at least 0.0122 in (0.3099 mm) thickness.
- Maintain a clearance of not less than 1/4 in (6.4 mm) between the hood and the underside of any combustible material or metal cabinets.
- Maintain vertical clearance of at least 24 in (610 mm) between the cooking top and combustible material or metal cabinet, unless otherwise protected as allowed elsewhere.
- Hood must be at least as wide as the open-top broiler unit and centered over it.
- Exception: A domestic unit with an integral, listed exhaust system specifically listed for use without a hood need not have a hood if installed per Section 919.4.2(1) (manufacturer/listing instructions).
Commercial units (what a commercial kitchen requires)
§ 921.3 simply directs that commercial open-top broiler units be provided with ventilation in accordance with Chapter 5, Part II (Type I hood rules, airflow capacity, grease removal, duct construction, makeup air, etc.). Designers must follow those Chapter 5 provisions (for example, § 508.0 — Type I hoods and the hood sizing/airflow tables).
Chapter 5 examples relevant to broilers (non‑exhaustive): minimum net airflow rates for heavy‑duty or extra‑heavy‑duty hoods are set in the tables in § 508.5.1.2–508.5.1.5 (e.g., 400–700 cfm per linear foot depending on hood type and duty level) and Type I hood construction/grease‑filter requirements are in § 508.0 and § 509.0.
Decision-relevant dimensions and values (quick reference)
| Decision dimension | Value / threshold | When it applies | Code Reference |
|---|---|---|---|
| Appliance listing | ANSI Z83.11/CSA 1.8 or ANSI/CSA Z21.1/CSA 1.1 | All open-top broilers | § 921.1 |
| Hood material thickness (domestic) | Not less than 0.0122 in (0.3099 mm) | Domestic hood construction | § 921.2 |
| Clearance between hood and underside | Not less than 1/4 in (6.4 mm) | Between hood and underside of combustible material/metal cabinet | § 921.2 |
| Vertical clearance from cooking top to combustible material | At least 24 in (610 mm) | Domestic installations (unless other protections/listed exceptions apply) | § 921.2 |
| Hood sizing (width) | Hood ≥ width of the broiler and centered | Domestic | § 921.2 |
| Commercial ventilation standard | Follow Chapter 5, Part II (Type I/II hood rules) | Commercial units | § 921.3 and § 508.0 |
| Commercial hood airflow (examples) | 400–700 cfm per ft (varies by hood type & duty) | Sizing per Chapter 5 tables for heavy/extra‑heavy duty | § 508.5.1.x tables |
Hood protection / grease control (commercial)
- Commercial broilers typically require a Type I hood (captures grease/smoke) and listed grease removal devices (filters) per § 508.0 and § 509.1. Mesh filters have limitations unless listed as part of a hood. Vertical distances between grease device and cooking surface and protection for high‑temperature outlets are in § 509.2 et seq.
Exceptions & special cases
- Listed domestic open-top broilers that include an integral exhaust and are listed for use without a hood are not required to have a hood if installed per Section 919.4.2(1) and the appliance listing — see § 921.2. Confirm the appliance listing and installation instructions before omitting a hood.
- Commercial installations may qualify for listed hood assemblies or listed recirculating/ultraviolet/ventilated ceiling systems that are installed per their listings; these are exceptions to some Chapter 5 requirements but are governed by their listings and manufacturer instructions (see § 508.2 and related exceptions).
- Where grease‑removal devices are closer than standard distances to a heat source, protection (e.g., baffle plates) and minimum separation distances are required per § 509.2.2.
If a particular protective method (e.g., millboard + sheet metal, ventilated air gap systems) is proposed to reduce required clearances, refer to the applicable clearance‑reduction tables and provisions elsewhere in the CMC (e.g., Chapter 5 and Chapter 5 cross‑references) — those are situation‑specific and must be verified against the listed method.
Common mistakes
- Assuming a residential hood built like a kitchen range hood meets the metallic thickness and clearance requirements in § 921.2 — you must meet the 0.0122 in thickness and 1/4 in hood‑to‑cabinet clearance.
- Treating a commercial installation as “residential” and skipping Type I hood sizing (airflow and grease interception) per Chapter 5 — commercial open‑top broilers explicitly require Chapter 5 ventilation. Do not omit Type I hood design for commercial broilers.
- Using mesh filters or non‑listed grease removal devices without confirming listing; mesh filters are restricted unless listed as part of a hood or used with a primary listed filter — see § 509.1.1.
- Placing the grease filter or grease device too close to the cooking surface (less than 18 in (457 mm)) or not protecting it from flame/heat impingement when required — see § 509.2 and § 509.2.2.
Worked example — residential kitchen install
Scenario: Homeowner installs a listed open‑top broiler (30 in wide) in a single‑family kitchen.
Steps (apply the CMC requirements numerically):
- Confirm the appliance is listed to ANSI Z83.11/CSA 1.8 or ANSI/CSA Z21.1/CSA 1.1 and follow the manufacturer’s instructions — § 921.1.
- Provide a metal hood of thickness ≥ 0.0122 in (0.3099 mm). If using sheet metal, verify gauge meets or exceeds this thickness — § 921.2.
- Position hood so there is ≥ 1/4 in (6.4 mm) clearance between the hood and the underside of any combustible cabinet above the hood. Check with a feeler gauge or spacer during installation. § 921.2.
- Maintain vertical clearance: ensure there is ≥ 24 in (610 mm) from the cooking top (the broiler surface) to the combustible cabinet or material above. If you cannot achieve 24 in, consult the appliance listing/manufacturer or provide listed protective measures as allowed elsewhere. § 921.2.
- Make the hood at least 30 in wide (equal to the broiler width) and center it directly over the unit per § 921.2.
If the broiler is a listed model that includes an integral exhaust listed to be used without a hood and the manufacturer’s instructions permit hoodless installation, follow the appliance listing and Section 919.4.2(1) instead of installing a hood. Verify listing documentation before relying on that exception.
Related provisions (read next)
- § 921.1 — Open‑top broiler unit application/listing requirements.
- § 921.2 — Protection above domestic open‑top broiler units (hood thickness, clearances, hood sizing).
- § 921.3 — Commercial units — ventilation per Chapter 5, Part II.
- § 508.0 — Type I hoods: Where required and general hood rules (Chapter 5).
- § 508.5.1.2–508.5.1.5 — Hood airflow tables for extra‑heavy, heavy, medium, and light‑duty appliances (cf. broiler duty levels).
- § 509.0 – § 509.2.2 — Grease removal devices, vertical distances and protection requirements.
- Section 919.4.2(1) — Listing/installation exceptions referenced by § 921.2 for integral exhaust units.
Code references
Grounded in the retrieved California Mechanical Code — click a citation to read the verbatim passage:
CMC § 6.4 High relevance — show source text
(1) The underside of the combustible material or metal cabinet above the cooking top is protected with not less than [1] ⁄ 4 of an inch (6.4 mm) insulating millboard covered with sheet metal not less than 0.0122 of an inch (0.3099 mm) thick.
(2) A metal ventilating hood of sheet metal not less than 0.0122 of an inch (0.3099 mm) thick is installed above the cooking top with a clearance of not less
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than [1] ⁄ 4 of an inch (6.4 mm) between the hood and the underside of the combustible material or metal
cabinet, and the hood not less than the width of the appliance and is centered over the appliance.
(3) A listed cooking appliance or microwave oven installed over a listed cooking appliance shall be in accordance with the terms of the upper appliance’s listing and the manufacturer’s installation instructions. Microwave ovens shall comply with UL 923.
919.6 Level Installation. Cooking appliances shall be installed so that the cooking top, broiler pan, or oven racks are level. [NFPA 54-2018:10.14.3]
920.0 Cooking Appliance Listings.
920.1 Commercial Electric Ranges. Commercial electric ranges shall comply with UL 197 and installed in accordance with the manufacturer’s installation instructions.
920.2 Commercial Wood-Fired Baking Ovens. Commercial wood-fired baking ovens (refractory type) shall comply with UL 2162 and installed in accordance with the manufacturer’s installation instructions.
920.3 Oil-Burning Ranges. Oil-burning ranges shall comply with UL 896 and installed in accordance with the manufacturer’s installation instructions.
921.0 Open-Top Broiler Units.
921.1 Application. Open-top broiler units shall be listed in accordance with ANSI Z83.11/CSA 1.8 or ANSI/CSA
Z21.1/CSA 1.1 and installed in accordance with the manu facturer’s installation instructions. [NFPA 54:10.17.1]
921.2 Protection Above Domestic Units. Domestic opentop broiler units shall be provided with a metal ventilating hood not less than 0.0122 of an inch (0.3099 mm) thick with a clearance of not less than [1] ⁄ 4 of an inch (6.4 mm) between the hood and the underside of combustible material or metal cabinets. A
clearance of at least 24 inches (610 mm) shall be maintained between the cooking top and the combustible material or metal cabinet, and the hood shall be at least as wide as the open-top broiler unit and centered over the unit. Domestic open-top broiler units incorporating an integral exhaust system and listed for use without a ventilating hood shall not be required to be provided with a ventilating hood if installed in accordance with Section 919.4.2(1). [NFPA 54:10.17.2]
921.3 Commercial Units. Commercial open-top broiler units shall be provided with ventilation in accordance with Chapter 5, Part II. {NFPA 54:10.17.3}
922.0 Outdoor Cooking Appliances.
CMC § 920.3 High relevance — show source text
920.3 Oil-Burning Ranges. Oil-burning ranges shall comply with UL 896 and installed in accordance with the manufacturer’s installation instructions.
921.0 Open-Top Broiler Units.
921.1 Application. Open-top broiler units shall be listed in accordance with ANSI Z83.11/CSA 1.8 or ANSI/CSA
Z21.1/CSA 1.1 and installed in accordance with the manu facturer’s installation instructions. [NFPA 54:10.17.1]
921.2 Protection Above Domestic Units. Domestic opentop broiler units shall be provided with a metal ventilating hood not less than 0.0122 of an inch (0.3099 mm) thick with a clearance of not less than [1] ⁄ 4 of an inch (6.4 mm) between the hood and the underside of combustible material or metal cabinets. A
clearance of at least 24 inches (610 mm) shall be maintained between the cooking top and the combustible material or metal cabinet, and the hood shall be at least as wide as the open-top broiler unit and centered over the unit. Domestic open-top broiler units incorporating an integral exhaust system and listed for use without a ventilating hood shall not be required to be provided with a ventilating hood if installed in accordance with Section 919.4.2(1). [NFPA 54:10.17.2]
921.3 Commercial Units. Commercial open-top broiler units shall be provided with ventilation in accordance with Chapter 5, Part II. {NFPA 54:10.17.3}
922.0 Outdoor Cooking Appliances.
922.1 Application. Outdoor cooking appliances shall be listed in accordance with ANSI Z83.11/CSA 1.8, ANSI Z21.58/CSA 1.6, or ANSI Z21.89/CSA 1.18, and installed in accordance with the manufacturer’s installation instructions.
[NFPA 54:10.18]
210 2025 CALIFORNIA MECHANICAL CODE
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INSTALLATION OF SPECIFIC APPLIANCES
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923.0 Illuminating Appliances.
923.1 Clearances for Listed Appliances. Listed illuminating appliances shall be installed in accordance with their listing and the manufacturer’s installation instructions. {NFPA 54:10.14.1}
923.2 Clearances for Unlisted Appliances. Clearances for unlisted illuminating appliances shall comply with the following:
(1) Unlisted enclosed illuminating appliances installed outdoors shall be installed with clearances in any direction from combustible material of not less than 12 inches (305 mm). [NFPA 54:10.14.2.1(1)]
(2) Unlisted enclosed illuminating appliances installed indoors shall be installed with clearances in any direction from combustible material of not less than 18 inches
(457 mm). [NFPA 54:10.14.2.1(2)]
923.2.1 Open-Flame Type. Clearance shall comply with the following:
CMC § 919.0 High relevance — show source text
919.0 Household Cooking Appliances. . . 209
919.1 Application . . . . . . . . . . . . . . . . . . 209
919.2 Electric Household Cooking Appliances . . . . . . . . . . . . . . . . . . 209
919.3 Gas-Fired Household Cooking Appliances . . . . . . . . . . . . . . . . . . 209
919.4 Floor-Mounted Units . . . . . . . . . . . 210
919.5 Built-In Units . . . . . . . . . . . . . . . . . 210
919.6 Level Installation. . . . . . . . . . . . . . 210
920.0 Cooking Appliance Listings . . . . . 210
920.1 Commercial Electric Ranges . . . . 210
920.2 Commercial Wood-Fired
Baking Ovens . . . . . . . . . . . . . . . . 210
920.3 Oil-Burning Ranges . . . . . . . . . . . 210
921.0 Open-Top Broiler Units. . . . . . . . . 210
921.1 Application . . . . . . . . . . . . . . . . . . 210
921.2 Protection Above Domestic Units. . 210
2025 CALIFORNIA MECHANICAL CODE
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TABLE OF CONTENTS
921.3 Commercial Units . . . . . . . . . . . . . 210
922.0 Outdoor Cooking Appliances . . . . 210
922.1 Application . . . . . . . . . . . . . . . . . . 210
923.0 Illuminating Appliances. . . . . . . . . 211
923.1 Clearances for Listed Appliances. . 211
923.2 Clearances for Unlisted
Appliances . . . . . . . . . . . . . . . . . . 211
Table 923.2.1 Clearances for Unlisted Outdoor
Open-Flame Illuminating Appliances . . . . . . . . . . . . . . . . . . 211
923.3 Mounting on Buildings . . . . . . . . . 211
923.4 Mounting on Posts . . . . . . . . . . . . 211
923.5 Appliance Pressure Regulators . . . 211
924.0 Incinerators and Crematories . . . . 211
924.1 Field Constructed Commercial Industrial Incinerators . . . . . . . . . . 211
924.2 Factory-Built Commercial Crematories . . . . . . . . . . . . . . . . . 211
924.3 Residential Incinerators . . . . . . . . 211
925.0 Infrared Heaters . . . . . . . . . . . . . . 211
925.1 Application . . . . . . . . . . . . . . . . . . 211
925.2 Support . . . . . . . . . . . . . . . . . . . . . 211
925.3 Clearance . . . . . . . . . . . . . . . . . . . 211
925.4 Combustion and Ventilation Air . . . 212
925.5 Installation in Commercial
CMC § 916.7 Medium relevance — show source text
Garages and Aircraft Hangars . . . 208
916.7 Oil-Fired Unit Heaters. . . . . . . . . . 208
917.0 Food Service Appliance, FloorMounted . . . . . . . . . . . . . . . . . . . . 208
917.1 Application . . . . . . . . . . . . . . . . . . 208
917.2 Clearance for Listed Appliances. . . 208
917.3 Mounting on Combustible Floors . . . . . . . . . . . . . . . . . . . . . . 208
917.4 Installation on Noncombustible
Floors . . . . . . . . . . . . . . . . . . . . . . 209
917.5 Combustible Material
Adjacent to Cooking Top . . . . . . . 209
917.6 Use with Casters . . . . . . . . . . . . . 209
917.7 Level Installation. . . . . . . . . . . . . . 209
917.8 Ventilation. . . . . . . . . . . . . . . . . . . 209
918.0 Food Service Appliances, Counter Appliances . . . . . . . . . . . 209
918.1 Application . . . . . . . . . . . . . . . . . . 209
918.2 Vertical Clearance . . . . . . . . . . . . 209
918.3 Clearance for Listed Appliances. . . 209
918.4 Clearance for Unlisted
Appliances . . . . . . . . . . . . . . . . . . 209
919.0 Household Cooking Appliances. . . 209
919.1 Application . . . . . . . . . . . . . . . . . . 209
919.2 Electric Household Cooking Appliances . . . . . . . . . . . . . . . . . . 209
919.3 Gas-Fired Household Cooking Appliances . . . . . . . . . . . . . . . . . . 209
919.4 Floor-Mounted Units . . . . . . . . . . . 210
919.5 Built-In Units . . . . . . . . . . . . . . . . . 210
919.6 Level Installation. . . . . . . . . . . . . . 210
920.0 Cooking Appliance Listings . . . . . 210
920.1 Commercial Electric Ranges . . . . 210
920.2 Commercial Wood-Fired
Baking Ovens . . . . . . . . . . . . . . . . 210
920.3 Oil-Burning Ranges . . . . . . . . . . . 210
921.0 Open-Top Broiler Units. . . . . . . . . 210
921.1 Application . . . . . . . . . . . . . . . . . . 210
921.2 Protection Above Domestic Units. . 210
2025 CALIFORNIA MECHANICAL CODE
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TABLE OF CONTENTS
921.3 Commercial Units . . . . . . . . . . . . . 210
922.0 Outdoor Cooking Appliances . . . . 210
CMC § 508.5.1.1 Medium relevance — show source text
508.5.1.1 Capacity of Hoods. Canopy-type commercial cooking hoods shall exhaust through the hood with a quantity of air not less than determined by the application in accordance with Section 508.5.1.2 through Section 508.5.1.5. The exhaust quantity shall be the net exhaust from the hood determined in accordance with Equation 508.5.1.1. The duty level for the hood shall be the duty level of the appliance that has the highest (heaviest) duty level of appliances installed underneath the hood.
Exception: Listed exhaust hoods installed in accordance with the manufacturer’s installation instruc tions.
E NET = E HOOD – MA ID (Equation 508.5.1.1)
112 2025 CALIFORNIA MECHANICAL CODE
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EXHAUST SYSTEMS
Where:
E NET = net hood exhaust, CFM.
E HOOD = total hood exhaust, CFM.
MA ID = makeup air, internal discharge, CFM.
For SI Units: 1 cubic foot per minute = 0.4719 L/s
508.5.1.2 Extra-Heavy-Duty Cooking Appli- ances. The minimum net airflow for hoods used for
solid fuel cooking appliances such as charcoal, briquette, and mesquite to provide the heat source for cooking shall be in accordance with Table 508.5.1.2.
TABLE 508.5.1.2
EXTRA-HEAVY-DUTY COOKING APPLIANCE AIRFLOW
TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)
Backshelf/pass-overNot permitted
Double island canopy (per side)550
EyebrowNot permitted
Single island canopy700
Wall-mounted canopy550 For SI units: 1 foot = 304.8 mm, 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s
508.5.1.3 Heavy-Duty Cooking Appliances. The minimum net airflow for hoods used for cook ing appliances such as gas under-fired broilers, gas chain (conveyor) broilers, electric and gas wok ranges, and electric and gas over-fired (upright) broilers shall be in accordance with Table 508.5.1.3.
TABLE 508.5.1.3
HEAVY-DUTY COOKING APPLIANCE AIRFLOW
TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)
Backshelf/pass-over400
Double island canopy (per side)400
EyebrowNot permitted
Single island canopy600
Wall-mounted canopy400 For SI units: 1 foot = 304.8 mm, 1 cubic foot per minute = 0.0283 m [3] /min,
1 cubic foot per minute = 0.4719 L/s
CMC § 506.11.6 Medium relevance — show source text
506.11.6 Reduced Clearance with Air Gaps. When using clearance reduction systems that include an air gap between the combustible surface and the selected means of protection, air circulation shall be provided by one of the methods in Section 506.11.6.1 through Section 506.11.6.3. [NFPA 91:4.7.4.7]
506.11.6.1 Air Circulation. Air circulation shall be permitted to be provided by leaving all edges of the protecting system open with at least a 1 inch (25.4 mm) air gap. [NFPA 91:4.7.4.7.1] 506.11.6.2 Single Flat Wall. If the means of protection is mounted on a single flat wall away from corners, air circulation shall be permitted to be provided by one of the following:
(1) Leaving only the top and bottom edges open to circulation by maintaining the 1 inch (25.4 mm) air gap.
(2) Leaving the top and both side edges open to circulation by maintaining the 1 inch (25.4 mm) air gap. [NFPA 91:4.7.4.7.2] 506.11.6.3 Thermal Shielding. Thermal shielding that covers two walls in a corner shall be permitted to be open at the top and bottom edges with at least 1 inch (25.4 mm) air gap. [NFPA 91:4.7.4.7.3]
TABLE 506.11
REDUCTION OF DUCT CLEARANCE WITH SPECIFIED FORMS OF PROTECTION
[NFPA 91: TABLE 4.7.4]
FORM OF PROTECTION* MAXIMUM ALLOWABLE REDUCTION IN CLEARANCE (percent) Col3 FORM OF PROTECTION* AS WALL PROTECTOR OR
VERTICAL SURFACEAS CEILING PROTECTOR OR
HORIZONTAL SURFACE31⁄2 inch thick masonry wall without ventilated air space 33 None 1⁄2 inch thick noncombustible insulation board over 1 inch glass fiber or min-
eral wool batts without ventilated air space50 33 0.024 inch (24 gauge) sheet metal over 1 inch glass fiber or mineral wool batts
reinforced with wire, or equivalent on rear face with at least a 1 inch air gap66 66 31⁄2 inch (90 mm) thick masonry wall with at least a 1 inch air gap 66 None 0.024 inch (24 gauge) sheet metal with at least a 1 inch air gap 66 50 1⁄2 inch thick noncombustible insulation board with at least a 1 inch air gap 66 50 0.024 inch (24 gauge) sheet metal with ventilated air space over at least
0.024 inch (24 gauge) sheet metal with at least a 1 inch air gap66 50 1 inch glass fiber or mineral wool batts sandwiched between two sheets of
0.024 inch (24 gauge) sheet metal with at least a 1 inch air gap66 50 For SI units: 1 inch = 25.4 mm
- Clearance reduction applied to and covering all combustible surfaces within the distance specified as required clearance with no protection in Table 506.10.4.
108 2025 CALIFORNIA MECHANICAL CODE
CMC § 304.8 Medium relevance — show source text
TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)
Backshelf/pass-overNot permitted
Double island canopy (per side)550
EyebrowNot permitted
Single island canopy700
Wall-mounted canopy550 For SI units: 1 foot = 304.8 mm, 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s
508.5.1.3 Heavy-Duty Cooking Appliances. The minimum net airflow for hoods used for cook ing appliances such as gas under-fired broilers, gas chain (conveyor) broilers, electric and gas wok ranges, and electric and gas over-fired (upright) broilers shall be in accordance with Table 508.5.1.3.
TABLE 508.5.1.3
HEAVY-DUTY COOKING APPLIANCE AIRFLOW
TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)
Backshelf/pass-over400
Double island canopy (per side)400
EyebrowNot permitted
Single island canopy600
Wall-mounted canopy400 For SI units: 1 foot = 304.8 mm, 1 cubic foot per minute = 0.0283 m [3] /min,
1 cubic foot per minute = 0.4719 L/s
508.5.1.4 Medium-Duty Cooking Appliances. The minimum net airflow for hoods used for cooking appliances such as electric and gas hot-top ranges, gas open-burner ranges (with or without oven), elec
TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)
Backshelf/pass-over300
Double island canopy (per side)300
Eyebrow250
Single island canopy500
Wall-mounted canopy300 TABLE 508.5.1.5
LIGHT-DUTY COOKING APPLIANCE AIRFLOW
TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)
Backshelf/pass-over250 Double island canopy (per side) 250
Eyebrow250
Single island canopy400
Wall-mounted canopy200 For SI units: 1 foot = 304.8 mm, 1 cubic foot per minute = 0.0283 m [3] /min,
1 cubic foot per minute = 0.4719 L/s
508.5.2 Noncanopy-Type Hoods. Noncanopy-type commercial cooking hoods shall be installed and sized in accordance with the manufacturer’s installation instruc tions, and Section 508.5.2.1 and Section 508.5.2.2.
Exception: Listed hood assemblies designed and installed specifically for the intended use.
CMC § 4.6.4 Medium relevance — show source text
EXHAUST SYSTEMS
copies of operating instructions for subassemblies and components used in the exhaust system, including electrical schematics, shall be kept on the premises and made available on request to the Authority Having Jurisdiction and maintenance persons. [NFPA 96:4.6.4]
507.6 Notification of Change. If required by the Authority Having Jurisdiction, notification in writing shall be given of any alteration, replacement, or relocation of any exhaust or extinguishing system or part thereof or cooking equipment.
[NFPA 96:4.7]
Satisfaction shall be provided to the Authority Having Jurisdiction that the complete exhaust system as addressed in this chapter is installed and operable in accordance with the approved design and the manufacturer’s installation instructions.
507.7 Pharmaceutical Compounding Exhaust Dis- charge. [OSHPD 1, 2, 3, 4 & 5] Exhaust discharge from fans serving the compounding suite shall extend at least 7 feet (2134 mm) above the roof and discharge vertically upward. Self-draining stacks or equivalent shall be used for rain pro- tection. Rain caps which divert the exhaust toward the roof shall be prohibited.
508.0 Type I Hoods.
508.1 Where Required. Type I hoods shall be installed at or above commercial-type deep-fat fryers, broilers, grills, hottop ranges, ovens, barbecues, rotisseries, and similar equipment that emits comparable amounts of smoke or grease in a food-processing establishment. For the purpose of this section, a food-processing establishment shall include a building or portion thereof used for the processing of food, but shall not include a dwelling unit.
Exceptions:
(1) A Type I hood shall not be required for cooking appliances that comply with UL 197 for reduced emissions where the grease discharge does not exceed 2.9 E-09 ounces per cubic inch (oz/in [3] ) (5.0 E-06 kg/m [3] ) where operated with a total airflow of 500 cubic feet per minute (CFM) (236 L/s).
(2) Recirculating systems listed in accordance with UL 710B and installed in accordance with Section 516.0.
(3) Solid-fuel-fired ovens that comply with UL 2162 and that are vented in accordance with the manufacturer’s
instructions with venting systems complying with UL 103 and UL 1978.
(4) Listed and labeled cooking appliances with integral downdraft systems that comply with Section 518.0.
508.2 Listed Type I Hood Assemblies. Listed hood assemblies shall be installed in accordance with the terms of
their listing and the manufacturer’s instructions. Listed hood assemblies shall be tested in accordance with UL 710 or
equivalent. {NFPA 96:5.4.1, 5.4.2}
508.2.1 Listed Ultraviolet Hoods. Listed ultraviolet
hoods shall be installed and maintained in accordance
with the terms of their listing and the manufacturer’s instructions. Duct systems connected to ultraviolet hoods shall comply with Section 510.0. Ultraviolet hoods shall be tested and listed in accordance with UL 710. {NFPA 96:5.5 – 5.5.2}
508.2.2 Listed Ventilated Ceiling Technology. Listed ventilated ceiling technology shall be installed and maintained in accordance with the terms of its listing and the manufacturer's instructions. [NFPA 96:5.6]
CMC § 420.6.2 Medium relevance — show source text
Exception: Spaces having a direct exit to a public way.
420.6.2 Refuge area. Refuge areas shall be provided within each smoke compartment. The size of the refuge area shall accommodate the occupants and care recipients from the adjoining smoke compartment. Where a smoke compartment is adjoined by two or more smoke compartments, the minimum area of the refuge area shall accommodate the largest occupant load of the adjoining compartments. The size of the refuge area shall provide the following:
- Not less than 15 net square feet (1.4 m [2] ) for each care recipient.
- Not less than 6 net square feet (0.56 m [2] ) for other occupants.
Areas or spaces permitted to be included in the calculation of the refuge area are corridors, lounge or dining areas and other low-hazard areas.
420.7 Reserved.
420.8 Reserved.
420.9 Domestic cooking appliances. In Group R-2.1 occupancies, installation of cooking appliance used in domestic cooking facilities shall comply with all of the following:
- The types of cooking appliances permitted shall be limited to ovens, cooktops, ranges, warmers and microwaves.
- Domestic cooking hoods installed and constructed in accordance with the California Mechanical Code shall be provided over cooktops or ranges.
- Cooktops and ranges shall be protected in accordance with Section 904.15.
- A shutoff for the fuel and electrical supply to the cooking equipment shall be provided in a location to which only staff has
access.
A timer shall be provided that automatically deactivates the cooking appliances within a period of not more than 120 minutes.
A portable fire extinguisher shall be provided. Installation shall be in accordance with Section 906 and the extinguisher shall be located within a 30-foot (9144 mm) distance of travel from each domestic cooking appliance.
Exceptions:
- Cooking facilities provided within care recipients’ individual dwelling units are not required to comply with this section.
- Cooktops and ranges used for care-recipient training or nutritional counseling are not required to comply with Item 3 of this section.
420.10 Group R cooking facilities. In Group R occupancies, cooking appliances used for domestic cooking operations shall be in accordance with the California Mechanical Code .
420.11 Group R-2 dormitory cooking facilities. Domestic cooking appliances for use by residents of Group R-2 college dormitories shall be in accordance with Sections 420.11.1 and 420.11.2.
420.11.1 Cooking appliances. Where located in Group R-2 college dormitories, domestic cooking appliances for use by residents shall be in compliance with all of the following:
The types of domestic cooking appliances shall be limited to ovens, cooktops, ranges, warmers, coffee makers and microwaves.
Domestic cooking appliances shall be limited to approved locations.
Cooktops and ranges shall be protected in accordance with Section 904.15.
Cooktops and ranges shall be provided with a domestic cooking hood installed and constructed in accordance with the California Mechanical Code . Kitchen range hoods shall also be rated for sound and meet field verification requirements in the California Energy Code for low-rise and high-rise residential buildings.
420.11.2 Cooking appliances in sleeping rooms. Cooktops, ranges and ovens shall not be installed or used in sleeping rooms.
CMC § 519.1 Medium relevance — show source text
519.1 Where Required. Type II hoods shall be installed above equipment and dishwashers that generate steam, heat, or products of combustion, and where grease or smoke is not present.
Exceptions:
(1) Dishwashing machines connected to a Type II duct system and exhausted directly to the outdoors.
(2) Dishwashing machines with a self-contained condensing system listed in accordance with UL 921 and installed in a space where the HVAC system has been engineered to accommodate the latent and sensible heat load emitted from such appliances as approved by the Authority Having Jurisdiction. Such equipment shall be provided with an interlocking device to prevent opening of the appliance prior to completion of its cycle. 519.2 Construction of Type II Hoods. Type II hoods constructed of steel shall be not less than 0.024 of an inch (0.61 mm) (No. 24 gauge). Hoods constructed of copper shall be of copper sheets weighing not less than 0.17 ounces per square inch (oz/in [2] ) (7.47 kg/m [2] ). Joints and seams shall be substantially tight. Solder shall not be used except for sealing a joint or seam. 519.3 Type II Hood Exhaust System Net Airflow. The net airflow for Type II hoods shall be in accordance with Section 508.5.1.5 for light-duty cooking appliances. The net airflow for Type II hoods serving dishwashing appliances shall comply with Section 519.3.1.
519.3.1 Dishwashing Appliances. The net airflow for Type II hoods used for dishwashing equipment shall be not less than 200 cubic feet per minute (0.094 m [3] /s) per linear foot (m) of hood length.
519.4 Type II Exhaust Duct Systems. Ducts and plenums serving Type II hoods shall be constructed of rigid metallic materials in accordance with Chapter 6. Duct bracing and supports shall comply with Chapter 6. Ducts subject to positive pressure shall be adequately sealed.
519.5 Termination of Type II Hood Exhaust System. The exhaust system shall terminate in accordance with Section 502.2.2. Rooftop terminations shall be directed away
«
132 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
EXHAUST SYSTEMS
from roof surfaces within 40 inches (1016 mm). The discharge outlet of moisture conveying exhaust ducts, such as dishwasher exhaust ducts, shall not terminate over a public way or over an area where condensate or vapor could create a nuisance or hazard.
519.6 Makeup Air. Makeup air shall be provided in accordance with Section 511.3.
519.7 Independent Exhaust Duct System. Single or combined Type II exhaust systems shall be independent of all other exhaust systems.
2025 CALIFORNIA MECHANICAL CODE 133
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
134 2025 CALIFORNIA MECHANICAL CODE
), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
CALIFORNIA MECHANICAL CODE – MATRIX ADOPTION TABLE
CHAPTER 6 – DUCT SYSTEMS
California Mechanical Code Medium relevance — show source text
r>1000
959
921
888|1890
1800
1730
1660
1600|2980
2840
2720
2620
2520|6210
5920
5670
5450
5250| |800
850
900
950
1000|800
850
900
950
1000|39
37
36
35
34|80
77
75
72
71|162
157
152
147
143|283
274
265
258
251|401
388
376
366
356|857
829
804
781
760|1540
1490
1450
1410
1370|2430
2350
2280
2220
2160|5070
4900
4750
4620
4490| |1100
1200
1300
1400
1500|1100
1200
1300
1400
1500|32
31
30
28
27|67
64
61
59
57|136
130
124
120
115|238
227
217
209
201|338
322
309
296
286|721
688
659
633
610|1300
1240
1190
1140
1100|2050<
Frequently asked questions
Can I install a domestic open-top broiler without a hood if it has an exhaust fan built in?
Only if the broiler is listed for use without a ventilating hood and is installed exactly per the manufacturer’s instructions and per Section 919.4.2(1); otherwise § 921.2 requires a metal hood and the stated clearances.
What is the minimum thickness for a domestic hood?
The hood must be not less than 0.0122 inches (0.3099 mm) thick as required by § 921.2.
How far must the cooking top be from combustible cabinets above?
Maintain at least 24 inches (610 mm) between the cooking top and combustible material or cabinet for domestic open‑top broilers unless another protection/listing permits a different arrangement — see § 921.2.
Do commercial broilers use the same hood details as residential?
No. Commercial open‑top broilers are governed by Chapter 5, Part II (Type I hood rules, airflow, grease filters, ductwork, makeup air). You must design per those commercial hood provisions (see § 921.3 and § 508.0).
Are mesh grease filters allowed in commercial hoods?
Mesh filters are not permitted unless evaluated and listed as an integral part of a listed exhaust hood or used in conjunction with a listed primary filter per § 509.1.1.
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