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Chapter 5 — EXHAUST SYSTEMS

508.5 Hood Size. Hoods shall be sized in accordance with

California Mechanical Code (Title 24, Part 4) · 2022 edition · updated 2026-09-10 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

the airflow capacity in accordance with Section 508.5.1.1 and installed to provide for the removal of heat, and capture and removal of grease-laden vapors in accordance with Section 511.2.2. 508.5.1 Canopy Size and Location. For canopy type commercial cooking hoods, the inside edge thereof shall overhang or extend a horizontal distance of not less than 6 inches (152 mm) beyond the edge of the cooking surface on open sides, and the vertical distance between the lip of the hood and the cooking surface shall not exceed 4 feet (1219 mm). Exception: Listed exhaust hoods are to be installed in accordance with the terms of their listings and the manufacturer’s installation instructions.

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 instructions.

ENET = EHOOD - MAID (Equation 508.5.1.1)

Where: ENET = net hood exhaust EHOOD = total hood exhaust MAID = makeup air, internal discharge

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-over
Not permitted

Double island canopy (per side)
550

Eyebrow
Not permitted

Single island canopy
700

Wall-mounted canopy
550

For SI units: 1 cubic foot per minute = 0.00047 m 3 /s, 1 foot = 304.8 mm

508.5.1.3 Heavy-Duty Cooking Appliances. The minimum net airflow for hoods used for cooking 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-over
400

Double island canopy (per side)
400

Eyebrow
Not permitted

Single island canopy
600

Wall-mounted canopy
400

For SI units: 1 cubic foot per minute = 0.00047 m 3 /s, 1 foot = 304.8 mm

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), electric and gas flat griddles, electric and gas doublesided griddles, electric and gas fryers (including open deep fat fryers, donut fryers, kettle fryers, and pressure fryers), and electric and gas conveyor pizza ovens shall be in accordance with Table 508.5.1.4.

TABLE 508.5.1.4 MEDIUM-DUTY COOKING APPLIANCE AIRFLOW

TYPE OF HOOD AIRFLOW (cubic foot per minute
per linear foot of hood)

Backshelf/pass-over
300

Double island canopy (per side)
300

Eyebrow
250

Single island canopy
500

Wall-mounted canopy
300

For SI units: 1 cubic foot per minute = 0.00047 m 3 /s, 1 foot = 304.8 mm

100 2022 CALIFORNIA MECHANICAL CODE

508.5.1.5 Light-Duty Cooking Appliances. The minimum net airflow for hoods used for cooking appliances such as gas and electric ovens (including standard, bake, roasting, revolving, retherm, convection, combination convection/steamer, rotisserie, countertop conveyorized baking/finishing, deck, and pastry), discrete element ranges (with or without oven), electric and gas steam-jacketed kettles less than 20 gallons (76 L), electric and gas pasta cookers, electric and gas compartment steamers (both pressure and atmospheric), electric and gas cheese melters, electric and gas tilting skillets (braising pans) electric and gas rotisseries, and electric and gas salamanders shall be in accordance with Table 508.5.1.5.

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-over
250

Double island canopy (per side)
250

Eyebrow
250

Single island canopy
400

Wall-mounted canopy
200

For SI units: 1 cubic foot per minute = 0.00047 m 3 /s, 1 foot = 304.8 mm

508.5.2 Noncanopy-Type Hoods. Noncanopy-type commercial cooking hoods shall be installed and sized in accordance with the manufacturer’s installation instructions, and Section 508.5.2.1 and Section 508.5.2.2. Exception: Listed hood assemblies designed and installed specifically for the intended use.

508.5.2.1 Installation. Noncanopy-type commercial cooking hoods shall be installed with the edge of the hood set back not more than 1 foot (305 mm) from the edge of the cooking surface, and the vertical distance between the lip of the hood and the cooking surface shall not exceed 3 feet (914 mm). 508.5.2.2 Capacity. In addition to other requirements for hoods specified in this section, the volume of air exhausting through a noncanopy-type hood to the duct system shall be not less than 300 cubic feet per minute per lineal foot [(ft 3 /min)/ft)] [0.464 (m 3 /s)/m] of cooking equipment. Listed noncanopy exhaust hoods and filters shall be sized and installed in accordance with the terms of their listing and the manufacturer’s installation instructions. 508.5.3 Labeling. Type I hoods shall bear a label indicating the exhaust flow rate in cubic feet per minute per lineal foot [(m 3 /s)/m].

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Contents — California Mechanical Code (Title 24, Part 4)
California Mechanical Code (Title 24, Part 4)
  1. Chapter 1 — GENERAL CODE PROVISIONS
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — GENERAL REGULATIONS
  4. Chapter 4 — VENTILATION AIR
  5. Chapter 5 — EXHAUST SYSTEMS
    Overview
    1. 501.1 Applicability. This chapter includes requirements for
    2. 502.1 Exhaust Opening Protection. Exhaust openings
    3. 502.2 Termination of Exhaust Ducts. Exhaust ducts
    4. 503.1 General. Motors and fans shall be sized to provide
    5. 503.2 Fans. Parts of fans in contact with explosive or flammab…
    6. 504.1 General. Where not specified in this chapter, exhaust
    7. 504.2 Independent Exhaust Systems. Single or combined mechanic…
    8. 504.3 Domestic Range. Ducts used for domestic kitchen
    9. 504.4 Clothes Dryers. A clothes dryer exhaust duct shall not
    10. 504.5 Heat (Energy) Recovery Ventilators. Heat
    11. 504.6 Gypsum Wallboard Ducts. Bathroom and laundry
    12. 505.1 General. A mechanical ventilation or exhaust system
    13. 505.2 Incompatible Materials. Incompatible materials
    14. 505.3 Flammability Limit. Unless the circumstances stipulated …
    15. 505.4 Air-Moving Devices. Air-moving devices shall be
    16. 505.5 Generating Flames, Sparks, or Hot Materials.
    17. 505.6 Fire Dampers. Fire dampers shall be permitted to be
    18. 505.7 Fire Detection and Alarm Systems. Unless the
    19. 505.8 Product-Conveying Ducts Classification. Product-conveyin…
    20. 505.9 Minimum Velocities and Circulation. The velocity and cir…
    21. 505.10 Makeup Air. Makeup air shall be provided to replenish a…
    22. 505.11 Hoods and Enclosures. Hoods and enclosures shall
    23. 505.12 Pharmacies – Compounding Area of Par-
    24. 506.1 Materials. Materials used in product-conveying duct
    25. 506.2 Construction. Ducts used for conveying products
    26. 506.3 Penetrations. Exhaust ducts shall not pass through
    27. 506.4 Condensate. Joints in duct construction shall be liquidt…
    28. 506.5 Fittings. Fittings in Class 2, 3, and 4 systems shall be
    29. 506.6 Explosion Venting. Ducts conveying explosive dusts
    30. 506.7 Supports. Supports shall be of noncombustible materials,…
    31. 506.8 Fire Protection. Sprinklers or other fire-protection
    32. 506.9 Protection from Physical Damage. Ducts
    33. 506.10 Duct Clearances. Unless the conditions stipulated
    34. 506.11 Clearance Reduction Methods. It shall be permitted to p…
    35. 507.1 Type I Hood Exhaust System. Exhaust systems
    36. 507.2 Exhaust System. Cooking equipment used in
    37. 507.3 Listed Devices. Penetrations shall be sealed with
    38. 507.4 Clearance. Where enclosures are not required, hoods,
    39. 507.5 Drawings. A drawing(s) of the exhaust system installatio…
    40. 507.6 Notification of Change. If required by the Authority Hav…
    41. 507.7 Pharmaceutical Compounding Exhaust Dis-
    42. 508.1 Where Required. Type I hoods shall be installed at
    43. 508.2 Listed Type I Hood Assemblies. Listed hood
    44. 508.3 Construction of Type I Hoods. The hood or that
    45. 508.4 Supports. Hoods shall be secured in place [OSHPD
    46. 508.5 Hood Size. Hoods shall be sized in accordance with
    47. 508.6 Solid-Fuel Hood Assemblies. Where solid-fuel
    48. 508.7 Exhaust Outlets. An exhaust outlet within an
    49. 509.1 Grease Removal Devices. Listed grease filters or
    50. 509.2 Installation. The distance between the grease removal
    51. 509.3 Solid-Fuel Grease Removal Devices. Where
    52. 510.1 General. Ducts shall not pass through fire walls.
    53. 510.2 Clearance. Clearance between ducts and combustible
    54. 510.3 Openings. Openings shall be provided at the sides or
    55. 510.4 Listed Grease Ducts. Listed grease ducts shall be
    56. 510.5 Other Grease Ducts. Other grease ducts shall comply with…
    57. 510.6 Exterior Installations. The exterior portion of the
    58. 510.7 Interior Installations. In all buildings more than one
    59. 510.8 Underground Installations. Grease ducts installed
    60. 510.9 Termination of Type I Hood Exhaust System.
    61. 510.10 Solid-Fuel Duct Systems. Where solid-fuel cooking equip…
    62. 511.1 Exhaust Fans for Commercial Cooking Opera-
    63. 511.2 Airflow. The air velocity through a duct shall be not
    64. 511.3 Makeup Air. The makeup air quantity shall prevent
    65. 511.4 Common Duct (Manifold) Systems. Master
    66. 511.5 Solid-Fuel Air Movement Requirements. Where
    67. 512.1 Dampers. Dampers shall not be installed in exhaust
    68. 512.2 Electrical Equipment. Wiring systems of any type
    69. 512.3 Other Equipment. Fume incinerators, thermal recovery uni…
    70. 512.4 Solid-Fuel Auxiliary Equipment. Where solid fuel
    71. 513.1 General. Fire-extinguishing equipment for the protection…
    72. 513.2 Types of Equipment. Fire-extinguishing equipment
    73. 513.3 Simultaneous Operation. Fixed pipe extinguishing
    74. 513.4 Fuel and Electric Power Shutoff. Upon activation of
    75. 513.5 Manual Activation. All systems shall have both automatic…
    76. 514.2 Inspection, Testing, and Maintenance. Maintenance of the…
    77. 513.6 System Annunciation. Upon activation of an automatic fir…
    78. 513.7 Special Design and Application. Hoods containing
    79. 513.8 Review and Certification. Where required, complete
    80. 513.9 Installation Requirements. Installation of systems
    81. 513.10 Portable Fire Extinguishers. Portable fire extinguisher…
    82. 513.11 Maintenance. Portable fire extinguishers shall be
    83. 513.12 Solid-Fuel Fire-Extinguishing Equipment.
    84. 514.1 Operating Procedures. Exhaust systems shall be
    85. 514.3 Inspection for Grease Buildup. The entire exhaust
    86. 514.4 Cleaning of Exhaust Systems. If, upon inspection,
    87. 514.5 Cooking Equipment Maintenance. Inspection and
    88. 515.1 Cooking Equipment. Cooking equipment shall be
    89. 515.2 Operating Controls. Deep-fat fryers shall be equipped
    90. 516.1 General Requirements. Recirculating systems containing o…
    91. 516.2 Design Restrictions. All recirculating systems shall
    92. 516.3 Interlocks. The recirculating system shall be provided
    93. 516.4 Location and Application Restrictions. The
    94. 516.5 Additional Fire Safety Requirements. In addition to the …
    95. 516.6 Use and Maintenance. Automatic or manual covers on cooki…
    96. 517.1 Venting Application. Venting requirements of solidfuel c…
    97. 517.2 Location of Appliances. Every appliance shall be
    98. 517.3 Hoods for Solid-Fuel Cooking. Hoods shall be sized
    99. 517.4 Exhaust Systems for Solid-Fuel Cooking. Where
    100. 517.5 Grease Removal Devices for Solid-Fuel Cook-
    101. 517.6 Air Movement for Solid-Fuel Cooking. Exhaust
    102. 517.7 Fire-Extinguishing Equipment for Solid-Fuel
    103. 517.8 Other Safety Requirements. Metal-fabricated solidfuel co…
    104. 518.1 General. Downdraft appliance ventilation system
    105. 518.2 Ventilation System. The downdraft appliance ventilation …
    106. 518.3 Fire-Extinguishing Equipment. For fire-extinguishing equ…
    107. 518.4 Airflow Switch or Transducer. An airflow switch or
    108. 518.5 Surface Materials. Any surface located directly
    109. 519.1 Where Required. Type II hoods shall be installed
    110. 519.2 Construction of Type II Hoods. Type II hoods
    111. 519.3 Dishwashing Appliances. The net airflow for Type
    112. 519.4 Type II Exhaust Duct Systems. Ducts and
    113. 519.5 Termination of Type II Hood Exhaust System.
    114. 519.6 Makeup Air. Makeup air shall be provided in accordance w…
  6. Chapter 6 — DUCT SYSTEMS
  7. Chapter 7 — COMBUSTION AIR
  8. Chapter 8 — CHIMNEYS AND VENTS
  9. Chapter 9 — INSTALLATION OF SPECIFIC APPLIANCES
  10. Chapter 10 — BOILERS AND PRESSURE VESSELS
  11. Chapter 11 — REFRIGERATION
  12. Chapter 12 — HYDRONICS
  13. Chapter 13 — FUEL GAS PIPING
  14. Chapter 14 — PROCESS PIPING
  15. Chapter 15 — SOLAR ENERGY SYSTEMS
  16. Chapter 16 — STATIONARY POWER PLANTS
  17. Chapter 17 — REFERENCED STANDARDS
  18. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  19. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  20. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  21. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  22. Appendix E — SUSTAINABLE PRACTICES
  23. Appendix F — GEOTHERMAL ENERGY SYSTEMS
  24. Appendix G — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  25. Appendix H — EXAMPLE CALCULATION OF OUTDOOR AIR RATE

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