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Earlier editions: 20222019

Chapter 5 — EXHAUST SYSTEMS

California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-10 · California

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

(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 BSC BSC-
CG		 SFM HCD DSA OSHPD BSCC DPH AGR DWR CEC CA SL SLC
Adopting Agency BSC BSC-
CG		 SFM 1 2 1-AC AC ** SS** ** SS/CC** 1 1R 2 3 4 5 6 6 6 6 6 6 6 6 6
Adopt Entire Chapter X X X X X X
Adopt Entire Chapter as
amended (amended sections
listed below)		 X X X X X X X
Adopt only those sections
that are listed below		 X
Chapter/Section
504.1.1 X X X X X
505.7.3 X
505.12 X
505.12.1 X
507.7 X X X X X
508.4 X X X X X
509.2.3 X
509.2.3.4 X
513.2.2 X
513.2.2 Exception 2 X X
513.3.5 X
513.10 X
513.10.1 X

This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

98 2025 CALIFORNIA MECHANICAL CODE

CHAPTER 5

EXHAUST SYSTEMS

502.2.4 Commercial Kitchen Ducts. Commercial

kitchens exhaust ducts shall terminate in accordance with

Section 510.9 for Type I exhaust systems or Section 519.5 for Type II exhaust systems.

Part I – Environmental Air Ducts and Product-Conveying Systems.

503.0 Motors, Fans, and Filters.

504.0 Environmental Air Ducts.

501.0 General.

502.0 Termination.

505.0 Product-Conveying Systems.

506.0 Product-Conveying Ducts.

507.0 General Requirements.

508.0 Type I Hoods.

509.0 Grease Removal Devices in Hoods.

510.0 Exhaust Duct Systems.

511.0 Air Movement.

512.0 Auxiliary Equipment.

513.0 Fire-Extinguishing Equipment.

514.0 Procedures for the Use, Inspection, Testing, and

Maintenance of Equipment.

515.0 Minimum Safety Requirements for Cooking

Equipment.

516.0 Recirculating Systems.

517.0 Solid-Fuel Cooking Operations.

518.0 Downdraft Appliances.

519.0 Type II Hood Exhaust System Requirements.

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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. 503.1 General. Motors and fans shall be sized to provide
    2. 503.2 Fans. Parts of fans in contact with explosive or flammab…
    3. 504.1 General. Where not specified in this chapter, exhaust
    4. 501.1 Applicability. This chapter includes requirements for
    5. 502.1 Exhaust Opening Protection. Exhaust openings
    6. 502.2 Termination of Exhaust Ducts. Exhaust ducts
    7. 504.2 Independent Exhaust Systems. Single or combined mechanic…
    8. 504.3 Domestic Cooking Exhaust Equipment.
    9. 504.4 Clothes Dryers. A clothes dryer exhaust duct shall
    10. 504.5 Heat Recovery Ventilation (HRV) and Energy
    11. 505.1 General. A mechanical ventilation or exhaust system
    12. 505.2 Incompatible Materials. Incompatible materials
    13. 505.3 Flammability Limit. Unless the circumstances stipulated …
    14. 505.4 Air-Moving Devices. Air-moving devices shall be
    15. 505.5 Generating Flames, Sparks, or Hot Materials.
    16. 505.6 Fire Dampers. Fire dampers shall be permitted to be
    17. 505.7 Fire Detection, Smoke Control, and Alarm Sys-
    18. 505.8 Product-Conveying Duct Classifications. Product-conveyin…
    19. 505.9 Minimum Velocities and Circulation. The velocity and cir…
    20. 505.10 Makeup Air. Makeup air shall be provided to replenish a…
    21. 505.11 Hoods and Enclosures. Hoods and enclosures shall
    22. 505.12 Pharmacies – Compounding Area of Par-
    23. 506.1 Materials. Materials used in product-conveying duct
    24. 506.2 Construction. Ducts used for conveying products
    25. 506.3 Penetrations. Exhaust ducts shall not pass through
    26. 506.4 Condensate. Joints in duct construction shall be liquidt…
    27. 506.5 Fittings. Fittings in Class 2, 3, and 4 systems shall be
    28. 506.6 Explosion Venting. Ducts conveying explosive dusts
    29. 506.7 Supports. Supports shall be of noncombustible materials,…
    30. 506.8 Fire Protection. Sprinklers or other fire-protection
    31. 506.9 Protection from Physical Damage. Ducts and
    32. 506.10 Duct Clearances. Unless the conditions stipulated
    33. 506.11 Clearance Reduction Methods. It shall be permitted to p…
    34. 507.1 Exhaust Systems. Exhaust systems serving Type I
    35. 507.2 Type I Hood Exhaust System Requirements.
    36. 507.3 Listed Devices. Penetrations shall be sealed with
    37. 507.4 Clearance. Where enclosures are not required, hoods,
    38. 507.5 Drawings. For cooking operations in buildings, a
    39. 507.6 Notification of Change. If required by the Authority Hav…
    40. 507.7 Pharmaceutical Compounding Exhaust Dis-
    41. 508.1 Where Required. Type I hoods shall be installed at
    42. 508.2 Listed Type I Hood Assemblies. Listed hood
    43. 508.3 Construction of Type I Hoods. The hood or that
    44. 508.4 Supports. Hoods shall be secured in place to resist
    45. 508.5 Hood Size. Hoods shall be sized in accordance with
    46. 508.6 Solid-Fuel Hood Assemblies. Where solid-fuel
    47. 508.7 Exhaust Outlets. An exhaust outlet within an
    48. 509.1 Grease Removal Devices. Listed grease filters or
    49. 509.2 Installation. The distance between the grease removal
    50. 509.3 Solid-Fuel Grease Removal Devices. Where
    51. 510.1 General. Ducts shall not pass through fire walls.
    52. 510.2 Clearance. Clearance between ducts and combustible
    53. 510.3 Openings. Openings shall be provided at the sides or
    54. 510.4 Listed Grease Ducts. Listed grease ducts shall be
    55. 510.5 Other Grease Ducts. Other grease ducts shall comply with…
    56. 510.6 Exterior Installations. For cooking operations in
    57. 510.7 Interior Installations. In all buildings more than one
    58. 510.8 Underground Installations. Grease ducts installed
    59. 510.9 Termination of Type I Hood Exhaust System.
    60. 510.10 Solid-Fuel Duct Systems. Where solid-fuel cooking equip…
    61. 511.1 Exhaust Fans for Commercial Cooking Opera-
    62. 511.2 Airflow. The air velocity through a duct shall be not
    63. 511.3 Makeup Air. The makeup air quantity shall prevent
    64. 511.4 Common Duct (Manifold) Systems. Master
    65. 511.5 Solid-Fuel Air Movement Requirements. Where
    66. 512.1 Dampers. Dampers shall not be installed in exhaust
    67. 512.2 Electrical Equipment. Wiring systems of any type
    68. 512.3 Other Equipment. Fume incinerators, thermal recovery uni…
    69. 512.4 Solid-Fuel Auxiliary Equipment. Where solid fuel
    70. 513.1 General. Fire-extinguishing equipment for the protection…
    71. 513.2 Types of Equipment. Fire-extinguishing equipment
    72. 513.3 Simultaneous Operation. Fixed pipe extinguishing
    73. 513.4 Fuel and Electric Power Shutoff. Upon actuation of
    74. 513.5 Manual Actuation. All systems shall have both automatic …
    75. 513.6 System Annunciation. Upon actuation of an automatic fire…
    76. 513.7 Special Design and Application. Hoods containing
    77. 513.8 Review and Certification. Where required, complete
    78. 513.9 Installation Requirements. Installation of systems
    79. 513.10 Portable Fire Extinguishers. Portable fire extinguisher…
    80. 513.11 Maintenance. Portable fire extinguishers shall be
    81. 513.12 Solid-Fuel Fire-Extinguishing Equipment.
    82. 514.1 Operating Procedures. Exhaust systems shall be
    83. 514.2 Inspection, Testing, and Maintenance. Maintenance of the…
    84. 514.3 Inspection for Grease Buildup. The entire exhaust
    85. 514.4 Cleaning of Exhaust Systems. If, upon inspection,
    86. 514.5 Cooking Equipment Maintenance. Inspection and
    87. 515.1 Cooking Equipment. Cooking equipment shall be
    88. 515.2 Operating Controls. Deep-fat fryers shall be equipped
    89. 516.1 General Requirements. Recirculating systems containing o…
    90. 516.2 Design Restrictions. All recirculating systems shall
    91. 516.3 Interlocks. The recirculating system shall be provided
    92. 516.4 Location and Application Restrictions. The
    93. 516.5 Additional Fire Safety Requirements. In addition to the …
    94. 516.6 Use and Maintenance. Automatic or manual covers on cooki…
    95. 517.1 Venting Application. Venting requirements of solidfuel c…
    96. 517.2 Location of Appliances. For cooking operations in
    97. 517.3 Hoods for Solid-Fuel Cooking. Hoods shall be sized
    98. 517.4 Exhaust Systems for Solid-Fuel Cooking. Where
    99. 517.5 Grease Removal Devices for Solid-Fuel Cook-
    100. 517.6 Air Movement for Solid-Fuel Cooking. Exhaust
    101. 517.7 Fire-Extinguishing Equipment for Solid-Fuel
    102. 517.8 Other Safety Requirements. Metal-fabricated solidfuel co…
    103. 518.1 General. Downdraft appliance ventilation system
    104. 518.2 Ventilation System. The downdraft appliance ventilation …
    105. 518.3 Fire-Extinguishing Equipment. For fire-extinguishing equ…
    106. 518.4 Airflow Switch or Transducer. An airflow switch or
    107. 518.5 Surface Materials. Any surface located directly
    108. 519.1 Where Required. Type II hoods shall be installed
    109. 519.2 Construction of Type II Hoods. Type II hoods
    110. 519.3 Type II Hood Exhaust System Net Airflow. The
    111. 519.4 Type II Exhaust Duct Systems. Ducts and
    112. 519.5 Termination of Type II Hood Exhaust System.
    113. 519.6 Makeup Air. Makeup air shall be provided in accordance w…
    114. 519.7 Independent Exhaust Duct System. Single or
  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 — GEOTHERMAL ENERGY SYSTEMS AND AMBIENT TEMPERATURE…
  18. Chapter 18 — REFERENCED STANDARDS
  19. Appendix A — RESIDENTIAL PLAN EXAMINER REVIEW FORM FOR HVAC SY…
  20. Appendix B — PROCEDURES TO BE FOLLOWED TO PLACE GAS EQUIPMENT …
  21. Appendix C — INSTALLATION AND TESTING OF OIL (LIQUID) FUEL-FIR…
  22. Appendix D — FUEL SUPPLY: MANUFACTURED/MOBILE HOME PARKS AND R…
  23. Appendix E — SUSTAINABLE PRACTICES
  24. Appendix F — SIZING OF VENTING SYSTEMS AND OUTDOOR COMBUSTION …
  25. Appendix G — EXAMPLE CALCULATION OF OUTDOOR AIR RATE
  26. Appendix H — PROFESSIONAL QUALIFICATIONS
  27. Appendix I — INDOOR HORTICULTURAL FACILITIES
  28. Appendix J — CLEAN AIR DELIVERY

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