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Earlier editions: 20222019

Chapter 5 — EXHAUST SYSTEMS

510.9 Termination of Type I Hood Exhaust System.

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.

The exhaust system shall terminate as follows:

(1) Outside the building with a fan or duct.

(2) Through the roof or to the roof from outside, as in Section 510.9.1, or through a wall, as in Section 510.9.2. [NFPA 96:7.8.1] 510.9.1 Rooftop Terminations. Rooftop terminations shall be arranged with or provided with the following:

(1) A minimum of 10 feet (3048 mm) of horizontal clearance from the outlet to adjacent buildings, property lines, and air intakes.

(2) A minimum of 5 feet (1524 mm) of horizontal clearance from the outlet (fan housing) to any combustible structure.

(3) A vertical separation of 3 feet (914 mm) above any air intakes within 10 feet (3048 mm) of the exhaust outlet.

(4) The ability to drain grease out of any traps or low points formed in the fan or duct near the termination of the system into a collection container that is noncombustible, closed, rainproof, and structurally sound for the service to which it is applied and that will not sustain combustion.

(5) A grease collection device that is applied to exhaust systems that does not inhibit the performance of any fan.

(6) Grease collection systems that meet the requirements of Section 510.9.1(4) and Section 510.9.1(5).

(7) A listed grease duct complying with Section 507.4.7 or ductwork complying with Section 507.4.8.

(8) A hinged upblast fan supplied with flexible weatherproof electrical cable and service hold-open retainer to permit inspection and cleaning that is listed for commercial cooking equipment with the following conditions:

(a) Where the fan attaches to the ductwork, the ductwork is a minimum of 18 inches (457 mm) away from any roof surface, as shown in Figure 510.9.1.

(b) The fan discharges a minimum of 40 inches (1016 mm) away from any roof surface, as shown in Figure 510.9.1.

(9) Other approved fan, provided it meets all of the following criteria:

(a) The fan meets the requirements of Section 510.9.1(3) and Section 511.1.3.

(b) Its discharge or its extended duct discharge meets the requirements of Section 510.9.1(2). (See Section 511.1.3)

(c) Exhaust fan discharge is directed up and away from the roof surface. {NFPA 96:7.8.2.1}

For SI units: 1 inch = 25.4 mm, 1 foot = 304.8 mm

FIGURE 510.9.1

UPBLAST FAN CLEARANCES

[NFPA 96: FIGURE 7.8.2.1]

510.9.1.1 Listed Vibration Isolation Connec-

tors. Listed vibration isolation connectors shall be permitted to be used on exterior roof locations where required for proper equipment vibration isolation. 510.9.1.2 Inspection and Cleaning. Fans shall be provided with safe access and a work surface for inspection and cleaning. [NFPA 96:7.8.2.2]

510.9.2 Wall Terminations. Wall terminations shall be arranged with or provided with the following properties: (1) The termination shall be through a noncombustible wall with a minimum of 10 feet (3048 mm) of clearance from the outlet to adjacent buildings, property lines, grade level, combustible construction, electrical equipment or lines, and with the closest point of any air intake or operable door or window at or below the plane of the exhaust termination. The closest point of any air intake or operable door or window above the plane of the exhaust termination shall be a minimum of 10 feet (3048 mm) in distance, plus 3 inches (76 mm) for each 1 degree (0.017 rad) from horizontal, the angle of degree being measured from the center of the exhaust termination to the center of the air intake or operable door or window, as indicated in Figure 510.9.2. Exception: A wall termination in a secured area shall be permitted to be at a lower height above grade if acceptable to the Authority Having Jurisdiction. (2) The exhaust flow shall be directed perpendicularly outward from the wall face or upward. (3) All the ductwork shall be pitched to drain the grease back into the hood(s) or with a drain provided to bring the grease back into a container within the building or into a remote grease trap. (4) A listed grease duct shall comply with Section 510.3.3 through Section 510.3.7; other ducts shall comply with Section 510.5.

EXHAUST SYSTEMS

(5) An approved fan shall meet the requirements of Section 510.9.2(3), and Section 511.1.1 or Section 511.1.3. [NFPA 96:7.8.3]

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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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