Grease duct cleanouts and openings shall comply with all of the following:
- Grease ducts shall not have openings except where required for the operation and maintenance of the system.
- Sections of grease ducts that are inaccessible from the hood or discharge openings shall be provided with cleanout openings spaced not more than 20 feet (6096 mm) apart and not more than 10 feet (3048 mm) from changes in direction greater than 45 degrees (0.79 rad).
- Cleanouts and openings shall be equipped with tight-fitting doors constructed of steel having a thickness not less than that required for the duct.
- Cleanout doors shall be installed liquid tight.
- Door assemblies including any frames and gaskets shall be approved for the application and shall not have fasteners that penetrate the duct.
- Gasket and sealing materials shall be rated for not less than 1500°F (816°C).
- Listed door assemblies shall be installed in accordance with the manufacturer's instructions.
Where ductwork is large enough to allow entry of personnel, not less than one approved or listed opening having dimensions not less than 22 inches by 20 inches (559 mm by 508 mm) shall be provided in the horizontal sections, and in the top of vertical risers. Where such entry is provided, the duct and its supports shall be capable of supporting the additional load, and the cleanouts specified in Section 506.3.8 are not required.