What is the minimum required opening dimension for cleanouts serving horizontal sections of grease ducts?

The minimum required opening dimension for cleanouts serving horizontal sections of grease ducts is established to ensure proper access for maintenance and cleaning. This is particularly important in grease ducts, as they can accumulate grease buildup that, if not addressed, poses fire hazards and reduces overall duct efficiency.

The 12 inches x 12 inches dimension allows sufficient space for technicians to effectively clean the ductwork, inspect for any potential blockages, and maintain the system. Adequate access is crucial in ensuring the grease duct operates efficiently while minimizing safety risks.

The other dimensions provided in the options represent larger openings which may not be necessary for the routine maintenance of grease ducts. While having larger cleanouts may be beneficial in some contexts, the established code specifies 12 inches x 12 inches as the minimum required size to ensure safety and maintainability in these systems.