What is the minimum clearance required for a grease duct serving a Type I hood to combustible construction?

The minimum clearance required for a grease duct serving a Type I hood to combustible construction is 18 inches. This clearance is crucial in providing a safe distance to prevent heat transfer and potential ignition of combustible materials.

The need for this clearance is primarily due to the high temperatures and the possibility of grease accumulation within the ductwork. The 18-inch clearance helps ensure that any heat generated or accumulated in the duct does not reach combustible surfaces, thereby reducing the risk of fire hazards.

Maintaining proper clearance also aligns with various safety codes and standards designed to enhance fire safety in commercial kitchen environments, where grease-laden vapors are common. This is essential to comply with the North Carolina Mechanical Code and to promote the overall safety and efficiency of the kitchen's ventilation system.