What is the minimum clearance from the duct or exhaust fan to a combustible interior surface?

What is the minimum clearance from the duct or exhaust fan to a combustible interior surface?

• A. 12 inches
• B. 18 inches
• C. 24 inches
• D. 6 inches

Answer: (B)

Exhaust ducts and fans should be kept a safe distance from any combustible interior surfaces to prevent heat from transferring to those materials and to reduce the chance of ignition, especially where grease can accumulate. The standard minimum is 18 inches. This clearance creates a reliable safety buffer, giving heat and grease enough space to remain below ignition temperatures and allowing room for inspection and cleaning around the ductwork. If a surface isn’t combustible or if additional fire-rated protection is used, requirements can change, but for combustible interiors, 18 inches is the typical standard.

Exhaust ducts and fans should be kept a safe distance from any combustible interior surfaces to prevent heat from transferring to those materials and to reduce the chance of ignition, especially where grease can accumulate. The standard minimum is 18 inches. This clearance creates a reliable safety buffer, giving heat and grease enough space to remain below ignition temperatures and allowing room for inspection and cleaning around the ductwork. If a surface isn’t combustible or if additional fire-rated protection is used, requirements can change, but for combustible interiors, 18 inches is the typical standard.