What is the minimum distance a grease duct must have from combustible construction?

The minimum distance a grease duct must maintain from combustible construction is 18 inches. This requirement is in place to reduce the risk of fire hazards that can arise due to the high temperatures associated with grease duct systems. By establishing an 18-inch clearance, the code aims to prevent any potential ignition of surrounding combustible materials that could be exposed to heat generated by the duct system or from any grease buildup that may catch fire.

This distance is part of broader safety measures included in the mechanical code to ensure that installations are carried out in a manner that minimizes the chances of fire spread and protects the integrity of the building and the safety of its occupants.