What type of grease duct system is required for Type I hoods?

Type I hoods, which are designed for the capture of grease-laden vapors from cooking operations, require specific duct systems to ensure safe and efficient exhaust. The correct choice of a double-wall duct system is crucial due to the need for both structural integrity and fire safety.

Double-wall duct systems create an insulating layer between the inner and outer walls, which helps in maintaining the temperature of the exhaust air and preventing overheating of the outer duct surface. This is particularly important for grease ducts, as the combustibility of grease can pose a significant fire hazard if the temperatures are not adequately managed. Moreover, the insulation provided by a double-wall system reduces the amount of heat transferred to nearby combustible materials, thereby minimizing the risk of ignition.

In contrast, single-wall duct systems lack this insulation and may not adequately contain the heat from the exhaust, leading to potential fire risks. Insulated systems, while they do reduce heat transfer, might not meet the structural and safety requirements necessary for handling high-velocity, grease-laden air.

Therefore, the double-wall duct system is specifically designed to handle the demands of Type I hoods, ensuring compliance with safety standards and reducing risks associated with cooking exhaust.