Ducts must be constructed or supported by which material to meet standards?

Ducts in commercial cooking operations are required to be constructed or supported by carbon steel or stainless steel to meet the standards outlined in NFPA 96. This requirement is critical because these materials offer superior durability and heat resistance, which are essential in environments where high temperatures and the presence of grease are prevalent. Steel's properties allow it to withstand the thermal expansion and contraction that occur during cooking operations.

Additionally, stainless steel is particularly valued for its corrosion resistance, making it ideal for the greasy and humid environments typically found in kitchens. The use of these materials helps minimize the risk of fire hazards, as they can better contain and resist the ignition of grease-laden vapors.

Other materials such as plastic or PVC, wood, aluminum, and fiberglass do not meet the stringent fire safety performance requirements necessary for commercial kitchen ductwork. These materials may not possess the necessary heat resistance or structural integrity, making them unsuitable and potentially hazardous for use in a commercial cooking environment.