Ducts for domestic kitchen cooking appliances with downdraft exhaust systems can be constructed of which material?

In the context of duct systems for domestic kitchen cooking appliances with downdraft exhaust systems, it is important to consider the appropriate material that meets safety and performance standards. The correct type of ducting for downdraft systems must be capable of withstanding heat and must not emit harmful gases when exposed to high temperatures.

The use of Schedule 40 PVC pipe is not suitable because it is designed for low-temperature applications typically seen in plumbing, such as drain, waste, and vent applications. PVC can warp or degrade when exposed to the heat generated by cooking appliances, thus posing a safety risk during operation.

In contrast, metal ducting is often recommended for kitchen venting because it can handle the heat generated by cooking appliances and does not pose the risk of melting or off-gassing like plastic materials.

The other choices, flexible plastic ducting and Schedule 40 aluminum, also have limitations that make them less suitable for downdraft exhaust needs. Flexible ducting can restrict airflow and create pressure drops due to its design, while Schedule 40 aluminum may not meet the required strength and durability under high temperatures.

Thus, the most appropriate material for ducting in this application, based on meeting safety and efficiency standards, is indeed metal ducting, which is