What is a key requirement for materials used in sealing clothes dryer exhaust ducts?

The key requirement for materials used in sealing clothes dryer exhaust ducts is that they must be noncombustible. This is crucial because dryer exhaust systems can reach high temperatures and may carry lint, which is a combustible material. If the duct materials are combustible, there is a significant risk of fire developing, especially if the dryer malfunctions or if the ducts are not cleaned regularly.

Noncombustible materials help to ensure that any heat generated in the dryer exhaust system does not ignite the ductwork or any surrounding materials. This requirement is a fundamental safety measure designed to minimize fire hazards and protect both the property and the occupants in the building. Moreover, codes and standards emphasize the importance of using materials that withstand fire hazards, further supporting the necessity for noncombustible materials in this application.