Nonmetallic ducts must be constructed using which classification of duct material?

Nonmetallic ducts are required to be constructed from materials classified as either Class 0 or Class I due to their fire performance characteristics. Class 0 materials are those that have a limited flame spread and smoke generation, making them suitable for use in various building applications. Class I materials, while allowing for slightly higher flame spread, still meet stringent safety requirements, especially in terms of fire resistance.

These classifications ensure that the nonmetallic ducts can withstand potential fire hazards while minimizing the risk of smoke and toxic gas emissions. This is crucial for maintaining safety standards in buildings, as ducts often traverse various areas, including those that may not be regularly occupied. By adhering to these classification standards, builders and contractors help ensure the integrity of the mechanical systems during fire events, thereby aiming to protect occupants and property.

The other classifications do not apply to nonmetallic ducts due to their inherent properties or lack of compliance with fire safety standards. Therefore, using Class 0 or Class I materials for nonmetallic ducts ensures compliance with the code and promotes safety in building design and construction.