Nonmetallic ducts must be constructed with which class of duct material?

Nonmetallic ducts must be constructed using materials classified as Class 0 or Class I. This classification indicates that the material meets specific flame spread and smoke development ratings that are crucial for safety in building design. Class 0 materials have the highest level of fire safety, representing the least amount of flame spread, while Class I materials are also designed to resist fire but may allow for slightly more flame spread compared to Class 0.

This requirement is significant in mechanical code to ensure that the ductwork does not contribute to the spread of fire and to minimize smoke production, which could pose a risk during emergencies. The compliance with these classes of materials helps in maintaining safety standards and mitigating potential hazards in HVAC systems, especially in situations where ducts may be exposed to fire or heat.