What is the flame spread rating limit for insulation applied to ducts in buildings other than dwellings or apartments?

The flame spread rating limit for insulation applied to ducts in buildings other than dwellings or apartments is 25. This rating is established by various building codes and standards, including the National Fire Protection Association (NFPA) and the International Building Code (IBC).

A flame spread rating indicates how quickly flames will spread across the surface of a material. The lower the rating, the better the material resists flame spread. For ducts in commercial or industrial applications, a flame spread rating of 25 is used to ensure that the insulation does not pose a significant fire hazard, thus contributing to overall safety in larger, more complex building environments.

Materials with a flame spread rating of 25 or less are considered acceptable for this application, helping to facilitate safe ventilation systems while minimizing fire risks. In residential settings, the standards may differ, reflecting the unique safety requirements and risks associated with different types of buildings.