What minimum class rating is acceptable for interior finishes in atrium spaces according to safety regulations?

In atrium spaces, the minimum class rating for interior finishes that is considered acceptable according to safety regulations is Class B. Class B materials offer a moderate level of flame spread resistance, which is critical in areas like atriums where smoke and heat can travel quickly and potentially endanger occupants. These areas often feature high ceilings and large open spaces that require materials that not only meet aesthetic and functional requirements but also ensure safety in terms of fire performance.

The designation of Class B indicates that the materials have a flame spread index greater than that of Class C but less than that of Class A. Class A materials are generally preferred for their superior fire performance, but the requirement for Class B in atrium spaces balances safety with practical considerations, such as cost and availability, while still providing an adequate level of fire resistance for such large, open environments. This guideline helps ensure that occupants can evacuate safely in case of a fire, and it aligns with overall building code requirements pertaining to fire safety.