What is the maximum allowable flame-spread index for wall and ceiling finishes?

The maximum allowable flame-spread index for wall and ceiling finishes is established to ensure safety in buildings by limiting the potential for fire to spread rapidly. A flame-spread index of 200 is the threshold for Class B materials according to the standards set by the relevant building codes and safety guidelines. This means materials falling within this category are more resistant to flaming combustion, thereby enhancing safety for occupants in the event of a fire.

Materials with a flame-spread index of above 200 do not meet the minimum safety standards for most building applications, where fire safety is a critical concern. Consequently, materials must undergo testing to determine their flame-spread characteristics to ensure they comply with the stipulated limits. The Class B rating (flame-spread index of 0 to 200) helps to mitigate the risks associated with fire, thus making it essential for materials used in wall and ceiling finishes to adhere to this criterion.