What is the maximum flame spread index allowable for thermal and sound insulating materials when concealed in buildings of any type of construction?

The maximum allowable flame spread index for thermal and sound insulating materials when concealed in buildings of any type of construction is set at 25. This standard is based on fire safety regulations aimed at limiting the spread of fire within concealed spaces. The flame spread index is a measure of how quickly flames will spread across the surface of a material. A value of 25 indicates that the material is considered to be of limited combustibility, providing a greater level of safety by controlling and slowing the rate at which flames can travel if a fire occurs. This is particularly important in commercial buildings where the safety of occupants and the protection of property are critical. Using materials with a flame spread index of 25 or lower helps in ensuring compliance with building codes and enhances the overall fire safety of the structure.