What is the maximum smoke-developed index for thermal and sound insulating materials when concealed in buildings of any type of construction?

The maximum smoke-developed index for thermal and sound insulating materials, when concealed in buildings of any type of construction, is set at 450. This index is part of the performance criteria established to assess the fire safety of building materials. A higher smoke-developed index indicates that a material produces more smoke when burned, which can significantly impact visibility and air quality during a fire.

This limit is important because, in the event of a fire, the ability of occupants to navigate to safety can be severely hindered by dense smoke. By keeping the smoke-developed index for these materials at 450 or less, building codes aim to provide a reasonable level of safety for building occupants, ensuring that even if a fire occurs, the smoke produced by concealed materials will not create an insurmountable barrier to escape.

In contrast, lower values for the smoke-developed index would impose stricter standards on insulating materials, which might not be practical for certain applications where thermal efficiency is necessary. Therefore, 450 serves as a balanced threshold that allows for effective insulation while considering fire safety requirements.