What does the term exposed surface refer to?

The term "exposed surface" specifically refers to the side of a structure that is directly exposed to fire. This area becomes critical during fire investigations as it can provide essential evidence regarding the fire's heat exposure, duration, and intensity. Investigators analyze these surfaces to determine the effects of heat on materials, which can help ascertain fire spread patterns and the origin of the fire.

Understanding the characteristics of exposed surfaces can lead to conclusions about how the fire behaved upon encountering different materials and might even highlight areas that experienced significant damage, allowing for a more thorough understanding of the incident. Thus, the concept of exposed surfaces is integral to fire dynamics and the subsequent investigation process as outlined in NFPA 921.