What does a deeper char on a material indicate?

A deeper char on a material indicates a longer exposure to fire. When a material experiences prolonged heat and flame, it undergoes pyrolysis, resulting in the breakdown of its structure and the formation of char. This process effectively removes volatiles and changes the material's properties, making it more carbon-rich and less capable of supporting combustion.

The presence of deeper char suggests that the material has sustained significant thermal damage and was subjected to high temperatures for an extended duration. This information is critical for firefighters as it provides insights into the intensity and duration of the fire, which can influence tactical decisions during firefighting operations and the evaluation of structural integrity after the incident.