Does charring on vertical surfaces of walls, closed doors, and objects face toward the area or point of origin?

• A. No
• B. Sometimes
• C. Not enough information
• D. Yes

Answer: (D)

Charring happens on the surface that is directly exposed to the heat source. When flames or intense radiant heat strike a wall, door, or object, the material on that exposed face undergoes pyrolysis and forms a char layer. This char develops on the side toward the fire (the area of origin) and tells you which side is being heated. As a result, you would expect to see charring on vertical surfaces, closed doors, and objects on the side facing the fire. This directional charring also helps slow heat transfer, since the char layer acts as insulation, but the initial char formation occurs on the fire-facing surface.