What fire behavior term describes ignition of accumulated fuel gases near the ceiling as the heat front reaches them?

What fire behavior term describes ignition of accumulated fuel gases near the ceiling as the heat front reaches them?

• A. Backdraft
• B. Flashover
• C. Roll-over (ceiling gas ignition indicating impending flashover)
• D. Puffback

Answer: (C)

It describes the ignition of accumulated fuel gases near the ceiling as the heat front reaches them. As a fire grows, hot combustion products and vapors roll up and pool at the ceiling, creating a flammable layer. When the heat front arrives at this ceiling gas layer and there’s enough oxygen, the gases ignite, creating a rolling flame along the ceiling. This ceiling gas ignition is a classic sign that flashover is looming—the fire has heated the space to the point where the entire room can rapidly ignite. This differs from backdraft, which happens when a closed area containing hot, fuel-rich air is suddenly opened to air and an explosive ignition occurs; flashover is the full-room ignition of all fuels as heat rises to a critical level; puffback is a separate, usually less dramatic ignition event often related to residual fuel in lines or appliances, not the ceiling gas layer ignition described here.

It describes the ignition of accumulated fuel gases near the ceiling as the heat front reaches them. As a fire grows, hot combustion products and vapors roll up and pool at the ceiling, creating a flammable layer. When the heat front arrives at this ceiling gas layer and there’s enough oxygen, the gases ignite, creating a rolling flame along the ceiling. This ceiling gas ignition is a classic sign that flashover is looming—the fire has heated the space to the point where the entire room can rapidly ignite.

This differs from backdraft, which happens when a closed area containing hot, fuel-rich air is suddenly opened to air and an explosive ignition occurs; flashover is the full-room ignition of all fuels as heat rises to a critical level; puffback is a separate, usually less dramatic ignition event often related to residual fuel in lines or appliances, not the ceiling gas layer ignition described here.