During this phase of fire, the oxygen level drops and there is extreme heat with high gas and smoke production, around 1200 F+, which phase is described?

• A. Free Burning
• B. Flashover
• C. Smoldering
• D. Puffback

Answer: (A)

Flashover is the phase described. In flashover, the fire consumes the available oxygen rapidly and the temperature soars—temperatures around 1200 F (about 650 C) are typical. This intense heat pushes the fire toward a transition where virtually every combustible in the room ignites almost at once, turning a localized flame into a fully involved room-and-contents fire with heavy gas and smoke production. That rapid rise in temperature and shift to full involvement is why oxygen levels drop and heat becomes extreme.

The other scenarios don’t fit as well: free burning involves flames with oxygen readily available and not the same rapid rise in temperature; smoldering is characterized by slow, low-heat combustion with little visible flame; puffback is a sudden ignition event caused by re-entrance of air into a fuel-rich space, not the rapid, room-wide involvement associated with flashover.