Explain flashover and what triggers it.

• A. Flashover is the rapid ignition of all fuels in a compartment due to heat buildup; triggered by reaching a critical heat level and sustained heat transfer leading to autoignition of fuels.
• B. Flashover is the extinguishment of a fire.
• C. Flashover is the ignition of a single fuel source due to oxygen.
• D. Flashover is the cooling of surfaces by water.

Answer: (C)

Flashover tests your understanding of how a fire in a confined space can suddenly shift from flames in one area to the entire compartment being involved. It happens when heat from the growing fire builds up inside the room and causes all exposed fuels to reach their ignition temperatures. The trigger is reaching a critical heat level with sustained heat transfer that drives the ignition of fuels — often multiple ones at once — due to heat feedback, not because of lighting a single fuel by oxygen alone. Oxygen is needed for combustion, but it’s the intense heat and the accumulation of flammable gases from pyrolysis that pushes the whole room into flame. So flashover is a rapid, nearly simultaneous ignition of many fuels in the space, not the extinguishment, not cooling, and not the ignition of just one fuel.