Define flashover:

Define flashover:

• A. Superheated gasses ignite in the uppermost thermal layers and cause the fire to travel across the top of the compartment
• B. Superheated gasses have brought the entire contents of the container to their ignition temperature and the entire contents of the container ignite almost simultaneously
• C. The introduction of oxygen to an oxygen starved fire in a closed container, rapidly causing the four elements of the fire tetrahedron together, causing the room to violently burst into flame
• D. When a vessel holding liquid ruptures as a result of pressure being exerted on its sides when the liquid it holds boils and the resulting pressure exceeds the container's ability to hold it. When the vessel fails the ensuing release of vapor and liquid can be violent, causing explosive release of tremendous force

Answer: (B)

Flashover is the moment a developing room fire makes the jump to the entire space becoming involved. It happens when the heat in the compartment is high enough that all the fuels in the room reach their ignition temperatures and ignite almost simultaneously, so the whole contents flare up at once. That precise idea—the entire contents igniting nearly at the same time due to heat—is what this choice describes, and it’s why it’s the correct definition. The other scenarios refer to different phenomena: ignition of flames traveling along the ceiling layers, which is a ceiling-layer flash or rollover; a backdraft, which occurs when oxygen suddenly enters a closed, smoldering fire; and a vessel rupture that leads to an explosive release—none of which capture the rapid, total involvement character of flashover.

Flashover is the moment a developing room fire makes the jump to the entire space becoming involved. It happens when the heat in the compartment is high enough that all the fuels in the room reach their ignition temperatures and ignite almost simultaneously, so the whole contents flare up at once. That precise idea—the entire contents igniting nearly at the same time due to heat—is what this choice describes, and it’s why it’s the correct definition.

The other scenarios refer to different phenomena: ignition of flames traveling along the ceiling layers, which is a ceiling-layer flash or rollover; a backdraft, which occurs when oxygen suddenly enters a closed, smoldering fire; and a vessel rupture that leads to an explosive release—none of which capture the rapid, total involvement character of flashover.