occurs at the stage of a fire at which all surfaces and objects
within a space have been heated to their ignition temperature,
and flame breaks out almost at once over the surface of all objects
in the space. Thetemperature is between 932 to 1,112 degrees Fahrenheit,
although flashover temperatures can peak at about 2,000 degrees
The first phase of flashover results from the ignition of flammable
gases produced by combustion (primarily carbon monoxide) that
have accumulated in the upper parts of the fire area. As this
is happening, the radiant heat of the original fire is heating
nearby combustibles--the walls, furniture, anything in the room--and
these also begin giving off flammable gases. This is called "pyrolysis."
In this phase, smoke banks down quickly, reducing visibility dramatically.
phase of flashover is the rollover or flaming of these gases near
the ceiling. This may appear as small flashes of flame in the
dense smoke, or as rollover, a flame front rolling out across
the ceiling. The fire has now changed from a steady-state fire
to an aggressive, fast moving fire.
fire development is complete as conditions move into final phase:
thermal collapse. Intense radiant heat pours down from all around.
You can no longer get under the thermal balance (the stratified
layer of heat and smoke). Like a building collapse, intense heat
drops to floor level.
were ok after this flashover. There is still one at top of ladder
and one on the ladder! The Firefighter on the ground was knocked
off the ladder.
This picture is courtesy of Aaron Burns of Local 2551.