Flashover, Rollover, Backdraft and Smoke Explosion

Smoke from a fire may contain combustible material released by pyrolysis. If this material ignites then a "flashover" may occur.

Amount of Combustible Material	Oxygen	Ignition Source	Confinement of Smoke	Type of Flashover
low to moderate	present	generating source	closed	lean
high	none	generating source	closed	rich
high	present	autoignition	open	hot rich
high	present	any	open	delayed

where:

• A confined space can result in overpressures.

Type of Flashover	Alternative Term
lean	rollover
rich	backdraft
hot rich	autoignition, self-ignition
delayed	smoke explosion; smoke gas explosion

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