what is a backdraft

A backdraft is a sudden and explosive burning of superheated gases in a fire caused by the rapid introduction of oxygen into a hot, oxygen-depleted environment, such as when a window or door to an enclosed space is opened or broken. Backdrafts are typically seen as a blast of smoke and/or flame out of an opening of a building and present a serious threat to firefighters. Backdrafts are different from flashovers, which are thermally driven, as backdrafts are air-driven events. Signs of backdraft conditions include black smoke becoming dense, greyish yellow without visible flames, a well-sealed building indicating air confinement and excessive heat buildup, and a developing fire that may consume the available oxygen before its able to flashover or may rapidly decline due to insufficient oxygen and the increasing volume of combustion products. Firefighters can defuse a potential backdraft by ventilating a room from its highest point, allowing the heat and smoke to escape without igniting.