Firefighters nightmare: backdraft explosion

A backdraft explosion from The Gray Monk

Today's CNN news reports on a backdraft explosion at a fire in Ohio. This type of explosion can occur when an oxygen-starved fire suddenly gains access to oxygen, for example when a window breaks or a door is opened. It is a dangerous and well-known phenomenon for firefighters.  An oxygen starved fire produces combustible gases, primarily carbon monoxide, and smoke.  When these gain access to oxygen, combustion can take off again raising the temperature of the gases. Because they heat up, they expand, often extremely rapidly.

As the smoldering fire sucks in oxygen, there is often a "puffing" effect as the fire gets a little, but not enough, oxygen.  As the fire puffs, smoke produced by the fire is often sucked back into the burning area, giving rise to the term "backdraft." Firefighters are taught to avoid these dangerous situations, and to attempt to deal with it by ventilating the fire from the highest point. This allows the heat and smoke produced when the combustion reignites to escape through the highest point without exploding.

Wiki is full of all sorts of interesting trivia! There was a 1991 film "Backdraft" in which a serial arsonist was using backdrafts as a means for assassinating people! Also, if your house burns down and you've got papers stored in a safe--don't rush in to open it!! After the 1906 San Francisco earthquake and fire, business people who opened warm safes to recover their unburned papers exposed the hot gas of the interiors to an oxygen source, immediately and explosively setting the papers on fire!