The Slow Mo Guys film one scariest occurrences in a firefighter’s occupation in 4K slow motion.
A backdraft is a dramatic event caused through rapid re-introduction of oxygen to combustion into an oxygen-depleted environment in a fire; for example, the breaking of a window or opening of a door to an enclosed space.

A backdraft can occur when a compartment fire has little or no ventilation, leading to slowing of gas-phase combustion (due to the lack of oxygen); however, the combustible fuel gases (unburnt fuel vapor and gas-phase combustion intermediates such as hydrocarbons and carbon monoxide) and smoke (primarily particulate matter) remain at a temperature hotter than the auto-ignition temperature of the fuel mixture. If oxygen is then re-introduced to the compartment, e.g. by opening a door or window to a closed room, combustion will restart, often rapidly, as the gases are heated by the combustion and expand rapidly because of the rapidly increasing temperature.