When do smoke explosions typically occur after the opening of a door or window?

Smoke explosions, often referred to as backdrafts or flashovers, typically occur within 2-3 seconds after the opening of a door or window. This timing is critical because it corresponds to the moment when fresh oxygen is introduced to an environment that is already filled with smoke and heat. When the door or window is opened, oxygen can ignite the accumulated flammable gases that have built up in the compartment, leading to an explosive combustion reaction.

This specific window of 2-3 seconds is significant, as it reflects the rapid changes in the fire dynamics occurring in a confined space. If sufficient heat and flammable gases are present, the introduction of oxygen can lead to a sudden ignition, causing a smoke explosion. Awareness of this timing is vital for firefighters when they are entering a structure, as it helps them assess the potential dangers and make strategic decisions to ensure their safety and effectiveness in firefighting operations.