What type of fuel is most likely to cause a backdraft?

The most likely type of fuel to cause a backdraft is solid wood products. When solid wood burns, it undergoes pyrolysis, which is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. As wood burns, it can produce a significant amount of combustible gases before it fully ignites.

In a confined space where there is limited oxygen, a fire may smolder on the surface of the wood while generating flammable gases. If the conditions are right—specifically, if a sufficient amount of these gases accumulate and then are suddenly exposed to a fresh air supply (like when a door is opened)—it can result in a backdraft. This is characterized by a rapid ignition of the combustibles, producing a robust and dangerous fire event.

Gasoline, flammable gases, and natural fibers can also be hazardous, but they have different combustion characteristics. Gasoline is highly volatile, leading to rapid ignition rather than a backdraft situation. Flammable gases can also ignite explosively but do not generally accumulate in the same way that smoke and gases from solid fuels can. Natural fibers might have similar properties to wood in certain respects, but their backdraft potential is lower compared to solid wood products due to their different burning characteristics.