Repost - A backdraft occurs when a fire in a confined space, like a house, consumes most of the available oxygen and slows down, producing a lot of unburned gases. Imagine a room filled with smoke and hot gases that are just waiting for oxygen. When a door or window is opened, fresh oxygen rushes in and rapidly ignites these gases, causing an explosive burst of flames and pressure. Think of it like a balloon filled with air. If you suddenly let go of the balloon's opening, the air rushes out for