Backdrafts are extremely dangerous events that can occur during structure fires. They happen when a fire in an enclosed space consumes most of the available oxygen, causing combustion to slow while heat and flammable gases continue to build. If oxygen is suddenly reintroduced, such as when a door or window is ventilated these gases can ignite explosively, resulting in a violent blast. This can cause significant structural damage and serious injury or death to firefighters and others nearby. To prevent backdrafts, firefighters must assess conditions carefully before ventilation, look for signs like smoke puffing from openings, blackened windows, or no visible flame, and use controlled ventilation tactics to release heat and gases safely.