What term is used to describe an explosion that occurs when unburned gas ignites rapidly with introduced oxygen?

The correct term for an explosion that occurs when unburned gas ignites rapidly with the introduction of oxygen is known as a backdraft. This phenomenon typically occurs in confined spaces where a fire has burned up most of the available oxygen, allowing flammable gases to accumulate without being ignited. When oxygen is suddenly introduced—such as through an opening like a door or window—the concentrated flammable gas can ignite explosively due to the rapid mixing of oxygen with these combustible gases.

Understanding this concept is crucial for firefighters, as recognizing the signs of a potential backdraft can help them avoid dangerous situations. By being aware of the conditions that lead to a backdraft, firefighters can make informed decisions about ventilation and other tactics during fire suppression operations.