What type of explosion occurs when a smoldering fire receives a fresh supply of oxygen?

The type of explosion that occurs when a smoldering fire receives a fresh supply of oxygen is known as a back draft. This phenomenon happens when a fire has been burning in a limited oxygen environment, producing significant quantities of smoke and unburned fuel. When a new source of oxygen is suddenly introduced, such as when a door or window is opened, the smoldering materials can ignite explosively due to the increased availability of oxygen.

Back drafts are dangerous because they can cause sudden and intense fire behavior, potentially injuring people nearby and complicating firefighting efforts. Understanding back drafts is crucial for fire investigators, as they can provide insight into the conditions of a fire scene and help in determining the fire's origin and spread.

Other mentioned concepts like rollover and flashover pertain to different ignition and fire dynamics. Rollover refers to the flames igniting combustible gases or vapors that have accumulated in the upper layers of a space, while flashover is the rapid spread of flames throughout an entire room or area, occurring when all combustible materials reach their ignition temperature almost simultaneously. Diffused flames, on the other hand, describe a situation where flames are dispersed without a concentrated intensity, which does not relate to the explosion dynamic described in this scenario