What type of explosion is characterized by a rapid phase change and vapor expansion?

The correct answer is the boiling liquid expanding vapor explosion, commonly referred to as BLEVE. This type of explosion occurs when a vessel containing a pressurized liquid, typically a flammable liquid or gas, experiences a failure at high temperature or pressure. When the vessel ruptures, the liquid rapidly vaporizes due to the sudden drop in pressure, leading to an explosive expansion of vapor.

BLEVE is particularly dangerous because it combines the hazards of both the pressure of the boiling liquid and the potential ignition of vapor, resulting in a violent explosion and a fireball if the vapor ignites. The key characteristic of BLEVE is this rapid phase change from liquid to gas and the explosive expansion that follows, which distinguishes it from other types of explosions.

In contrast, a fireball explosion involves the ignition of combustible vapor but does not necessarily involve the rapid phase change associated with a BLEVE. Deflagration is a slower combustion process, characterized by subsonic combustion waves, which differs significantly from the rapid expansion seen in BLEVE. Shock waves are produced by high-energy explosions but do not describe the specific phase change dynamics associated with BLEVE.