What is a BLEVE and why is it dangerous in railroad accidents involving flammable chemicals?

A BLEVE, which stands for Boiling Liquid Expanding Vapor Explosion, occurs when a pressurized vessel containing a liquid that is heated above its boiling point fails. In such cases, the liquid is normally kept in a state that prevents it from boiling due to pressure; when that vessel is breached, the drop in pressure allows the liquid to rapidly vaporize and expand. This rapid expansion can lead to a violent explosion as the vapor escapes and ignites if flammable materials are present.

In railroad accidents involving flammable chemicals, a BLEVE is particularly dangerous because the sudden release of vapor can result in a large fireball or explosion capable of causing significant destruction and injury in the surrounding area. The energy released during a BLEVE can create a shockwave, and the intense heat from the fire can ignite other surrounding materials.

Understanding this process highlights the importance of safety protocols when transporting and handling pressurized hazardous materials. Each of the other answers does not accurately describe the mechanism or the unique danger presented by a BLEVE.