Explosives and blast injuries

[Sommer]

In mass-casualty incidents involving explosions, three concentric zones are identified:

Blast epicenter
Secondary perimeter
Blast periphery

In a blast epicenter (kill zone), most people are dead or mortally injured. In the secondary perimeter (critical casualty zone), there are more survivors, but many of them likely have multiple injuries. In the blast periphery (walking-wounded zone), most casualties have non–life-threatening injuries and psychologic trauma.
An explosion creates a blast wave. An intense blast wave can tear tissue. A less intense blast can damage the eardrums, lungs, and abdomen. Blast waves also throw debris at very high speed that can injure any part of the body.

[Monty]

High-energy events in which a solid or liquid is converted rapidly to a gas can occur at 3 rates:

Deflagration: Rapid burning but minimal blast
Explosion: Subsonic ignition and blast wind (low-grade explosive)
Detonation: Supersonic ignition and blast wave (high-grade explosive)

An example of deflagration would be the rapid flash (without a bang) that results when an open pile of black powder (gunpowder) is ignited. The same black powder confined tightly in a container would cause a low-grade explosion. In high-grade explosives, the ignition wave travels through the material at supersonic speed and causes a supersonic blast (detonation) wave; common examples include nitroglycerin and trinitrotoluene (TNT—Examples of Low-Grade and High-Grade Explosives).
In mass casualty incidents involving explosions, 3 concentric zones are identified:

Blast epicenter
Secondary perimeter
Blast periphery

In the blast epicenter (kill zone), any survivors are probably mortally injured, technical rescue capabilities and extrication are likely to be required, and advanced life support and high victim-to-care-provider ratios are required for any survivors. In the secondary perimeter (critical casualty zone), survivors will have multiple injuries, and standard rescue capabilities and moderate victim-to-care-provider ratios are required. In the blast periphery (walking-wounded zone), most casualties will have non–life-threatening injuries and psychologic trauma, no rescue is required, and basic support and self-help are needed.
(See also Overview of Incidents Involving Mass-Casualty Weapons.)