Description/EtiologyBlasts, or explosions, cause devastating injuries by a variety of mechanisms. At detonation, a blast produces an outward, high-pressure shock wave that travels radially at supersonic speed from the center of the blast, with a leading edge that immediately increases air pressure. This is followed by a powerful reverse wind, pulling back in the direction of the blast, leading to underpressurization. The shock wave causes progressively less damage as it moves away from the origin of the blast. Generally, all persons in the immediate vicinity (e.g., within 5 feet [1.5 m]) of a blast that is 200–250 psi (13.6–17.0 atmospheres) will be killed. Blasts cause more injuries if they occur in confined spaces (e.g., in buildings, mines, large vehicles) or if the shock wave moves through narrow streets.Over 100,000 military service members suffer from traumatic brain injuries caused by explosive devices, which is a result of being exposed to blast overpressure from firing large-caliber weapons (e.g., Carl Gustaf recoilless rifle). Service members exposed to these explosives or high-caliber weapons (even during training) can develop various cognitive deficits, especially those involving memory loss. A crucial mechanism for brain injuries are primary blast pressure waves caused when firing these large-caliber weapons. Currently, the United States Army does not provide protection against blast injuries caused by explosives.