Overpressure (orblast overpressure) is the pressure caused by ashock wave over and above normalatmospheric pressure. The shock wave may be caused bysonic boom or byexplosion, and the resulting overpressure receives particular attention when measuring theeffects of nuclear weapons orthermobaric bombs.

According to an article in the journalToxicological Sciences,

Blast overpressure (BOP), also known as high energy impulse noise, is a damaging outcome of explosive detonations and firing of weapons. Exposure to BOP shock waves alone results in injury predominantly to the hollow organ systems such as auditory, respiratory, and gastrointestinal systems.^[1]

AnEOD suit worn bybomb disposal experts can protect against the effects of BOP.^[2][3]

The above table details the effects of overpressure on the human body in a building affected by a blast of overpressure waves, as clarified later in the journal.

The human body can survive relatively high blast overpressure without experiencing barotrauma. A 5 psi blast overpressure will rupture eardrums in about 1% of subjects, and a 45 psi overpressure will cause eardrum rupture in about 99% of all subjects. The threshold for lung damage occurs at about 15 psi blast overpressure. A 35-45 psi overpressure may cause 1% fatalities, and 55 to 65 psi overpressure may cause 99% fatalities.^[3]

According to documents released by the United States MilitaryDefense Technical Information Center (DTIC),

Human beings have about a 50:50 chance of surviving 500 psi, but will probably be severely injured at 70-100 psi. Exposed eardrums will be ruptured 50% of the time at 15 psi. However, a standing man will be blown away at about 10 f/s velocity by a shock of 25 psi peak pressure.^[4]

It is important to note that this is for "Instantaneous peak pressure" while the preceding table is for long duration pressure.

Overpressure in an enclosed space is determined using "Weibull's formula":^[5][6]

${\displaystyle \mathrm{\Delta }p=22.5{\left(\frac{m}{V}\right)}^{0.72}\text{bars}}$

where:

• 22.5 is a constant based on experimentation
• ${\displaystyle m}$ = (kilograms)net explosive mass calculated using all explosive materials and their relative effectiveness
• ${\displaystyle V}$ = (cubic meters) volume of given area (primarily used to determine volume within an enclosed space)

• Bomb disposal

• Pressure
• Explosives
• Shock waves

• Articles with short description
• Short description matches Wikidata