Overpressure

Overpressure (or blast overpressure) is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion, and the resulting overpressure receives particular attention when measuring the effects of nuclear weapons or thermobaric bombs.

This article is about shock waves in the atmosphere. For other uses, see Overpressure (disambiguation).

Effects

According to an article in the journal Toxicological 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]

An EOD suit worn by bomb disposal experts can protect against the effects of BOP.[2][3]

Overpressure Effects
1 pound per square inch (6.9 kPa; 0.069 bar)
  • Window glass shatters
  • Light injuries from fragments occur
2 pounds per square inch (14 kPa; 0.14 bar)
  • Moderate damage to houses (windows and doors blown out and severe damage to roofs)
  • People injured by flying glass and debris
3 pounds per square inch (21 kPa; 0.21 bar)
  • Residential structures collapse
  • Serious injuries are common, fatalities may occur
5 pounds per square inch (34 kPa; 0.34 bar)
  • Most buildings collapse except concrete buildings
  • Injuries are universal, fatalities are widespread
10 pounds per square inch (69 kPa; 0.69 bar)
  • Reinforced concrete buildings severely damaged or demolished
  • Most people are killed
20 pounds per square inch (140 kPa; 1.4 bar)
  • Heavily built concrete buildings are severely damaged or demolished
  • Fatalities approach 100%

Calculation for an enclosed space

Overpressure in an enclosed space is determined using "Weibull's formula":[4][5]

where:

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

See also

References
  1. "Pulmonary Biochemical and Histological Alterations after Repeated Low-Level Blast Overpressure Exposures", Nabil M. Elsayed, and Nikolai V. Gorbunov, Toxicological Sciences, 2007 95(1):289-296 , online version 2006, http://toxsci.oxfordjournals.org/cgi/content/abstract/95/1/289
  2. Pavlus, John (March 4, 2010). "Real-life Hurt Locker: how bomb-proof suits work".
  3. "1) Effects of blast pressure on the human body" (PDF).
  4. Weibull, Hans R. W. (1968). "Pressures Recorded in Partially Closed Chambers at Explosion of TNT Charges". Annals of the New York Academy of Sciences. 152 (1): 357–361. Bibcode:1968NYASA.152..357W. doi:10.1111/j.1749-6632.1968.tb11987.x. S2CID 84258773.
  5. US patent 4474052, Bodurtha Jr., Frank T. & Bonifaz, Cristobal, "Laboratory barricade", issued October 2, 1984
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