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BRHS /
Pressure Effects from ExplosionsDirect Blast EffectsThese direct effects, also called primary effects, are caused by the dynamic pressure waves. Although the human body is able to adapt to slow pressure changes (diving, high altitudes, etc.) the dynamic changes in a blast front may cause severe damage. Those organs, where large differences in densities are encountered, like the lunge or the inner ear, are particularly vulnerable. Ear damage is not leading to death, but due to the ears’ high sensitivity it is often used as an indicator for an exposure. Lunge damage is depending on a combination of peak overpressure Ps and on the pulse duration tp (Fig. 1).  Fig. 2: Threshold data from Baker, NASA, and gaseous detonation data ([[http://hysafe.org/wiki/BRHS/PressureEffectsFromExplosions?action=bibentry&bibfile=DB&bibref=BakerWE:1983 | BakerWE:1983) (NASA:NSS:1740:16:1997) (DorofeevSB:1996a)]] Similar as for the structural effects threshold limits for ear and lunge damage are displayed in pressure-impulse diagrams (Fig. 2). However, as impulse and pressure are correlated, the coordinates pressure and pulse duration provide a clearer and decoupled view. The transformed data are given in Fig. 3. Not only for the general mixing and detonation initiation but also for the physiological effects the spatial confinement is a very important factor. Generally one has to expect an increased immediate and late mortality in closed space blast scenarios compared to open-air explosions (KlugerY:2003) (KaiserW:2002). However, usually only little mortality is due to these primary effects compared to the more severe combination of indirect blast effects, like missiles, body translation and associated impact and heat effects. Indirect Blast EffectsIndirect blast effects include secondary effects, these are generated by missiles (e.g. accelerated parts of the pressure vessel, parts of the building, glass, etc.) and tertiary effects linked to the body translation. Especially the impact, the deceleration when hitting a wall or any other a solid structure, can cause skull fractures with traumatic consequences, even death. With a simplified model the body displacement caused by the blast may be calculated and a lethality threshold may be attributed to the resulting velocities, see [Baker 1983]. See figures 1 and 2 with the skull fracture as the representative indirect blast effect. Invalid BibTex Entry! << Asphyxiation by Hydrogen | Content | Thermal Effects from Fires >> |
