# Blast Overpressure?



## Summit (Aug 23, 2007)

What are the blast overpressure threshholds for various injuries (eg blast lung, tympanic rupture, GI contusions/ruptures) due to blast overpressure from conventional explosives? Do the threshhold values tend to change with ambient pressure or if the victim+detonation occur in water?


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## ffemt8978 (Aug 23, 2007)

Don't know if this helps or not, but it may point you in the right direction.

http://www.emedicine.com/emerg/topic63.htm


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## Shabo (Aug 24, 2007)

*Blast overpressure*

Summit,
Here is a link to a free on line course in the medical effects of primary blast injuries. The course covers: types of explosives, factors for pressure phase damage, overpressure limits, effects of confined vs open air blast, etc. we actually had to take this as part of my EMT-Basic course. As for water blast, It's not covered in this course. 

Shabo

http://www.teexwmdcampus.com/


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## VentMedic (Aug 25, 2007)

Good general article covering ground and water. 

http://mediccom.org/public/tadmat/training/NDMS/Blast_Document.pdf




> An underwater blast wave has particular lethality because water is incompressible compared with air. Therefore, a wave resulting from a blast occurring underwater travels farther and faster than a wave from a similar explosion on land. Hence, blast injuries in water occur at greater distances from the detonation point and are often more severe.






> Primary blast injury has three primary mechanisms. The first is spalling, which occurs when the shock wave (blast wave) transfers from a dense medium (liquid) such as water to a less dense medium (gas) such as air. In an underwater explosion, for example, the shock wave travels in front of the detonation, reaches the surface, and reflects off the less dense air. This scenario is comparable to the effect of striking the outside of a rusty bucket with a hammer. The transfer of energy displaces rust from the inside of the bucket, even though the hammer did not strike it directly.



*Selected Pressure Effects of Explosions* *
*Pressure (pounds per square inch) Effect *
5       Possible tympanic membrane rupture 
15     50% incidence of tympanic membrane rupture 
30     Possible lung injury 
40     Concrete shatters 
75     50% incidence of lung injury 
100    Possible fatal injuries 
200    Death more likely than not 
*Adapted from Kizer KW. Dysbarism. In Tintinalli JE, Kelen GD, Stapyczynski JS (eds). 
Emergency Medicine: A Comprehensive Study Guide, 5th edition. New York, McGraw-
Hill, 2000, p 1276.


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## sandboxmedic (Aug 26, 2007)

VentMedic said:


> Good general article covering ground and water.
> 
> http://mediccom.org/public/tadmat/training/NDMS/Blast_Document.pdf
> 
> ...


Good Post, i havnt seen it broken down that well before. Thanks Ventmedic


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## DisasterMedTech (Oct 8, 2007)

*Hmmm...*

Being relatively new to Disaster Medicine, I hadnt really thought of over blast very much yet. I think disaster response teams, say to Ground Zero, tend to think the danger of further disaster is over once our boots on the ground. This was a good reminder for me. Thanks for posting the link. I will definitely be taking the course linked in this thread.


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