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If a person suffers exposure to a high explosive or low explosive blast, how much of their injuries will be due to the sudden decompression immediately after the shockwave?

Sudden decompression can have impressive looking, explosive effects, and I've heard that the rapid decompression from blasts is about as bad as being hit by the shockwave. I wanted to confirm if this is true.

A possible comparison may be cases of sudden cabin depressurization on airplanes, and whether injuries from those are comparable to blast injuries. Presently, I do not know of significant depressurization injuries comparable to even mild blast ones, so I suspect the idea was incorrect.

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    I think this is an interesting question, but I don't think it really meets the prior research requirements here. This site requires questions to demonstrate some degree of prior research. You can edit your question to add information to improve it. That said, you might want to look at this article, in particular Figure 3 and the following paragraphs. The negative pressure wave may be visibly impressive, but not as much when measured by pressure change.
    – Carey Gregory
    Aug 20, 2022 at 22:12
  • @CareyGregory Thank you for the source. Afraid I can't find much on this subject, despite trying to research it. Most I can off is anecdotal stuff about tests on dogs decompressing them, via NASA in the 60s. Most of them apparently survived about a minute of vacuum, with nasa deciding a person can survive for 90 seconds. This could be said to be equivalent to a 14psi explosion for over a minute; which would be totally unsurvivable in the case of a blastwave? So I think this rumour was incorrect.
    – user343708
    Aug 21, 2022 at 0:33
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    It's perfectly okay, even encouraged, to answer your own questions. So you could use that article and whatever else you've found to write an answer finding in the negative to your question. It would probably earn you some rep, particularly when you accepted your answer.
    – Carey Gregory
    Aug 21, 2022 at 2:51
  • @CareyGregory Thank you, I will.
    – user343708
    Aug 21, 2022 at 5:39

1 Answer 1

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Here's a quote from the 60s NASA study on testing rapid decompression of dogs for over a minute: https://www.reliasmedia.com/articles/4602-evaluation-and-management-of-patients-with-blast-injuries-in-the-ed

During recompression to higher pressures, the subcutaneous gases were, of course, also recompressed and the animals quickly and dramatically deflated to their normal appearance, still remaining, however, in an obvious state of flaccid paralysis, unconsciousness, and apnea. This deflation process appeared to begin rather gradually with the onset of recompression. At 25 to 30 mm. Hg absolute, deflation became more rapid ; at approximately 70 mm. Hg the animals appeared to have returned to their normal size. At 45 to 50 mm. Hg, however, a major portion of the deflation is complete, suggesting that water vapor is probably the predominant gas concerned with the excessive distention of the animals. The exact pressures at which the deflation process and the condensation of water vapor occurred was influenced, in part at least, by the subcutaneous and deep body temperatures which, in turn, were probably affected by the duration of the low pressure exposures and the evaporative cooling of the body surfaces. The rapidity of recovery during or after recompression was generally dependent on the duration of the low pressure exposure, the rate of recompression, and on whether or not the animals were recompressed with oxygen or air. As might well be expected, the shorter the exposure time and the faster the recompression with oxygen, the more rapid and less complicated was the recovery period. Animals that were exposed to the low pressure for 90 seconds or less often began to breathe spontaneously during the recompression to ground level. When the exposures to the reduced pressure were longer than 90 seconds, the depressed state of the animals was intensified and apnea persisted for a prolonged period of time after recompression. Under these conditions, when first examined at ground level, the animals were usually apneic with variations in heart rate ranging from bradycardia to tachycardia. They remained apneic for varying periods of time, but spontaneous respiration always began in less than 2 to 3 minutes, provided there was a heartbeat. Otherwise, when no heartbeat was detectable, the animals invariably failed to survive. During the course of recovery, both the heart rate and respiratory frequency increased steadily for the first 2 to 5 minutes. Some of the animals exhibited a state of decerebrate spasticity when stimulated by being touched or handled. Most of the animals started purposeful movements of the extremities and head within 10 to 15 minutes and next progressed to a stage showing disorientation, with staggering and apparent blindness. During this time, coordinated control and strength in the hind legs seemed to return much more slowly than in the forelimbs. By the end of 30 minutes, none of the animals exhibited objective neurologic abnormalities ; nevertheless, they appeared to be in a state of extreme fatigue and exhaustion and were very lethargic. The apparent blindness seemed to abate by the end of the 30th minute of recovery. Those that were exposed to the low pressure for longer than 60 seconds excreted, after recompression to ground level, an excessively large amount of clear, saliva-like fluid from the mouth; moist, basal rales were audible, suggesting pulmonary edema. By the end of 24 hours, the animals spontaneously cleared themselves of the rales and edema and appeared to have normal respiratory function and behavior.

Some of the dogs were decompressed over 0.2 seconds,, most were over 1 second, all were to about 1mm Hg. There is no special mention of the damage for the faster decompressions. With 120 sec exposure, fatality rate was 15%, with 180sec it was 80%.

At that rate, and from figure 4 of this article Carey Gregory kindly found, it seems explosive decompression is not fast enough to warrant concern compared to the blast wave. Thermobaric warheads create a vacuum for some amount of time, but even then I would only worry about it somewhat worsening existing conditions from the blast.

In various literature about blast injuries, practically no mention is made of depressurization as a factor, as well. So it seems what I heard about it was just a rumour, likely inspired by the myth of astronauts exploding in space.

I hope this was interesting to read.

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