Originally Posted by neilzero

The last I heard pressure in low Earth obit is about one millionth PSI About because most gauges don't measure that low = read zero, so pressure must be inferred from how many particles per minute hit a target of perhaps one square inch and estimates of their speed, complicated by the target moving almost 18,000 miles per hour, with respect to Earth's surface.
The pressure in the space shuttle drops to about 10 psi with the oxygen enriched from 21% to about 25% in orbit. About the same for ISS. Mir was lower pressure: about 7 psi with oxygen enrichment at about 50%. Lower pressure is possible, and is used for EVA = extravehicular activities = space suits, but water vapor is low, and causes chapped lips, condensation and other problems.
psig = pounds per square inch with a gauge can read as much as negative 15 psi in a vacuum container at sea level, but this this terminology is rarely used in orbit or even for high flying aircraft so we could say there is no such thing as negative pressure.
I don't think any humans have been subjected to 100 atmospheres. 50X maybe. The container would be very costly, but I suppose a few have been built that would just barely hold one human. 100 atmospheres would be fatal unless approached gradually over many hours, and even more hours to return to one atmosphere even breathing helium or hydrogen instead of nitrogen. Apparently helium and hydrogen are less likely to produce bubbles in the tiny capillaries, which causes bends. Some of the above is guessing, so please correct where I am wrong. Neil