There once was in Carrollton, Texas, at the intersection of Belt Line Road and Webb Chapel Road a concern called Otis Engineering. I was by there for a visit. They made “down-line” equipment for oil wells. This was stuff that went down into oil wells, sometimes miles deep, to make measurements and such.
They had a pressure chamber for testing their stuff, and this chamber was well-armored, to withstand those deep pressures. They filled it with water and applied the pressure. They took great care that there was no air in the chamber. Why was that. What would be the problem if there were some air in the pressure chamber?
This one is some basic science and I expect some quick answers. Provide your response in the comments section below.
Update and answer
Greg has answered this one, but I do not see evidence he has posted a comment. The reason is this:
A body of water under pressure represents an amount of stored energy to the extent it is compressed. Air is multiply-compressible over water, and at great pressures can story a dangerous amount of energy. The potential energy of a compressed fluid is proportional to the pressure and the square of the compressed volume. Since water compresses very little under great pressure, compressed water does not represent so much potential energy. Any gas in the chamber, however, would be compressed tremendously and would represent a large amount of potential energy.
Greg is correct in that it would take more energy to raise the pressure of the chamber if had some air in it. However, the real concern is the danger of releasing the potential energy accidentally.