I won't bore everyone to tears with applications of the Ideal Gas Law (PV=nRT and so on) and go running for my thermodynamics book that is still packed away. I'll just recall from memory a computation we did in thermo class oh-so-long-ago on compressed air at about 10 times nominal atmospheric pressure. "Standard" atmospheric pressure at sea level is about 14.7 PSI, or 101,300 Pascals.

So 10 * 1 atmosphere is about 147 psi, or about 1,000 kPa. I don't remember the size of the vessel just now, but it was a size that wasn't unreasonable to see in an garage or shop, and that's how we decided on about 10 * standard atmospheric pressure. I remember the exercise was inspired by a news article where someone was killed.

I seem to recall the exercise was a vessel that contained about 10 kg of compressed air, at 10 atm's. At that compression, in an ideal world, the compressed air would hold about 100 kJ of energy per kg of air, or 100 * 10 or 1,000 kJ of energy.

The resulting release of energy was roughly equivalent to about 0.25kg of TNT. From somewhere, I also seem to recall that an old-fashioned stick of dynamite is roughly about 1,000 kJ of energy. This was my lasting memory -- a two-stage air compressor with a big tank is roughly equivalent to a stick of dynamite -- wrapped in steel for extra shrapnel.

Perhaps Franz can comment on what 0.25kg (about 0.5lb+) of TNT looks like when set off.

When pressure vessels are tested for working pressure and burst pressure, they don't use compressed air -- they use water. They fill the vessel with water, put the water under pressure and test per requirements. Because you can't compress a fluid, you can't store anywhere near the energy in a fluid that you can in a gas. Once the vessel ruptures under fluid pressure, pfft, the pressure is released because the only stored energy was in the flexing of the vessel walls, which wasn't much. Net:net -  you go get a mop and live with the result.

It's your call Mike, but my perspective is that there's one heck of a large snake coiled and waiting to strike inside compressed air vessels.