when testing Industrial hoses for pressure only a fool would use compressed air. if an end lets go or the hose fails , Air goes off like a bomb so Air is not used to test. Water and ONLY water is used as if there is a failure as above, you will get wet and thats all. Water being a liquid absorbs the energy and releases it in a more linear way.
Think about your safety and the safety of everyone in the block as Ive seen just how far a projectile can travel when an oversize air rifle goes off without warning.