Quote Originally Posted by brk1 View Post
.....yet when you release the FX drain plug where the first set of magic glass beads are , you can feel the wet air shoot out when you undo it , When you release the valve the air always feels cold , yet when you compress the air it heats up, .....
The air is at room temperature and at very high pressure before it's released. The increase in temperature which occured while it was being [slowly] compressed has been given up as heat to its surroundings.

This air has some water vapour in it. If the air is very suddenly allowed to expand into the room it will cool very rapidly - the explanation for that is in my sig file - the general gas equation. When the air very rapidly cools it can no longer hold a small amount of water in it as vapour. The water vapour condenses into fine droplets. That's why you experience cold wet air on release.