In fact PVC piping is prohibited for use in compressed gas systems (including compressed air) by OSHA. Here's a link:
OSHA's stance on PVC
It's a shrapnel hazard when it fails, very dangerous stuff! I know some people have gotten away with it for years without incident, but when it does fail, it isn't pretty.
Copper or Black iron pipe isn't that much more expensive and not that hard to work with. I plumbed my 32 x 34 shop w/ 1/2" black iron pipe in a few hours with a chop saw and a rented pipe threader.
Just wanted to share some info.