|Warning Disclaimer - I don't suggest trying to make one of these yourself.
A pressure chamber can explode causing serious injury or death. (PVC pipe tends to shatter into small splinters or shrapnel when it explodes and not all PVC is pressure rated.
NEVER pressurize PVC pipe with air, hydro-testing (water) is the only way it should be done. If you don't know what that means DON'T TRY IT, PERIOD.