Last night when I went to inspect the air plumbing in my shop I noticed that half the shop is plumbed with PVC pipe!!!!
Fortunately, its exactly 1/2, it's the half I care much less about having air in, the half I _do_ care about is black iron, and there's just one little join between sections -- so not only can I isolate it fairly easily, but I now have a really generous supply of female air fittings.