Good ideas, all. Most hairspray cannons are made of PVC or ABS plastic. Steel would be much less likely to fragmentate, but if it did... Ouch. I usually dont take risks like that. When I was testing my air powered steel one, I hooked it up to the compressore (at 0 psi) and put it outside on the left side of my garage. I then turned the breaker to the garage off, turned the compressor on, went to the right side of my garage and flipped the breaker back on. You can call it overcautious, but Im still alive. =)