I've been a mechanic since leaving college over 30 years ago and currently work with hydraulics and LPG systems all day in the world of forklifts. A bit of CO2 holds no fear for me. I'm well aware of the precautions you need to take around this kind of stuff, but didn't know if anyone had done a walkthrough of how to build such a system. Yes, the pressures in a CO2 bottle are higher, but at least it's not flammable!