[weldtoride]

Much to be said about storing unused fuel tanks outside, very simple to do. However, there is a lot of work to plumb it correctly to inside to the building. And as Marty says, if it isn't done correctly you may have created a new hazard...

I would minimally include a water flashback arrestor inside, along with an inside shut off also. You cannot run outside quickly to give your acetylene tank valve the quarter or half twist to close it in an emergency. I had an acetylene regulator diaphragm fail suddenly at home several years ago. Thankfully I was immediately aware and that quick half twist kept the drama to a minimum. Inside shut offs also necessary for a burning hose, or a burn back. Again, your welding supplier can put you in touch with the people who design these systems.

Tanks do have some safety devices built-in. Non-fuel, high pressure tanks like Oxygen, MIG, and TIG, etc. have a pressure relief built into the valve. In a fire, with the obvious exception of oxygen tanks, I would think they would act as inhibitors once the relief pops off, due to heat expansion causing pressure rise in the tank. Obviously oxygen tanks are accelerants once they pop off.

Acetylene tanks have fusible plugs that are designed to melt and allow gas to escape in a stream (theoretically) instead of building to one really big bang.

A compromise might be to switch to smaller O/A tanks, keep all but the two you are using outside in the bunker. Or get some large diameter steel wheels and wheel your kit after use out to the bunker.