[Moth]

A bulk tank may not be any more susceptible to blowing up, but think of it this way:

With a bulk tank there are a lot more connections for possible leaks.

AND, if you are on a small 1 pound cylinder and it blows up--you will kill yourself. If you are on a 20# tank and it blows up- you are taking your neighbors with you.

I prefer not to blow up whether my insurance is going to pay for damages or not. LOL Safety is for your protection and the protection of those around you- not just legalities, though those are certainly important.

As far as safe working on a patio- as long as you don't have any tripping hazards (which is also relevant INDOORS...not special to your situation), your propane is outside, your oxycon is inside (for it's own longevity), you are wearing proper eyewear and the wind isn't strong enough to blow your flame sideways you should be just as safe as any of the rest of us.

Flashback arrestors are a good idea even on surface mix torches. They aren't supposed to flashback- but that doesn't mean they don't. I don't have one on my oxycon, but there is nothing wrong with putting one there. I do have one on my propane and consider it a necessity.

Your ventilation is fine. You have a better air supply than indoor ventilated. Your cfm of fresh air transfer is higher than mine. LOL

~~Mary