In the mid 70's I got my own torch, and became a passable oxy/acet welder for things like exhaust, and at the time became fair at cutting. (Not so much anymore, LOL) In my HVAC days, of course used one a lot for brazing. I HAVE NEVER REALLY KNOWN THE ANSWER TO THIS............ I realize acetylene must be used upright, but sometimes you must transport it lying down. WHAT IS THE TIME necessary to leave a bottle upright before use? 1 minute? 5? 5,000,000?