The tanks need to stand so they won't become projectiles, if they roll away and the valve gets broken or sheared. They should be standing and strapped to something solid if not placed in a cart. The o2 is high pressure, the acetylene tank is filled with a foam/sponge like material. Laying the acetylene on its side, some of the foam my float into your valve clogging it, making fora hard time to get a consisant flame. I'm sure you can view some videos on you tube with tanks going through the roof, or though block walls...