[Synchro909]

My answer to those concerned about a tank exploding while they are soldering it is firstly, soldering won't get hot enough to cause ignition and secondly, from school science classes when I was about 14 years old, combustion needs 3 things to happen ALL AT ONCE. They are the presence of fuel, oxygen and a source of ignition. (You'd have the ignition temperatures if you were welding.) If any one of those things is missing, combustion - read explosion, can't happen. The easiest one to eliminate is oxygen and the easiest way to do that in this scenario is to have an engine running nearby and run a hose from its exhaust into the tank. With the motor running, the tank is full of exhaust fumes, which we know are devoid of oxygen. Run the motor for a few minutes before starting to weld and don't breathe the exhaust.