Propane by design is fairly safe - an odorant called a mercaptan is injected into it to give it a rotten egg smell for leak detection (same with natural gas), and the tanks are fitted with excess flow checks that will automatically stop the flow if a line is severed. However, to work properly, this feature requires that the valves not be restricted, meaning they should be left wide open so that the checks will function. The main concern when fueling is the open flame in the event of a gasoline spillage....
3 tons