I am writing on this subject because I saw a report on CNN discussing an explosion in the back of a car set off by energizing the electric trunk latch. It blew off the trunk and mangled the rear end of the car. Fortunately, nobody was hurt, but the possibility of a lethal accident was certainly there. The fireman that is interviewed mentions that there was an acetylene cylinder in the back of the car which leaked, and the trunk latch set it off. The acetylene should not have been there at all. Acetylene cylinders contain liquid acetone that is stabilized in a porous, cement like material. The acetone is there to dissolve the acetylene gas stored in the cylinder. Acetylene gas is unstable above 15 psig, but must be stored at a much higher pressure to store enough for practical use. Dissolving it in the acetone allows the higher pressure without creating a bomb. The cylinder regulator reduces the acetylene pressure to less than 15 psig. The actual pressure depends on the regulator setting. Note that you should NEVER adjust an acetylene regulator to a pressure above 15 psig.
Since acetylene cylinders contain liquid acetone, they should NEVER be laid on their side. They should ALWAYS be transported in the vertical position, securely fastened to the vehicle. Laying an acetylene cylinder on its side can result in the liquid acetone leaking out into the valve and regulator – setting up a very hazardous situation. You also should not have cylinders in the back seat behind you. Not just for the explosion hazard, but also because of the shifting weight in case of an accident. Any heavy objects behind you will crush you in an accident. My wife’s cousin was killed many years ago transporting cylinders in the back of his car. They crushed him in an accident that would otherwise probably not have killed him. That is why working trucks have a metal cage between the driver and the stuff in the back – to save your life in an accident. Basically, what this all means is that THERE IS NO SAFE WAY to carry an acetylene cylinder in your Prius! If you are going to transport torches or cylinders, you need a properly outfitted truck – not your family sedan.