Hello Katherine, Your posting is valuable to other forum users from a safety point of view. The only way combustion could take place within the torch body is if fuel is present in the torch. For fuel (Acetylene) to be present there must be a leak in the torch valve or you did not turn it off completely. Your tuition is the best indicator here. The torch is 50ish years old and does not owe you anything. If you change to propane or butane you might miss the heat acetylene produces. If you are enameling or annealing large pieces the propane and butane might not do it for you. Best to test these pieces of equipment first if you can. The issue of acetylene producing smoke is easily overcome by introducing a small amount of oxygen before igniting. I don’t know about the acetylene/air mix. I have all three fuel sources and prefer oxy/acetylene for its versatility. Keith