(Back after a brief Hiatus.)
HOW NOT TO MAKE AN OXY-ACETYLENE "DEVICE":
1. Do NOT establish a neutral flame with your oxy-acetylene rig.
2. Do NOT extinguish the flame by snuffing it out on a metal surface. (Or turning the acetylene off and then back on.)
3. Do NOT allow the (now non-burning) gasses to fill some sort of container. (Hint: Little dab'll do ya! This means NOT VERY BIG.)
4. Do NOT set it in an open area with some sort of fuse (burning paper towel or whatever.)
5. DO run like hell and cover your ears.