At ambient conditions, increased pressure and decreased temperature can liquefy acetylene. At extremely low temperatures, acetylene can solidify. The danger at the point of liquefaction or solidification (and the major reason why acetylene cannot be distributed in this form) is that the necessarily high pressures create a very unstable product. At the slightest provocation, compressed acetylene will dissociate into its chemical components, carbon and hydrogen. This dissociation is accompanied by drastic increases in both temperature and pressure, and results in an explosion. The acetylene distributor, as well as the user, must observe important precautions:
(1) Slings, hooks or magnets cannot be used to move cylinders. Cylinders of acetylene must be kept in an upright position. Cylinders cannot be dragged, and can never be used or stored in a horizontal position.
(2) A hand truck should be used when an acetylene cylinder must be moved, or the cylinder should be tilted slightly and rolled it on its bottom edge.
(3) A cylinder storage area should be chosen that is well removed from any heat sources, and the area should be posted with conspicuous signs forbidding smoking or the use of open flames or lights.
(4) If cylinders are stored outdoors, dirt, snow or ice should not be allowed to accumulate on valves or safety devices.
(5) The cylinders should be secured with chains or heavy rope so that they cannot be accidentally tipped over.
(6) A leaking cylinder must be handled with extreme care; it should be removed immediately from the storage area after checking to be sure that no sources of ignition are brought near it. The supplier should be notified immediately.
(7) One cylinder should not be recharged from another, or other gases mixed in an acetylene cylinder.
(8) Copper tubing should never be used to convey acetylene. Acetylene will react with the copper to form copper acetylide, an unstable compound which can explode spontaneously.