This publication has been prepared as a guide for the inspection and requalification of the acetylene cylinder shell and porous mass. It should be of interest to acetylene cylinder manufacturers, acetylene production and distribution personnel, welding gas distributors, safety personnel and users of acetylene. This publication covers both a thorough, external prefill visual inspection of acetylene cylinders and the periodic inspections of the cylinder shell and porous mass which are required for acetylene cylinder requalification.