Explosions@ fires@ and health hazards may result if welding@ cutting@ or other hot work is performed on containers that are not free of hazardous substances@ such as combustible@ reactive@ or toxic solids@ liquids@ vapors@ dusts@ and gases. No container should be presumed to be clean or safe@ but containers can be made safe for work@ provided the recommendations or their equivalent prescribed herein are followed.These recommendations should apply to the preparation for welding of metal containers and piping. For the purposes of this document@ references to precautions for welding are also intended to apply to all metal working operations (such as cutting or brazing) involving the application of heat. Cleaning of used containers is necessary in all cases before welding. The term container@ as used herein@ includes piping.The safe practices recommended here are not intended to replace either regulatory standards or more stringent practices of industries that have expert knowledge of handling hazardous substances. Consequently@ safe practices recommended here are not intended to apply to the following:1(1) Containers and confined spaces that can be entered by workers(2) Containers that have contained radioactive substances(3) Compressed gas containers(4) Containers that have held explosive substances (such as nitrocellulose@ pyroxylin solution@ etc.) (5) Tanks@ bunkers@ or compartments on ships (6) Gasometers or gas holders for natural and manufactured gases(7) Outside@ above-ground@ vertical petroleum storage tanks (8) Containers holding flammables that are to be repaired while in service1. See Annex A@ Bibliography.