This standard informs the reader of the necessary safe practices to be followed in the cleaning and preparation of containers and piping for welding or cutting. It describes various methods for cleaning, including water, steam, hot chemical, and mechanical, and techniques to be used for their proper preparation, such as inerting. Consequently, safe practices presented here are not intended to apply to the following: (1) Containers and confined spaces that can be entered by workers (see ANSI Z117.1, Safety Requirements for Confined Spaces2), (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 service.