30 CFR 57.4604 : Mineral Resources (§ 1.1 To Parts 1291-1299) — (§ 1.1 To Parts 105-199) — Mine Safety And Health Administration, Department Of Labor (§ 1.1 To Parts 105-199) — Metal And Nonmetal Mine Safety And Health (§ 56.1 To § 58.620) — Safety And Health Standards - Underground Metal And Nonmetal Mines (§ 57.1 To Appendix I To Subpart T Of Part 57) — Fire Prevention And Control (§ 57.4000 To Appendix I To Subpart C Of Part 57) — Welding/Cutting/Compressed Gases (§ 57.4600 To § 57.4660) — Preparation of pipelines or containers.

Before welding, cutting, or applying heat with an open flame to pipelines or containers that have contained flammable or combustible liquids, flammable gases, or explosive solids, the pipelines or containers shall be -

(a) Drained, ventilated, and thoroughly cleaned of any residue;

(b) Vented to prevent pressure build-up during the application of heat; and

(c)(1) Filled with an inert gas or water, where compatible; or

(2) Determined to be free of flammable gases by a flammable gas detection device prior to and at frequent intervals during the application of heat.