1910.252(a)(2)(vi) Prohibited areas. Cutting or welding shall not be permitted in the following situations:…1910.252(a)(2)(vi)(C) In the presence of explosive atmospheres (mixtures of flammable gases, vapors, liquids, or dusts with air), or explosive atmospheres that may develop inside uncleaned or improperly prepared tanks or equipment which have previously contained such materials, or that may develop in...