CFR›Title 30›Chapter I›Part 57›Subpart T›Subject Group Underground Retorts ContainsSection 57.22401CorpusDaily eCFRDisplayed edition2026-04-24Last updated2026-04-24 Sections 57.22401 § 57.22401 Underground retorts (I-A and I-B mines). Previous Mine Categorization Mine Categorization Next Ventilation Ventilation