Vent and drain lines.
CFR · 2024-01-01 · US · Title 14
All vent and drain lines, and their fittings, that are located in a designated fire zone must, if they carry flammable fluids or gases, comply with § 125.157, if the Administrator finds that the rupture or breakage of any vent or drain line may result in a fire hazard.
official document · source cfr-2024 · id 14:§ 125.159