14 CFR §121.261
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
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 § 121.259, if the Administrator finds that the rupture or breakage of any vent or drain line may result in a fire hazard.