14 C.F.R. § 25.1017 Oil lines and fittings.
Title 14 - Aeronautics and Space
(a) Each oil line must meet the requirements of §25.993 and each oil line and fitting in any designated fire zone must meet the requirements of §25.1183. (b) Breather lines must be arranged so that— (1) Condensed water vapor that might freeze and obstruct the line cannot accumulate at any point; (2) The breather discharge does not constitute a fire hazard if foaming occurs or causes emitted oil to strike the pilot's windshield; and (3) The breather does not discharge into the engine air induction system.
Title 14: Aeronautics and Space
PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
Subpart E—Powerplant
Oil System
§ 25.1017 Oil lines and fittings.