14 CFR 29.1017 - Oil lines and fittings.
(a) Each oil line must meet the requirements of § 29.993.
(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 will not constitute a fire hazard if foaming occurs, or cause emitted oil to strike the pilot's windshield; and
(3) The breather does not discharge into the engine air induction system.