§ 121.247 – Firewall construction.
Each fire wall and shroud must—
(a) Be so made that no hazardous quantity of air, fluids, or flame can pass from the engine compartment to other parts of the airplane;
(b) Have all openings in the fire wall or shroud sealed with close-fitting fireproof grommets, bushings, or firewall fittings;
(c) Be made of fireproof material; and
(d) Be protected against corrosion.