14 CFR § 25.1183

Except as provided in paragraph (b) of this section, each line, fitting, and other component carrying flammable fluid in any area subject to engine fire conditions, and each component which conveys or contains flammable fluid in a designated fire zone must be fire resistant, except that flammable fluid tanks and supports in a designated fire zone must be fireproof or be enclosed by a fireproof shield unless damage by fire to any non-fireproof part will not cause leakage or spillage of flammable fluid. Components must be shielded or located to safeguard against the ignition of leaking flammable fluid. An integral oil sump of less than 25-quart capacity on a reciprocating engine need not be fireproof nor be enclosed by a fireproof shield.

Paragraph (a) of this section does not apply to—

Lines, fittings, and components which are already approved as part of a type certificated engine; and

Vent and drain lines, and their fittings, whose failure will not result in, or add to, a fire hazard.

All components, including ducts, within a designated fire zone must be fireproof if, when exposed to or damaged by fire, they could—

Result in fire spreading to other regions of the airplane; or

Cause unintentional operation of, or inability to operate, essential services or equipment.