---
kind: "range"
citation: "14 C.F.R. §§ 25.1181–25.1191"
title: "14"
from: "25.1181"
to: "25.1191"
count: 7
url: "https://uscodex.org/cfr/14/25.1181..25.1191"
---

# §25.1181. Designated fire zones; regions included.

- (a) **Designated fire zones are—**
  - (1) The engine power section;
  - (2) The engine accessory section;
  - (3) Except for reciprocating engines, any complete powerplant compartment in which no isolation is provided between the engine power section and the engine accessory section;
  - (4) Any auxiliary power unit compartment;
  - (5) Any fuel-burning heater and other combustion equipment installation described in [§ 25.859](/cfr/14/25.859.md);
  - (6) The compressor and accessory sections of turbine engines; and
  - (7) Combustor, turbine, and tailpipe sections of turbine engine installations that contain lines or components carrying flammable fluids or gases.
- (b) Each designated fire zone must meet the requirements of §§ [25.863](/cfr/14/25.863.md), [25.865](/cfr/14/25.865.md), [25.867](/cfr/14/25.867.md), [25.869](/cfr/14/25.869.md), and [25.1185 through 25.1203](/cfr/14/25.1185..25.1203.md).

# §25.1182. Nacelle areas behind firewalls, and engine pod attaching structures containing flammable fluid lines.

- (a) Each nacelle area immediately behind the firewall, and each portion of any engine pod attaching structure containing flammable fluid lines, must meet each requirement of §§ [25.1103(b)](/cfr/14/25.1103.md?p=b), [25.1165 (d)](/cfr/14/25.1165.md?p=d) and [(e)](/cfr/14/25.1165.md?p=e), [25.1183](/cfr/14/25.1183.md), [25.1185(c)](/cfr/14/25.1185.md?p=c), [25.1187](/cfr/14/25.1187.md), [25.1189](/cfr/14/25.1189.md), and [25.1195 through 25.1203](/cfr/14/25.1195..25.1203.md), including those concerning designated fire zones. However, engine pod attaching structures need not contain fire detection or extinguishing means.
- (b) For each area covered by [paragraph (a)](#a) of this section that contains a retractable landing gear, compliance with that paragraph need only be shown with the landing gear retracted.

# §25.1183. Flammable fluid-carrying components.

- (a) Except as provided in [paragraph (b)](#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.
- (b) **Paragraph (a) of this section does not apply to—**
  - (1) Lines, fittings, and components which are already approved as part of a type certificated engine; and
  - (2) Vent and drain lines, and their fittings, whose failure will not result in, or add to, a fire hazard.
- (c) All components, including ducts, within a designated fire zone must be fireproof if, when exposed to or damaged by fire, they could—
  - (1) Result in fire spreading to other regions of the airplane; or
  - (2) **Cause unintentional operation of, or inability to operate, essential services or equipment.**

# §25.1185. Flammable fluids.

- (a) Except for the integral oil sumps specified in [§ 25.1183(a)](/cfr/14/25.1183.md?p=a), no tank or reservoir that is a part of a system containing flammable fluids or gases may be in a designated fire zone unless the fluid contained, the design of the system, the materials used in the tank, the shut-off means, and all connections, lines, and control provide a degree of safety equal to that which would exist if the tank or reservoir were outside such a zone.
- (b) There must be at least one-half inch of clear airspace between each tank or reservoir and each firewall or shroud isolating a designated fire zone.
- (c) Absorbent materials close to flammable fluid system components that might leak must be covered or treated to prevent the absorption of hazardous quantities of fluids.

# §25.1187. Drainage and ventilation of fire zones.

- (a) There must be complete drainage of each part of each designated fire zone to minimize the hazards resulting from failure or malfunctioning of any component containing flammable fluids. The drainage means must be—
  - (1) Effective under conditions expected to prevail when drainage is needed; and
  - (2) Arranged so that no discharged fluid will cause an additional fire hazard.
- (b) Each designated fire zone must be ventilated to prevent the accumulation of flammable vapors.
- (c) No ventilation opening may be where it would allow the entry of flammable fluids, vapors, or flame from other zones.
- (d) Each ventilation means must be arranged so that no discharged vapors will cause an additional fire hazard.
- (e) Unless the extinguishing agent capacity and rate of discharge are based on maximum air flow through a zone, there must be means to allow the crew to shut off sources of forced ventilation to any fire zone except the engine power section of the nacelle and the combustion heater ventilating air ducts.

# §25.1189. Shutoff means.

- (a) Each engine installation and each fire zone specified in § [25.1181(a)(4)](/cfr/14/25.1181.md?p=a-4) and [(5)](/cfr/14/25.1181.md?p=a-5) must have a means to shut off or otherwise prevent hazardous quantities of fuel, oil, deicer, and other flammable fluids, from flowing into, within, or through any designated fire zone, except that shutoff means are not required for—
  - (1) Lines, fittings, and components forming an integral part of an engine; and
  - (2) Oil systems for turbine engine installations in which all components of the system in a designated fire zone, including oil tanks, are fireproof or located in areas not subject to engine fire conditions.
- (b) The closing of any fuel shutoff valve for any engine may not make fuel unavailable to the remaining engines.
- (c) Operation of any shutoff may not interfere with the later emergency operation of other equipment, such as the means for feathering the propeller.
- (d) Each flammable fluid shutoff means and control must be fireproof or must be located and protected so that any fire in a fire zone will not affect its operation.
- (e) No hazardous quantity of flammable fluid may drain into any designated fire zone after shutoff.
- (f) There must be means to guard against inadvertent operation of the shutoff means and to make it possible for the crew to reopen the shutoff means in flight after it has been closed.
- (g) Each tank-to-engine shutoff valve must be located so that the operation of the valve will not be affected by powerplant or engine mount structural failure.
- (h) Each shutoff valve must have a means to relieve excessive pressure accumulation unless a means for pressure relief is otherwise provided in the system.

# §25.1191. Firewalls.

- (a) Each engine, auxiliary power unit, fuel-burning heater, other combustion equipment intended for operation in flight, and the combustion, turbine, and tailpipe sections of turbine engines, must be isolated from the rest of the airplane by firewalls, shrouds, or equivalent means.
- (b) Each firewall and shroud must be—
  - (1) Fireproof;
  - (2) Constructed so that no hazardous quantity of air, fluid, or flame can pass from the compartment to other parts of the airplane;
  - (3) Constructed so that each opening is sealed with close fitting fireproof grommets, bushings, or firewall fittings; and
  - (4) **Protected against corrosion.**