14 CFR § 29.855

Each cargo and baggage compartment must be construced of or lined with materials in accordance with the following:

For accessible and inaccessible compartments not occupied by passengers or crew, the material must be at least fire resistant.

Materials must meet the requirements in § 29.853(a)(1), (a)(2), and (a)(3) for cargo or baggage compartments in which—

The presence of a compartment fire would be easily discovered by a crewmember while at the crewmember's station;

Each part of the compartment is easily accessible in flight;

The compartment has a volume of 200 cubic feet or less; and

Notwithstanding § 29.1439(a), protective breathing equipment is not required.

No compartment may contain any controls, wiring, lines, equipment, or accessories whose damage or failure would affect safe operation, unless those items are protected so that—

They cannot be damaged by the movement of cargo in the compartment; and

Their breakage or failure will not create a fire hazard.

The design and sealing of inaccessible compartments must be adequate to contain compartment fires until a landing and safe evacuation can be made.

Each cargo and baggage compartment that is not sealed so as to contain cargo compartment fires completely without endangering the safety of a rotorcraft or its occupants must be designed, or must have a device, to ensure detection of fires or smoke by a crewmember while at his station and to prevent the accumulation of harmful quantities of smoke, flame, extinguishing agents, and other noxious gases in any crew or passenger compartment. This must be shown in flight.

For rotorcraft used for the carriage of cargo only, the cabin area may be considered a cargo compartment and, in addition to paragraphs (a) through (d) of this section, the following apply:

There must be means to shut off the ventilating airflow to or within the compartment. Controls for this purpose must be accessible to the flight crew in the crew compartment.

Required crew emergency exits must be accessible under all cargo loading conditions.

Sources of heat within each compartment must be shielded and insulated to prevent igniting the cargo.