14 CFR § 25.855

The compartment must meet one of the class requirements of § 25.857.

Each of the following cargo or baggage compartments, as defined in § 25.857, must have a liner that is separate from, but may be attached to, the airplane structure:

Any Class B through Class E cargo or baggage compartment, and

Any Class F cargo or baggage compartment, unless other means of containing a fire and protecting critical systems and structure are provided.

Ceiling and sidewall liner panels of Class C cargo or baggage compartments, and ceiling and sidewall liner panels in Class F cargo or baggage compartments, if installed to meet the requirements of paragraph (b)(2) of this section, must meet the test requirements of part III of appendix F of this part or other approved equivalent methods.

All other materials used in the construction of the cargo or baggage compartment must meet the applicable test criteria prescribed in part I of appendix F of this part or other approved equivalent methods.

No compartment may contain any controls, 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.

There must be means to prevent cargo or baggage from interfering with the functioning of the fire protective features of the compartment.

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

Flight tests must be conducted to show compliance with the provisions of § 25.857 concerning—

Compartment accessibility,

The entries of hazardous quantities of smoke or extinguishing agent into compartments occupied by the crew or passengers, and

The dissipation of the extinguishing agent in all Class C compartments and, if applicable, in any Class F compartments.

During the above tests, it must be shown that no inadvertent operation of smoke or fire detectors in any compartment would occur as a result of fire contained in any other compartment, either during or after extinguishment, unless the extinguishing system floods each such compartment simultaneously.

Cargo or baggage compartment electrical wiring interconnection system components must meet the requirements of § 25.1721.