(a) All crew compartments shall be ventilated by providing a sufficient amount of fresh air to enable the crew members to perform their duties without undue discomfort or fatigue.

NOTE: An outside air supply of approximately 10 cubic feet per minute is considered a minimum for each crew member.

(b) Ventilating air in crew and passenger compartments shall be free of harmful or hazardous concentrations of gases or vapors.

NOTE: Carbon monoxide concentrations in excess of one part in 20,000 parts of air are considered hazardous. Carbon dioxide in excess of 3 percent by volume (sea level equivalent) is considered hazardous in the case of crew members. Higher concentrations of carbon dioxide may not necessarily be hazardous in crew compartments if appropriate protective breathing equipment ls available.

(c) Provision shall be made to insure the conditions prescribed in paragraph (b) of this section in the event of reasonably probable failures or malfunctioning of the ventilating, heating, pressurization, or other systems and equipment. If accumulation of hazardous quantities of smoke in the cockpit area is reasonably probable, smoke evacuation shall be readily accomplished starting with full pressurization and without depressurizing beyond safe limits (see § 4b.374(b)).

NOTE: Examples of acceptable provisions include secondary isolation, integral protective devices, and crew warning and shutoff for equipment the malfunctioning of which could introduce harmful or hazardous quantities of smoke or gases.

(d) Where partitions between compartments are equipped with louvres or other means allowing air to flow between such compartments, provision convenient to the crew shall be made for stopping the flow of air through the louvres or other means when such action is found necessary. (See also § 4b.357.)

(e) Means shall be provided to enable the crew to control the temperature and quantity of ventilating air supplied to the crew compartment independently of the temperature and quantity of ventilating air supplied to other compartments.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-6, 17 F. R. 1094, Feb. 5, 1952; Amdt. 4b-8, 18 F.R. 2215, Apr. 18, 1953; Amdt. 4b-6, 22 F.R. 5565, July 16, 1957]

§ 4b.371-1 Carbon monoxide detection (FAA policies which apply to § 4b.371).

Policies outlined in § 4b.467-1 will apply.

[Supp. 24, 19 F.R. 4463, July 20, 1954]

§ 4b.372 Heating systems.

Combustion heaters shall be of an approved type and shall comply with the fire protection requirements of § 4b.386. Engine exhaust heaters shall comply with the provisions of § 4b.467 (c) and (d).

[Amdt. 4b-6, 17 F. R. 1094, Feb. 5, 1952] § 4b.372-1 Combustion

heaters equipped with carbon dioxide fire extinguishers (FAA policies which apply to § 4b.372).

The policies outlined in § 4b.484-1 apply.

[Supp. 24, 19 F. R. 4463, July 20, 1954]
§ 4b.373 Pressurized cabins; general.

The design of pressurized cabins shall comply with the requirements of §§ 4b.374 through 4b.376. (See also §§ 4b.216 (c) and 4b.352, and the oxygen requirements of the appropriate operating parts of the Civil Air Regulations.) [15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-2, 20 F. R. 5306, July 26, 1955] § 4b.374 Pressure equipment and supply.

(See § 4b.477(c).

(a) Occupied cabins or compartments of airplanes shall be equipped to provide a cabin pressure altitude of not more than 8,000 feet at the maximum operating altitude of the airplane under normal operating conditions.

(b) Airplanes certificated for operation at altitudes over 25,000 feet shall be capable of maintaining a cabin pressure altitude of not more than 15,000 feet in the event of any reasonably probable failure or malfunction in the pressurization system.

[Amdt. 4b-6, 22 F. R. 5565, July 16, 1957] § 4b.375

Pressure control.

Pressurized cabins shall be provided with at least the following valves, controls, and indicators for controlling cabin pressure.

(a) Two pressure relief valves, at least one of which is the normal regulating valve, shall be installed to limit automatically the positive pressure differen

(b) Built-in fire extinguishers. Where a built-in fire extinguishing system is required, its capacity in relation to the compartment volume and ventilation rate shall be sufficient to combat any fire likely to occur in the compartment. All built-in fire extinguishing systems shall be so installed that any extinguisher agent likely to enter personnel compartments will not be hazardous to the occupants and that discharge of the extinguisher cannot result in structural damage. (See also § 4b.371.)

(c) Protective breathing equipment. If the airplane contains Class A, B, or E cargo compartments (see § 4b.383), protective breathing equipment shall be installed for the use of appropriate crew members. (See § 4b.651 (h).)

[Amdt. 4b-6, 17 F.R. 1094, Feb. 5, 1952, as amended by Amdt. 4b-7, 17 F.R. 11631, Dec. 20, 1952; Amdt. 4b-10, 24 F.R. 3153, Apr. 23, 1959]

§ 4b.380-1 Protective breathing equipment (FAA policies which apply to § 4b.380 (c)).

The policies outlined in § 4b.651-2 apply.

[Supp. 24, 19 F.R. 4463, July 20, 1954]

§ 4b.380-2 Approved hand fire extinguishers (FAA policies which apply to § 4b.380 (a)).

(a) Standards for approval. An approved type fire extinguisher includes those approved by the Underwriters Laboratories, Inc., Factory Mutual Laboratories, Underwriters' Laboratories of Canada, or any other agency deemed qualified by the Administrator, or approved by the Administrator in accordance with the provisions of § 4b.18.

(b) General. When selecting a hand fire extinguisher for use in aircraft, consideration should be given to the most appropriate extinguishing agent for the type and location of fires likely to be encountered. Consideration should also

1 Class A fires: Fires in ordinary combustible materials where the quenching and cooling effects of quantities of water, or solutions containing large percentages of water, are of first importance.

Class B fires: Fires in flammable liquids, greases, etc., where a blanketing effect is essential.

Class C fires: Fires in electrical equipment, where the use of a nonconducting extinguishing agent is of first importance.

be given to the agent's ratio of extinguishing ability to quantity required, toxicity, corrosive properties, freezing point, and to the unit's gross weight, ease of operation, and maintenance requirements. Aircraft hand fire extinguishers using agents having a rating in toxicity Group 4 or under should not be installed in airplanes for which an application for a type certificate was made on or after March 5, 1952.

(c) Types of extinguishers—(1) Carbon dioxide extinguishers.* Carbon dioxide extinguishers are acceptable when the principal hazard is a Class B or Class C fire. Carbon dioxide portable installations should not exceed five pounds of agent per unit to insure extinguisher portability and to minimize crew compartment CO, concentrations.

(2) Water extinguishers." Water extinguishers are acceptable when the principal hazard is a Class A fire and where a fire might smolder if attacked solely by such agents as carbon dioxide or dry chemical.

2 The toxicity ratings listed by the Underwriters' Laboratories for some of the commonly known fire extinguisher chemicals are as follows:

Bromochloromethane Group 3.
Bromotrifluoromethane Group 6.
Carbon dioxide Group 5.

Carbon tetrachloride Group 3.
Dibromodifluoromethane Group 4.
Methyl bromide-Group 2.

8

• Many transport type airplanes, due to their type certification basis, are not required to comply with § 4b.380. For such airplanes, it is recommended that hand fire extinguishers employing agents in toxicity Group 4 or higher be installed when renewing or replacing hand fire extinguishers employing toxic agents.

Carbon dioxide is noncorrosive and will not injure food or fabric. Extinguishers must be winterized if they are to operate at temperatures below -40° F. Approved unit capacity ranges upwards from two pounds. These extinguishers have only limited value for the extinguishment of Class A fires, the action of the agent being to blanket the fire by excluding oxygen.

Certain antifreeze agents may be corrosive. Approved extinguishers are either protected against freezing to -40° F. or must be handled as any other unprotected water on the airplane. Technical Standard Order C19a (14 CFR 514.19a) covers a minimum 1% quart capacity approved water extinguisher. Water extinguishers of the kinds currently on the market are not acceptable for flammable liquid or electrical fires.

(3) Vaporizing liquid extinguishers." Vaporizing liquid type fire extinguishers are acceptable when the principal hazard is a Class B or Class C fire.

(4) Dry chemical extinguishers.' Dry chemical extinguishers are acceptable where the principal hazard is a Class B or Class C fire. The extinguisher should not be used in crew compartments because of interference with visibility during discharge and because of the possibility of the nonconductive powders' being discharged on electrical contacts not otherwise involved.

[Supp. 30, 21 F. R. 5735, Aug. 7, 1956]
§ 46.381 Cabin interiors.

All compartments occupied or used by the crew or passengers shall comply with the following provisions:

(a) The materials in no case shall be less than flash-resistant.

(b) The wall and ceiling linings, the covering of all upholstering, floors, and furnishings shall be flame-resistant.

(c) Compartments where smoking is to be permitted shall be equipped with ash trays of the self-contained type which are completely removable. All other compartments shall be placarded against smoking.

(d) All receptacles for used towels, papers, and waste shall be of fire-resistant material, and shall incorporate covers or other provisions for containing possible fires.

(e) At least one hand fire extinguisher shall be provided for use by the flight crew.

(f) In addition to the requirements of - paragraph (e) of this section at least the - following number of hand fire extinguishers conveniently located for use in passenger compartments shall be pro

•These agents are not normally corrosive to aircraft structure and approved units will be satisfactorily protected against freezing to at least -40° F. Up to the effective date of this policy, no vaporizing liquid extinguisher with Underwriters' Laboratories toxicity rating higher than Group 4 is commercially available. Approved units have a minimum capacity of one quart. They are of only limited value for the extinguishment of Class A fires, having a cooling effect of about onetenth that of water.

The powder is nontoxic and noncorrosive and approved units are protected against freezing to at least -40° F. Minimum capacity of approved units is two pounds.

[15 F. R. 3543, June 8, 1950, as amended by Amdt. 4b-6, 17 F. R. 1094, Feb. 5, 1952]

§ 4b.381-1 Hand fire extinguishers for cabin interiors (FAA policies which apply to § 4b.381 (e) and (f)).

(a) Crew compartment. At least one hand fire extinguisher suitable for Class B and C fires should be installed in the crew compartment. Additional extinguishers may be required as dictated by potential fire hazards, extinguisher accessibility, and agent capacity.

(1) The extinguisher(s) should be readily accessible to crew members and mounted so as to facilitate quick removal from its mounting bracket.

(b) Passenger compartments. Fire extinguisher type and capacity should be based on the hazard, e. g., if a unit must protect large accessible baggage compartments, galleys, or electrical equipment racks, portables larger than minimum size should be provided. The size of the extinguisher should not, however, preclude ready portability by a flight attendant or even a passenger.

(1) Each fire extinguisher should be located adjacent to the most prominent hazard such as a baggage compartment, galley, etc.

(i) Where no such obvious hazard exists, or when only one unit is required, the extinguisher should be located at the flight attendant's station or at the entrance door on aircraft with no flight attendant.

(ii) Where two or more extinguishers are required and location is not dictated by special hazards, the units should be located at opposite ends of the passenger cabin.

(2) An extinguisher should be installed in each separate cabin, lounge, or smoking compartment unless the extinguisher in the adjacent compartment is in close proximity and easily accessible.

(3) All extinguishers should be easily accessible and clearly visible to the crew

(a) Cargo and baggage compartments shall include no controls, wiring, lines, equipment, or accessories the damage or failure of which would affect the safe operation of the airplane, unless such items are shielded, isolated, or otherwise protected so that they cannot be damaged by movement of cargo in the compartment, and so that any breakage or failure of such item will not create a fire hazard.

(b) Provision shall be made to prevent cargo or baggage from interfering with the functioning of the fire-protective features of the compartment.

(c) All materials used in the construction of cargo or baggage compartments, including tie-down equipment, shall be flame-resistant.

(d) Sources of heat within the compartment shall be shielded and insulated to prevent igniting the cargo.

NOTE: Sources of heat likely to ignite cargo include light bulbs, combustion heaters, heater ducts, electrical appliances, etc.

[15 F.R. 3543, June 8, 1950, as amended by Amdt. 4b-10, 24 F.R. 3153, Apr. 23, 1959] § 4b.383 Cargo compartment classification.

All cargo and baggage compartments shall include provisions for safeguarding against fires according to the following classification.

(a) Class A. Cargo and baggage compartments shall be classified as "A" if the presence of a possible fire therein would be easily discernible to a member of the crew while at his station, and if all parts of the compartment are easily accessible in flight. A hand fire extinguisher shall be available for each compartment. (See § 4b.380 (c) for protective breathing requirements.)

(b) Class B. Cargo and baggage compartments shall be classified as "B" if sufficient access is provided while in flight to enable a member of the crew to

It is recommended that signs indicating location of extinguishers have letters at least % inch in height mounted on a contrasting background.

reach effectively all parts of the compartment and its contents with a hand fire extinguisher. Compliance shall be shown with the following:

(1) The design of the compartment shall be such that, when the access provisions are being used, no hazardous quantity of smoke, flames, or extinguishing agent will enter any compartment occupied by the crew or passengers. (See § 4b.380 (c) for protective breathing requirements.)

(2) Each compartment shall be equipped with a separate system of an approved type smoke detector or fire detector to give warning at the pilot or flight engineer station.

(3) Hand fire extinguishers shall be readily available for use in each compartment.

(4) The compartment shall be completely lined with fire-resistant material.

(c) Class C. Cargo and baggage compartments shall be classified as "C" if they do not conform to the prerequisites for the "A" or "B" classifications. Compliance shall be shown with the following.

(1) A separate system of an approved type smoke detector or fire detector to give warning at the pilot or flight engineer station, and

(ii) An approved built-in fire-extinguishing system controlled from the pilot or flight engineer station.

(2) Means shall be provided to exclude hazardous quantities of smoke, flames, or extinguishing agent from entering into any compartment occupied by the crew or passengers.

(3) Ventilation and drafts shall be controlled within each compartment so that the extinguishing agent provided can control any fire which may start within the compartment.

(4) The compartment shall be completely lined with fire-resistant material.

(d) Class D. Cargo and baggage compartments shall be classified as "D" if they are so designed and constructed that a fire occurring therein will be completely confined without endangering the safety of the airplane or the occupants. Compliance shall be shown with the following.

(1) Means shall be provided to exclude hazardous quantities of smoke,