494 [(1) The following minimum number of hand fire extinguishers must be conveniently located in passenger compartments Passenger capacity:
Minimum number of hand fire extinguishers 7 through 30 1 31 through 60 2 61 or more 3
(2) At least one hand fire extinguisher must be conveniently located in the pilot compartment.
(3) A readily accessible hand fire extinguisher must be available for use in each Class A or Class B cargo compartment.
(4) Each hand fire extinguisher must be approved.
(5) The types and quantities of each extinguishing agent used must be appropriate to the kinds of fires likely to occur where used.
(6) Each extinguisher for use in a personnel compartment must be designed to minimize the hazard of toxic gas concentration.
(b) Built-in fire extinguishers. If a built-in fire extinguisher is provided-
(1) The capacity must be adequate for any fire likely to occur in the compartment where used, considering the volume of the compartment and the ventilation rate;
and,]
(2) Each system must be installed so that-
(i) No extinguishing agent likely to enter personnel compartments will be hazardous to the occupants; and
(ii) No discharge of the extinguisher can cause structural damage.
b. Guidance.
(l) Paragraph (a)(1). 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 § 21.301.
(Amendment 25-0)
(2) Paragraph (a)(1). The quantities of extinguishers noted above are the absolute minimum permitted. Virtually all airplanes with 61 or more passengers will require additional extinguishers due to interior amenities (galleys, lavatories etc.) and division of cabins. Refer to AC 20-42C, “Hand Fire Extinguishers for Use in Aircraft,” dated 3/7/84, for guidance on acceptable fire extinguishers. (Amendment 25-54)
(3) Paragraph (a)(5) and (a)(3). For further guidance, refer to National Fire Protection Association (NFPA) 10, "Standards for Portable Fire Extinguishers." (Amendment 25-0)
(4) Paragraph (a)(5). When selecting a hand held fire extinguisher for use in airplanes, consideration should be given to the most appropriate extinguishing agent for the type and location of fires likely to be encountered. At least one extinguisher appropriate for a Class A fire should be provided. Consideration should also be given to the extinguisher 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. Airplane hand held fire extinguishers using extinguisher 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. (Amendment 25-0) NOTE: The toxicity ratings listed by the Underwriters' Laboratories and the halon and freon number for some of the commonly known fire extinguisher chemicals are as follows:
Group Number Halon Number* Freon Number Bromochloromethane 3 1011 --- Bromotrifluoromethane 6 1301 13B1/FE1301 Carbon dioxide 5 --- --- Carbon tetrachloride 3 1040 --- Dibromodifluoromethane 4 1202 12B2 Methyl bromide 2 1001 --- * The halon number is defined as follows: the first number is the number of carbon atoms; the second, fluorine; the third, chlorine; and the fourth, bromine in the extinguisher agent’s chemical formula.
Some older transport category airplanes, due to their type certification bases, are not required to comply with § 25.851. For such airplanes, it is recommended that hand held fire extinguishers employing agents in toxicity Group 4 or higher be installed when renewing or replacing hand held fire extinguishers employing toxic agents. (Amendment 25-0)
(5) Paragraph (a)(5). Types of extinguishers. (Amendment 25-0)
(i) Carbon dioxide extinguishers. Carbon dioxide extinguishers are acceptable when the principal hazard is a Class B or Class C fire. Portable carbon dioxide installations
496 should not exceed five lbs of agent per unit to ensure extinguisher portability and to minimize crew compartment carbon dioxide (CO2) concentrations. (Amendment 25-0)
(ii) 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 CO2 or dry chemical. (Amendment 25-0)
(iii) Vaporizing liquid extinguishers. Vaporizing liquid type fire extinguishers are acceptable when the principal hazard is a Class B or Class C fire. (Amendment 25-0)
(iv) 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. (Amendment 25-0)
(v) Specialized Dry Powder extinguishers for Class D fires. Solid materials in powder or granular form are designed to extinguish Class D combustible metal fires by crusting, smothering, or heat-transferring means. The recommendations of the manufacturer for use of those extinguishers should be followed because of the possible chemical reaction between the burning metal and the extinguishing agent. (Amendment 25-0) NOTE: 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 lbs. These extinguishers have only limited value for the extinguishment of a Class A fire, 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 (TSO)-C19a covers a minimum l-3/8 quart capacity approved water extinguisher. Water extinguishers of the kinds currently on the market are not acceptable for flammable liquid or electrical fires.
Vaporizing liquid extinguisher agents are not normally corrosive to airplane structure and approved units will be satisfactorily protected against freezing to at least -40 °F. Up to the effective date of this guidance, 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 one-tenth that of water. When using dry chemical extinguishers 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 lbs.
(6) Paragraph (a)(5). Class of fires. (Amendment 25-0)
(i) 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. (Amendment 25-0)
(ii) Class B fires. Fires in flammable liquids, greases, etc., where a blanketing effect is essential. (Amendment 25-0)
(iii) Class C fires. Fires in electrical equipment, where the use of a nonconducting extinguishing agent is of first importance. (Amendment 25-0)
(iv) Class D fires. Fires which involve combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium, and require extinguishing agents of the dry powder types. (Amendment 25-0)
(7) Paragraph (a)(5). A fire extinguisher containing at least five (5) lbs of Halon 1211 may be used in lieu of a water extinguisher to combat Class A fires. Alternatively, two (2) fire extinguishers containing at least 2.5 lbs of Halon 1211 each, installed in close proximity to each other, may be substituted for one water fire extinguisher. In locations where one Halon and one water extinguisher are installed and replacement of the water extinguisher is desired, the above guidance will apply, however, the existing Halon extinguisher is not part of the substitution; i.e., three (3) 2.5 pound Halon extinguishers are equivalent to one (1) 2.5 pound Halon and one (1) water extinguisher. The resulting configuration from the replacement of a water fire extinguisher with Halon fire extinguishers must not result in unhealthy, toxic gas concentration. (Amendment 25-0)
604. AMENDMENT 25-74, Effective May 16, 1991.
a. Regulation.
(a) Hand fire extinguishers.
[(1) The following minimum number of hand fire extinguishers must be conveniently located and evenly distributed in passenger compartments:
Passenger Capacity Number of Extinguishers 7 through 30 1 31 through 60 2 61 through 200 3 201 through 300 4 301 through 400 5 401 through 500 6 501 through 600 7 601 through 700 8
(2) At least one hand fire extinguisher must be conveniently located in the pilot compartment.
(3) At least one readily accessible hand fire extinguisher must be available for use in each Class A or Class B cargo or baggage compartment and in each Class E cargo or baggage compartment that is accessible to crewmembers in flight.
(4) At least one hand fire extinguisher must be located in, or readily accessible for use in, each galley located above or below the passenger compartment.
(5) Each hand fire extinguisher must be approved.
(6) At least one of the required fire extinguishers located in the passenger compartment of an airplane with a passenger capacity of at least 31 and not more than 60, and at least two of the fire extinguishers located in the passenger compartment of an airplane with a passenger capacity of 61 or more must contain Halon 1211 (bromochlorodifluromethane CBrC1F2), or equivalent, as the extinguishing agent. The type of extinguishing agent used in any other extinguisher required by the section must be appropriate for the kinds of fires likely to occur where used.
(7) The quantity of extinguishing agent used in each extinguisher required by this section must be appropriate for the kinds of fires likely to occur where used.
(8) Each extinguisher intended for use in a personnel compartment must be designed to minimize the hazard of toxic gas concentration.
(b) Built-in fire extinguishers. If a built-in fire extinguisher is provided-
(1) Each built-in fire extinguishing system must be installed so that-
(i) No extinguishing agent likely to enter personnel compartments will be hazardous to the occupants; and
(ii) No discharge of the extinguisher can cause structural damage.
(2) The capacity of each required built-in extinguishing system must be adequate for any fire likely to occur in the compartment where used, considering the volume of the compartment and the ventilation rate.]
b. Guidance.
(l) 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 § 21.301. (Amendment 25-0)
(2) For further guidance, refer to National Fire Protection Association (NFPA) 10, "Standards for Portable Fire Extinguishers." (Amendment 25-0)
(3) Paragraph (a)(1). The quantities of extinguishers noted above are the absolute minimum permitted. Virtually all airplanes with 61 or more passengers will require additional extinguishers due to interior amenities (galleys, lavatories etc.) and division of cabins. Refer to AC 20-42C, “Hand Fire Extinguishers for Use in Aircraft,” dated 3/7/84, for guidance on acceptable fire extinguishers. (Amendment 25-54)
(4) Paragraph (a)(6). When selecting a hand held fire extinguisher for use in airplanes, consideration should be given to the most appropriate extinguishing agent for the type and location of fires likely to be encountered. At least one extinguisher appropriate for a Class A fire should be provided. Consideration should also be given to the extinguisher 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. Airplane hand held fire extinguishers using extinguisher 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. (Amendment 25-0) NOTE: The toxicity ratings listed by the Underwriters' Laboratories and the halon and freon number for some of the commonly known fire extinguisher chemicals are as follows:
Group Number Halon Number* Freon Number Bromochloromethane 3 1011 --- Bromotrifluoromethane 6 1301 13B1/FE1301 Carbon dioxide 5 --- --- Carbon tetrachloride 3 1040 --- Dibromodifluoromethane 4 1202 12B2 Methyl bromide 2 1001 --- * The halon number is defined as follows: the first number is the number of carbon atoms; the second, fluorine; the third, chlorine; and the fourth, bromine in the extinguisher agent’s chemical formula.
Some older transport category airplanes, due to their type certification bases, are not required to comply with § 25.851. For such airplanes, it is recommended that hand held fire extinguishers employing agents in toxicity Group 4 or higher be installed when renewing or replacing hand held fire extinguishers employing toxic agents. (Amendment 25-0)
(5) Paragraph (a)(6). Types of extinguishers. (Amendment 25-0)
(i) Carbon dioxide extinguishers. Carbon dioxide extinguishers are acceptable when the principal hazard is a Class B or Class C fire. Portable carbon dioxide installations
500 should not exceed five lbs of agent per unit to ensure extinguisher portability and to minimize crew compartment carbon dioxide (CO2) concentrations. (Amendment 25-0)
(ii) 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 CO2 or dry chemical. (Amendment 25-0)
(iii) Vaporizing liquid extinguishers. Vaporizing liquid type fire extinguishers are acceptable when the principal hazard is a Class B or Class C fire. (Amendment 25-0)
(iv) 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. (Amendment 25-0)
(v) Specialized Dry Powder extinguishers for Class D fires. Solid materials in powder or granular form are designed to extinguish Class D combustible metal fires by crusting, smothering, or heat-transferring means. The recommendations of the manufacturer for use of those extinguishers should be followed because of the possible chemical reaction between the burning metal and the extinguishing agent. (Amendment 25-0) NOTE: 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 lbs. These extinguishers have only limited value for the extinguishment of a Class A fire, 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 (TSO)-C19a covers a minimum l-3/8 quart capacity approved water extinguisher. Water extinguishers of the kinds currently on the market are not acceptable for flammable liquid or electrical fires.
Vaporizing liquid extinguisher agents are not normally corrosive to airplane structure and approved units will be satisfactorily protected against freezing to at least -40 °F. Up to the effective date of this guidance, 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 one-tenth that of water. When using dry chemical extinguishers 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 lbs.
(6) Paragraph (a)(7). Class of fires. (Amendment 25-0)
(i) 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. (Amendment 25-0)
(ii) Class B fires. Fires in flammable liquids, greases, etc., where a blanketing effect is essential. (Amendment 25-0)
(iii) Class C fires. Fires in electrical equipment, where the use of a nonconducting extinguishing agent is of first importance. (Amendment 25-0)
(7) Paragraph (a)(7). A fire extinguisher containing at least five (5) lbs of Halon 1211 may be used in lieu of a water extinguisher to combat Class A fires. Alternatively, two (2) fire extinguishers containing at least 2.5 lbs of Halon 1211 each, installed in close proximity to each other, may be substituted for one water fire extinguisher. In locations where one Halon and one water extinguisher are installed and replacement of the water extinguisher is desired, the above guidance will apply, however, the existing Halon extinguisher is not part of the substitution; i.e., three (3) 2.5 pound Halon extinguishers are equivalent to one (1) 2.5 pound Halon and one (1) water extinguisher. The resulting configuration from the replacement of a water fire extinguisher with Halon fire extinguishers must not result in unhealthy, toxic gas concentration. (Amendment 25-0) 605-620. [RESERVED]
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503 SECTION 25.853 COMPARTMENT INTERIORS
621. REGULATION IN EFFECT AT ADOPTION OF PART 25.
a. Regulation.
For each compartment to be used by the crew or passengers
(a) The materials must be at least flash-resistant
(b) The wall and ceiling linings, and the covering of upholstery, floors, and furnishings must be at least flame resistant;
(c) Each compartment where smoking is to be allowed must have self-contained, removable ash trays, and each other compartment must be placarded against smoking;
(d) Each receptacle for towels, paper, or waste must be at least fire resistant and must have means for containing possible fires;
(e) There must be at least one hand fire extinguisher for use by the flight crewmembers; and
(f) There must be at least the following number of hand fire extinguishers conveniently located in passenger compartments:
Passenger capacity:
Minimum number of hand fire extinguishers 7 through 30 1 31 through 60 2 61 or more 3
b. Guidance.
(l) Certification by a material manufacturer/supplier, commonly called “certs,” that a material complies with the flammability requirements of § 25.853 does not satisfy FAA rules.
All flammability tests to demonstrate compliance should be witnessed by the FAA or its representatives. Refer to § 25.1359(d) for guidance relative to wiring. (Amendment 25-0)
(2) Paragraphs (a) and (b). Definitions and procedures for conducting tests were contained in Flight Standards Service Release (FSSR) No. 453. This FSSR was canceled by AC 00-20, “Cancellation of Flight Standards Service Releases,” effective 9/7/66, but the FSSR was never replaced by an AC. The following was derived from FSSR 453, and still should be used for those airplanes whose certification bases included it: (Amendment 25-0)
504 Fire Prevention Test Procedure for Aircraft Materials Fireproof Materials
1. The following test is considered acceptable for demonstrating compliance with §§ 27.861 and 29.861 (CAR §§ 6.384 and 7.384), with respect to those portions which refer to fireproof materials. All structure, controls, rotor mechanism, and other parts essential to a controlled landing should be capable of resisting flame penetration and remain capable of carrying the loads and satisfactorily performing the function for which they are designed when subject to a test flame of 2000 ±50 °F. flame for l5 minutes.
a. Sheet materials should be tested by subjecting the test flame to a test specimen of approximately l0-inches square. The test flame should be applied at the center of the specimen and be of sufficient size to maintain the required temperature over an area approximately five-inches square.
b. Lines, fittings, controls, and other essential components should be enveloped in the test flame on the side that would be exposed in case of a fire when mounted in a manner simulating their actual installation. In the case of fluid fittings, lines or conduits should be connected to both sides of the fittings to simulate actual conditions of heat conduction that would be present during an actual fire in the aircraft. The test should be conducted with the operating fluid in the lines unless the design and function of the system is such as to preclude the presence of the fluid in the lines during an actual fire in the aircraft.
Fire-Resistant Materials
2. The following test is considered acceptable for demonstrating compliance with §§ 25.853, 25.857and (CAR §§ 4b.381, 4b.383, 6.382, 7.38l, and
7.382).
a. If the material is rigid, an eight-inch specimen should be tested. If the material is flexible, the material should be placed in a frame exposing an area of eightinches by eight-inches. If a backing will be used in the airplane, the test specimen should be provided with the same backing.
b. The test specimen should be supported at an angle of 45 degrees to a horizontal surface. The surface that will be exposed, when installed in the aircraft, should face down for the test. The specimen should be exposed to either a Bunsen or a Tirrill burner adjusted for no air intake, giving a yellow-tipped l-l/2-inch flame when resting on a horizontal surface. Suitable precautions should be taken to avoid drafts. The period of flame application should be 30 seconds with one-third of the flame in contact with the material at the center of the specimen.
c. To be acceptable, no penetration of the material should result during application of the test flame or subsequent to its removal, and if the material ignites,
505 the flame should extinguish itself within l5 seconds with no smoldering or glowing visible l0 seconds thereafter.
Flame Resistant Material
3. The following test is considered acceptable for demonstrating compliance with §§ 23.853, 25.853, 25.855and (CAR §§ 3.388(a), 4b.38l, 4b.382,
6.38l, 6.382, and 7.38l).
a. Test specimens. Three specimens, approximately four-inches wide and l4-inches long, should be tested. Each specimen should be clamped in a metal frame so that the two long edges and one end are held securely. The frame should be such that the exposed area of the specimen is at least two-inches wide and l3-inches long, with the free end at least l/2-inch from the end of frame for ignition purposes. In the case of fabrics, the direction of the weave corresponding to the most critical burn rate should be parallel to the l4-inch dimension. A minimum of l0-inches of the specimen should be used for timing purposes and approximately l-l/2-inches should burn before the burning front reaches the timing zone. The specimen should be long enough so that the timing is stopped at least one-inch before the burning front reaches the end of the exposed specimen.
b. Test procedure. The specimens should be supported horizontally and tested in draft-free conditions. The surface that will be exposed when installed in the aircraft, should face down for the test. The specimens should be ignited by a Bunsen or Tirrill burner. To be acceptable, the average burn rate of the three specimens must not exceed four-inches per minute. Alternatively, if the specimens do not support combustion after the ignition flame is applied for l5 seconds, or if the flame extinguishes itself and subsequent burning without a flame does not extend into the undamaged areas, the material is also acceptable. (Federal Specification CCC-T-191b, Method 5906, may also be used for testing materials of this type, but the material should not exceed the above four-inches per minute burn rate.)
Flash-Resistant Materials
4. The following test is considered acceptable for demonstrating compliance with §§ 23.853, 25.853 and CAR §§ 3.388(a), 4b.38l, 6.38l, and 7.38l.
a. Test specimens. Three specimens, approximately 4-inches wide by l4-inches long, should be tested. Each specimen should be clamped in a metal frame so that the two long edges and one end are held securely. The frame should be such that the exposed area of the specimen is at least two-inches wide and l3-inches long, with the free end at least l/2-inch from the end of the frame for ignition purposes. In the case of fabrics, the direction of the weave corresponding to the most critical burn rate should be parallel to the l4-inch dimension. A minimum of l0-inches of the specimen should be used for timing purposes, and approximately l-l/2-inches should