d. Ventilate the Compartment.
(1) When you are reasonably sure the fire is extinguished, ventilate the compartment overboard at the highest possible rate allowed by established crew procedures for your particular aircraft to rid the cabin and flight deck of hazardous gases and smoke. Stay alert when increasing airflow, if the fire is not completely extinguished or smoldering, increasing airflow could promote fire growth.
(2) Small aircraft lack some of the safety advantages available to large transport category aircraft. Large aircraft with small volume occupied spaces (flight decks) have a forced ventilation system, availability of supplemental oxygen (quick donning oxygen masks), and a copilot available. Therefore, operators of small unpressurized aircraft should open a window, if at all possible.
3. How to Prevent Hypoxia in an Unpressurized Aircraft. You can avoid life-threatening hypoxia (low oxygen) hazards that may result from the discharged halocarbon agent displacing air in unpressurized aircraft, by following the descent, ventilation, and supplemental oxygen guidance below. See the report referenced in appendix 3, paragraph 7m of this AC for information on the development of the guidance below.
a. Extinguish Fire and Ventilate Cabin. As mentioned above, make sure the fire is completely extinguished. To rid the cabin and flight deck of hazardous gases and smoke, ventilate all unpressurized aircraft compartments overboard at the highest possible rate allowed by established crew procedures for your particular aircraft. If the fire is not completely extinguished, or a smoldering fire exists, increasing airflow could promote fire growth
b. Descend to Lower Altitudes. Immediately descend at the maximum safe rate to 8,000 ft. or to an altitude that is as low as practicable. Descending dilutes agent concentration, lowers exposure to agent and combustion gases, and increases oxygen concentration. We recommend descending regardless of the amount of agent used, the aircraft size, or ventilation rate. Aircraft with a maximum flying altitude of 12,500 ft. are protected from hypoxia, without the need for supplemental oxygen, by immediately descending as described above.
c. Use Supplemental Oxygen. Use of supplemental oxygen can prevent hypoxia.
However, if a supplemental diluter demand personal oxygen system at CPAs above 12,500 ft., a nasal cannula up to and including 18,000 ft CPA, or an oral-nasal mask between 18,000 ft. and 25,000 ft. CPA are used, the user will not be fully protected from hypoxia. This lack of protection is because the oxygen flow control for these systems is based on pressure altitude, not oxygen partial pressure.
(1) Occupants flying at altitudes above 12,500 ft. should immediately switch their masks or nasal cannula to the maximum flow of oxygen, if so equipped, to get additional protection during the time it would take to exchange the air in the compartment three times.
(2) Fingertip probe oxygen sensors should be used with oxygen systems on unpressurized aircraft with maximum flying altitudes above 12,500 ft. These devices provide user feedback on the effects of hypoxia after halocarbon agent discharge such that the wearer can increase the oxygen flow to their breathing device to compensate for the hypoxia.
(3) Unpressurized aircraft are allowed to use nasal cannula supplementary oxygen systems up to 18,000 ft. altitude. These systems provide no protection to a wearer when he or she breaths through the mouth, which can occur at times of stress.
4. What are the Guidelines on the Selection of Halocarbon Extinguishers?
Extinguisher Performance. Primary consideration in selecting a fire extinguisher should be performance, size, and weight (see appendix 4, paragraph 3 of this AC), hardware configuration, extinguisher throw range (see appendix 4, paragraph 1 of this AC), ease of use for novices, commercial availability of the agent, and environmental issues (ODP and GWP).
Special consideration needs to be made for cold temperature operation, as noted in chapter 3, paragraph 5b of this AC. Agent physical and chemical properties may also be considered.
Toxicity/Human Exposure. As mentioned previously, human exposure to halocarbon agents is a concern and needs to be addressed as noted in paragraph 2b above.
However, it is far less of a concern than the consequences of an unextinguished in-flight fire.
From a hazardous exposure perspective, you may elect to select a halocarbon hand extinguisher using the safe-use W/V guidance (based on perfect mixing) described below for your specific compartment size. Safe-use W/V guidance provides an objective scientific evaluation of the currently approved agents.
(1) The exposure hazard presented by the decomposition products of the agent may be considered when choosing a fire extinguisher for a particular installation.
(2) Safe-use W/V guidance for various air change times, assuming perfect mixing, is presented in appendix 4, paragraph 2 of this AC. The methodology used to develop the safe-use W/Vs of halocarbon agents and their blends was developed in the report referenced in appendix 3, paragraph 7m of this AC. The safe-use W/V guidance is based on the discharge of the largest extinguisher in a compartment at 70° F at the aircraft certificated CPA.
(3) These safe-use W/Vs may be used as general guidance and are based on perfect mixing gas concentration histories. This safe-use W/V guidance is not rigid, as there are many variables that can affect the agent concentration histories. Actual concentrations encountered by occupants may be significantly lower than would be encountered if there was perfect mixing depending on agent stratification, air distribution, air flow, and geometry of a particular aircraft/aircraft compartment and may be adjusted accordingly.
Agent stratification/localization within a compartment, as mentioned in paragraph 4b(3) above, will be addressed in a report to be published at the FAA Technical Center. This report will provide limited examples and the method to properly adjust the safe-use concentrations for those examples. See appendix 4, paragraph 2a(4) 17
(5) For unpressurized aircraft, you should consider safe-use guidance for the highest altitude for which the aircraft is certified.
(6) The cabin is considered and referred to as a compartment. The total charge weight of the largest extinguisher divided by the compartment volume should not exceed the safe-use W/V.
(7) In a pressurized aircraft (6000 to 8,000 ft CPA), the hypoxic hazard is minimal for the safe-use concentrations for the halocarbon agents in this AC. Immediate descent is not necessary. Pressurized aircraft benefit (increased oxygen and decreased agent concentrations) only from descent to altitudes below the CPA. The worst case oxygen equivalent CPA for pressurized aircraft using the safe-use W/V guidance provided in this AC is 10,000 ft at 2 minutes after discharge when 8,000 ft CPA is maintained. However, landing as quickly as possible is always recommended when an onboard fire is suspected.
c. Relative Agent Toxicity. You may want to consider the relative toxicity of extinguishers in Figure 1 below when selecting an extinguisher. Figure 1 shows the normalized toxicities of approved 5B:C extinguishers relative to the NOAEL-based toxicity of a 5B:C Halon 1211 extinguisher. These normalized toxicities are based on exposure to neat (un-decomposed) agent using 3 different measures: NOAEL, Safe Human Concentration and LOAEL.
Figure 1. Relative Toxicity of 5 B:C Halocarbon Extinguishers
1.3
• NOAEL Basis 1 • Safe Human Concentration Toxicity of 5 B:C Extinguishers .9 Basis Relative to Halon 1211 • LOAEL Basis 2
0.0 Halon 1211 Halon 1301 HCFC Blend B HFC-227 ea HFC-236 Agent
d. Minimum Safe Volume. Alternatively, you may consider minimum safe volumes to make your extinguisher selection. In this case, the minimum safe volume of one extinguisher is obtained by dividing that extinguisher's charge weight by the safe-use agent W/V for the appropriate altitude and ventilation (See appendix 4, paragraph 3 of this AC).
5. How to Safely Use Halocarbon Extinguishers in Accessible Cargo Compartments.
a. Unsafe Concentrations of Extinguishing Agent. 14 CFR § 25.857 and § 29.855(d) require aircratt to be designed to prevent the harmful accumulation of smoke, flame, extinguishing agent and noxious gases from entering occupied areas. Airplane Flight Manual (AFM) fire fighting procedures should state that the crew member should close the Class B cargo compartment door after extinguishing a fire.
When to Use Portable Protective Breathing Equipment (PBE). Portable PBE should be worn before entering the cargo compartment and attempting to extinguish a fire, as outlined in 14 CFR § 25.1439. Note that AFM and/or Crew Operations Manual are required to have the appropriate procedure including calling out the use of portable PBE and other emergency equipment necessary to fight a fire.
Compartments Under 200 Cubic Feet. Halon replacement extinguishers should have a minimum fire rating classification of U.S. - UL 2A:10B:C for accessible Class B cargo compartments, combination passenger/cargo (combi) and cargo airplane/rotorcraft. The fire threat for accessible cargo compartments is primarily from Class A fires. Usually, one extinguisher with a U.S. - UL 2A: 10B:C rating is sufficient to fight most fires likely to occur.
(1) Multiple hand-held fire extinguishers may be shared to comply with the cabin and accessible Class B cargo compartment regulations, if they are located where a person fighting a fire in the compartment could quickly retrieve them and continue fighting the fire with minimal delay between the discharges. It must be demonstrated that the extinguishers, as installed, can extinguish 2A and 10B:C rated fires. The combined rating is to be determined by performing the UL 711 fire tests by discharging the extinguishers with a delay between the end of each extinguisher's discharge and the start of the discharge of the next extinguisher based on the location of each extinguisher and an assessment of factors such as:
(a) The manpower available to fight the fire. If two trained crew members are available to fight the fire, it may be possible to avoid a delay between discharges of the extinguishers.
(b) The time to recognize the completion of the discharge, to walk to the location of the next bottle, remove it from it's mounting bracket, pull the pin, return to the cargo compartment, position the extinguisher to continue to fight the fire and initiate discharge.
(2) The rating is based on UL 711 performance tests, not agent weight, as the agent weight is not sufficient to predict performance. Nozzle design, super pressurization and other factors affect performance. The UL fire tests can be preformed by the applicant or an approved test laboratory such as UL.
Note: The recommended extinguisher rating of 2A: 10B:C is lower than the 2A:40B:C rating in AC 20-42C. This is because the fire threat for accessible cargo compartments is primarily from Class A fires. The prior guidance in AC 20-42C was based on the need for at least a 2A rating for class A fires using a Halon 1211 extinguisher to extinguish a fire. Halon 1211 extinguishers that have a class A rating of 2A also have a 40B:C rating. It has been determined that a 10B:C rating is more then adequate for the type and size of class B and C fires likely to occur in a Class B cargo compartment.
Compartments Over 200 Cubic Feet. Accessible cargo compartments of 200 ft3 and larger, in combination passenger/cargo and cargo aircraft/rotorcraft, should comply with the requirements of the FAA Airworthiness Directive (AD) 93-07-15. This AD specifies acceptable forms of fire protection equipment and operational procedures. The options provided include converting the compartment to meet the requirements of a Class C cargo compartment, use of hand-held fire extinguishers, or the use of fire containment containers or covers, fire extinguishing systems and smoke or fire detectors.
(1) If you elect to use hand fire extinguishers provide the following:
(a) A minimum of three U.S. - UL listed Halon 1211 or its equivalent 2A: 10B:C hand held fire extinguishers (equivalent to the AD's requirement of 48 Ibs. of Halon 1211) readily available for use in the cargo compartment.
(b) At least two U.S. - UL 2A (2-1/2 gallon) listed water portable fire extinguishers, usually TSO C19 or its equivalent, adjacent to the cargo compartment entrance for use in the compartment.
(c) Protective garments stored adjacent to the cargo compartment entrance.
(d) Portable PBE with a minimum of 15 minutes of protective breathing, per 14 CFR § 25.1439(b)(5). This portable PBE should be TSO C116 approved or equivalent, and be stored adjacent to the cargo compartment entrance.
(2) If no extinguisher is available that meets the safe-use criteria for the aircraft/rotorcraft cabin, consider converting that cargo compartment to a class C compartment with a built-in fire suppression system, or any other technology that would provide effective fire protection. Restrict personnel from entering the cargo compartment for the duration of the flight.
How to Inspect and Maintain the Hand Fire Extinguisher for Continued Safe-Use.
Maintain and inspect hand fire extinguishers in accordance with the manufacturer's nameplate instructions. Follow the maintenance procedures, inspections and testing specified in the applicable NFPA and U.S. - UL standards.
a. Non-refillable, disposable fire extinguishers may have plastic discharge heads installed. Locate this type of fire extinguisher in a safe area to assure there will be no damage to the plastic discharge heads.
b. Non-refillable, disposable fire extinguishers are exempt from periodic hydrostatic testing. However, replace these extinguishers with a serviceable unit upon reaching:
(1) The service life where hydrostatic testing would normally be required for a similar extinguisher, or
(2) The service life guidelines established by the manufacturer if sooner.
c. Recommended procedures for the inspection, hydrostatic test and life limits of pressure cylinders are outlined in:
(1) Specification of cylinders is in 49 CFR, part 178, subpart C.
(2) Inspection and maintenance of cylinders is in 49 CFR, part 180, subpart B.
(3) Fire extinguishers are addressed in 49 CFR § 173.309 and in 29 CFR § 1910.157.
d. Manufacturers of fire extinguishers containing halon replacement agents approved for use on FAA certified aircraft should take immediate action through the appropriate channel(s) to have their retest requirements included in the aforementioned regulatory guidelines.
Chapter 5. Locating and Mounting Hand Fire Extinguishers Where to Locate and Mount Hand Fire Extinguishers in Passenger Compartments.
Install fire extinguishers in passenger compartments according to 14 CFR §§ 23.851, 25.851, and
29.853 and the following criteria:
a. Locate hand fire extinguishers adjacent to hazardous areas (for example, galleys, accessible baggage or cargo compartments, electrical equipment racks, etc.) to be protected.
b. If there are no defined hazardous areas, locate the hand fire extinguishers as follows:
() When one extinguisher is used, locate it at the flight attendant's station.
(2) When no flight attendant is required, locate the extinguisher at the passenger entrance door.
(3) When two or more extinguishers are used, locate one at each end of the passenger compartment and space the remainder uniformly within the cabin area.
C. Mount hand fire extinguishers for ready accessibility. It they are not visible in their mounted position, use a placard to indicate their location.
(1) Aircraft structure and mounting brackets are required to withstand the applicable inertia forces required in 14 CFR §§ 23.561, 25.561, 27.561, and 29.561, with the hand fire extinguisher installed. Replacement of halon extinguishers with halocarbon extinguishers will require an evaluation of the mounting system strength. The mounting structure may need to be strengthened. Halocarbon clean agent extinguishers of the same listing can be 2-3 times the weight of the halon extinguishers they are replacing.
(2) For large transport category aircraft, installation of an extinguisher should include vertical reach combined with horizontal (offset) reach to ensure ease of retrieval from overhead compartments. The vertical reach should not exceed 74.5 in. (189.23 cm) combined with an offset reach of 7.87 in. (20cm) to permit a 5 percentile female, 60.5 in. (153.67 cm.) tall to quickly access the extinguisher. Consideration should be allowed for assist steps (or seats) or other factors.
(3) Add the weight of the hand fire extinguisher and its mounting bracket to the aircraft empty weight and a compute a new empty weight center of gravity.
Consider the type of fire hazard (Class A, B, CorD) expected to be encountered when you select a hand fire extinguisher. If extinguishers intended for different classes of fire are grouped together, consider marking their intended use conspicuously via a placard or other means (near the extinguisher) to aid in the choice of the proper extinguisher at the time of the fire.
2. How to Locate and Mount Hand Fire Extinguishers in Flight Deck Compartments.
Consider using the following criteria if you install a fire extinguisher in the flight deck compartment:
a. Each hand fire extinguisher should be conveniently located, readily accessible, and it's location obvious.
b. Hand fire extinguishers should be mounted for easy release and removal. For aircraft designed for single pilot operation, the hand fire extinguisher should be located for release and removal by the pilot in the seated position.
(1) Secure the extinguisher(s) in mounting brackets) such that it requires a deliberate action to release the extinguisher from its primary restraint for removal from its mounting. Design the mounting bracket so that upon release from their primary restraint, the extinguisher remains in position until removed from its mounting by the user.
(2) Aircraft structure and extinguisher mounting brackets must be capable of withstanding the inertia forces specified in paragraph 1c above.
c. Fire extinguishers for the flight deck compartment should be able to extinguish Class B and C fires.
3. How to Locate and Mount Hand Fire Extinguishers in Small Single Engine and Multiengine Aircraft.
a. Locate hand fire extinguishers so that they are easily accessible to the flight crew and the passengers.
b. Do not allow hand fire extinguishers to lie loose on shelves, seat back pockets or seats. Properly mount the hand fire extinguisher to the airframe structure.
c. Aircraft structure and extinguisher mounting brackets should be capable of withstanding the inertia forces specified in paragraph 1c above.
4. How Many Hand Extinguishers Must I Install?
a. Transport Category Airplanes. 14 CFR §§ 25.851(a) and 121.309(c) requires a minimum number of hand extinguishers to be installed on transport category airplanes.
(1) The minimum number of hand fire extinguishers that must be conveniently located and evenly distributed in passenger compartments are as shown in Figure 2 below.
Figure 2. Minimum Number of Hand Fire Extinguishers Required for Transport Category Aircraft Passenger Compartments Passenger No. of Capacity Extinguishers 7 through 30 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, per 14 CFR § 25.851(a)(3).
(4) 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, or equivalent, as the extinguishing agent.
(5) 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.
b. Transport Category Rotorcraft. Title 14 CFR § 29.853 requires a minimum number of hand extinguishers to be installed in passenger compartments:
(1) See Figure 3 below for the minimum number of hand fire extinguishers that must be conveniently located in passenger compartments.
Figure 3. Minimum Number of Hand Fire Extinguishers Required for Transport Category Rotorcraft Passenger Compartments Passenger No. of Capacity Extinguishers 7 through 30 31 through 60 2 61 or more 3
(2) There must be a hand fire extinguisher for the flight crewmembers.
(3) There are no requirements for extinguishing systems or hand extinguishers for accessible cargo or baggage compartments in transport category rotorcraft. Use the hand extinguisher guidance provided in chapter 4, paragraph 6 of this AC for these compartments.
c. Small Airplanes. Title 14 CFR §§ 23.851 and 91.513(c) requires a minimum number of hand extinguishers to be installed on small part 23 airplanes.
(1) At least one hand fire extinguisher must be located within easy access of the seated pilot.
(2) At least one hand fire extinguisher must be in the passenger compartment of an airplane that accommodates more than six passengers. The extinguisher must minimize the hazard of toxic gas concentration.
Appendix 1 Appendix 1. List of Acronyms 14 CFR Title 14, Code of Federal Regulations Advisory Circular ACO Aircraft Certification Office AD Airworthiness Directive AFM Airplane Flight Manual American Society of Testing and Materials Civil Aviation Authority Code of Federal Regulations Cabin Pressure Altitude Department of Transportation U.S. Environmental Protection Agency FAA Federal Aviation Administration FAATC FAA Technical Center FC Fluorocarbon FCOM Flight Crew Operations Manual FIC Fluoroiodocarbon FK Fluoroketone FM Factory Mutual Research Corp.
HCFC Hydrochlorofluorocarbon HF Hydrogen Flouride HFC Hydrotluorocarbon ICA Instructions for Continued Airworthiness ISO International Organization for Standardization LOAEL Lowest Observable Adverse Effect Level MF Multiplication Factor MPS Minimum Performance Standard No Observable Adverse Effect Level National Fire Protection Association Perfluorocarbon Protective Breathing Equipment Physiologically Based Pharmacokinetic Personal Digital Assistant Portable Electronic Device Regulatory Guidance Library Radio Technical Corporation of America Society of Automotive Engineers Significant New Alternatives Policy Air Change Time Technical Standard Order Underwriters Laboratories United States Coast Guard W/V Weight per Unit Volume (W/V) Ratio %V/V Volume Percent A1-1
Appendix 2 Appendix 2. Definitions and Terms The following definitions and terms apply when following the procedures outlined in this AC:
1. Air Change Time. t. is the time in minutes, it takes for the inflow of fresh air into a compartment, with a volume equivalent to the volume of the compartment.
2. Cabin Pressure Altitude is specified for transport aircraft by regulation to be the air pressure in the cabin or compartment of a commercial airliner and it must not be lower than that found at an altitude of 8,000 ft (2,438 m) under normal operating conditions, per § 25.841(a) Cargo Aircraft are aircraft configured solely to carry cargo and no personnel other than the flight crew and any additional crew required for the care of the cargo.
4. Clean Agent is electrically nonconducting, volatile or gaseous fire extinguishant that does not leave a residue upon evaporation. The word agent as used in this circular means clean agent unless otherwise indicated.
5. Combi Aircraft are designed/configured to transport both passengers and cargo on the same level within the fuselage.
6. Compartment is an enclosed space on an aircraft. Examples of compartments are a flight deck, a crew rest, and a cabin. The aircraft cabin is considered one compartment.
7. Dry Chemical is a mixture of finely divided solid particles, usually sodium bicarbonate, potassium bicarbonate, or ammonium phosphate-based with added particulate material supplemented by special treatment to provide resistance to packing, and moisture absorption (caking) and to promote proper flow characteristics.
Dry Powder is solid materials in powder granular form designed to extinguish class D combustible metal fires by crusting, smothering, or heat transferring means.
9. Flight Crew are responsible for the operation and management of the aircraft flight controls, engines, and systems, including, but not limited to, pilot in command (captain), first officer (copilot), second officer (flight engineer).
10. Flight Deck is the compartment of the aircraft arranged for use by the flight crew in operating the aircraft.
11. Galley is the area of the aircraft for storing, refrigerating, heating and dispensing of food and beverages.
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