t ‘) w 

U.S. DepaftlWflt 

of Transportation 

Federal Aviation 

Administration 

Advisory 

Circular 

Subject: HAND FIRE MTINGUISHERS FOR Date: 3/7/84 AC No: 20-42C 

USE IN AIRCRAFT Initialed by: AWS-3 4 0 Change: 

1. PURF0SE. This advisory circular (AC) provides methods acceptable to the 

Administrator for showing compliance with the hand fire extinguisher provisions 

in Parts 25, 29, 91, 121, 125, 127, and 135 of the Federal Aviation Regulations 

(FAR), and provides updated general information. In addition, the information 

in this AC is considered acceptable for use by the cwners/operators of small 

aircraft. 

2. Fmus. Changes made to same of the FAR requirements for hand fire 

extishers used in aircraft are of utmost mncem to both aircraft cwners/ 

operators and aviation reintenance agencies. Recent advancements in fire 

fighting technology and the proliferation of approved hand-held extinguisher 

models containing Halon 1211, l.301, and combinations of the two, require that 

this AC be updated. 

3. CANCELLATION. AC 20-42R, Hand Fire Extinguishers for Use in 

dated August 25, 1982, is canceled. 

Aircraft, 

4. RELATED FAR SECl’IONS AND CODE OF FEDERAL RFXXIATICNS (CFR). 

a. 

b. 

C. 

d. 

e. 

f. 

g* 

h. 

1. 

jk. 

FAR 21.305. 

FAR 23.561. I 

FAR 25.561; 25.851. 

FAR 27.561. 

FAR 29.561; 29.851; 29.853(e) and (f). 

FAR 91.193(c). 

FAR 121.309(c). 

FAR 125.119(b) and (cl. 

FAR 127.107(c). 

FAR 135.155. 

Title 46 and 49 of the CFR. 
AC 20-42C 3/7/84 

5. DEFINITIONS. 

a. Halon. A short derivation for "halogcnated hydrocarbon" whose chemical 

StructureTidentified as a four digit number representing, respectively, the 

number of carbon, fluorine, chlorine , and bromine atoms present in one molecule. 

Halon fire extinguishing agents approved for use include Halon 1211, Halon 

l301, and A combination of the two (Halon 1211/l301). Both are liquified gases 

and typified as "clean agents," leaving no agent residue after discharge. 

Halons extinguish fire ty chemically interrupting the axnbustion chain reaction 

rather than & physically .mthering. 

b. Halon 1211. The chemical name is hra--ochlorodifluormthane, 

CBrClF2. Halon 1211 is a rmltipurpose, Class A, R, C rated agent effective 

against flaxrmahle liquid fires. he to its relatively high boiling point 

(-4"C/+2S°F), Halon 1211 discharges as an 85 percent liquid stream offering 

long agent throw range. 

C. Halon l.301. The chemical M is branotrifluormthane, CBrF3. 

Halon I301 is recognized as an agent having Class A, B, C capability in total 

florxling systers; however, Halcn I301 offers limited Class A capability when 

used in portable fire extinguishers. 

d. Hand Fire Extinguisher (Aircraft Hand Fire Extinguisher/Portable Fire 

Extinguisher). An approved, portable fire extinguisher as outlined in 

paragraph 6 of this AC, tiich mn be used b aircraft occupants to conbat 

accessible, incipient, on-toard fires. 

6. APPROVED HAND FIRE FXTINGUISHERS. Hand fire ext.inguishers are acceptable 

under FAR Sections 25.851(a)(l), 29.851(a)(l), 121.309(c), 127.107(c) and 

US.155 if they have heen approved in accordanoe with FAR 21, .Section 21.305. 

In accordance with !%ction 21.305(d) of the FAR the Federal Aviation 

Administration (FAA) accepts hand fire extinquishars approved b Underwriters' 

Laboratories, Inc., Factory Mutual %search Corp., or approved by the 

U.S. Coast Guard under Title 46 of the CFR for use in aircraft. Although 

Parts 91 and 125 do not require FAA approval of hand fire extinguishers, the 

information in this AC is considered acceptable for use by Parts 91 and 125 

operators. Operators of nontransport category aircraft should become fhiliar 

with the information in this AC and the precautions listed in paragraph 8f for 

the different types of fire extinguishers. In addition, the recormzndat ions of 

the extinguisher mnufacturer should be considered. 

7. DISCUSSIoN. 

a. 'I@e.s of Fires. To properly select an appropriate extinguisher for use 

in an aircraft, it is recomrended that consideration he given to the following 

classes of fires (as defined in the National Fire Protection Association (NFPA) 

Standard 10) thc7t are likely to occur: 

(1) Class A. Fires in ordinary combustible mterials, such as wood, 

cloth, paper, rubber, and plastics for which the quenching anti cooling effects 

of quantities of water, or of solutions containinq a large percentage of water, 

are of prim importance. 

2 Pear 5 
3/7/M AC 20-42C 

(2) Class B. Fires in flmble liquids, oils, greases, tars, oil 

base paints, lacquers , and flamnable gases for which extinguishing agents 

having a blanket effect are essential. 

(3) Class C. Fires which involve energized electrical equipnt and 

where the electrical nonconductivity of the extinguishing rredia is of 

importance. 

(4) Class D. Fires which involve ccmbustible mtals, such as 

magnesium, titanium, zirconium, sodium, lithium, and potassium, and require 

extinguishing agents of the dry powder types. The reco;rrFlendations of the 

manufacturer for use of those extinguishers should he followed because of the 

possible chemical reaction'between the turning netal and the extinguishing 

agent. 

h. Extinquishing Fgents Appropriate for 'Qpes of Fires. The following 

extinguishing agents are recomnded, as appropriate, for use on the types of 

fires specified below and as defined in paragraph 7a of this AC: 

(1) Carbon Dioxide - Class R or C. 

(2) Water - Class A. 

(3) Dry Chemicals - Class A, B, or C. 

(4) Halogenated Hydrocarbons - Class A, B, or C. 

(5) Specialized Dry Pmder - Class D. 

N0l-T : Only "all purpose" or A, B, C dry chemical pcwder extinguishers 

containing ronoarrno nium phosphate have a UL Class A, B, C rating: 

all other powders have a Class B, C rating only. 

C. Numeral Ratings. Nwerals are used with the identifying letters for 

extinguishers labeled for Class A and Class B fires. The "numeral" indicates 

the relative extinguishing effectiveness of the device on a given size fire 

which is dependent cn the agent, the capacity of the device, discharge times, 

and design features. For exalrple, an extinguisher rated as 4A should extinguish 

about twice as rmch Class A fire as a 2A rated extinguisher. A 2 i/2-gallon 

water extinguisher is rated 2A. Cn an extinguisher rated for Class R fires, 

the numeral rating precedes the letter "B". Nmral ratings are not used for 

extinguishers labeled for Class C or D fires. Extinguishers that are effective 

on m3re than one class of fires have mltiple "nweral-letter" and "letter" 

classifications and ratings: for example, 5B:C. 

d. Haloqenated Agents. For hand fire extinguishers employing halogenated 

aqents, only Halon 1211, l.301, or mixtures of the two should be used. The 

following Military Specifications cover the requirements for halogenatsd 

agents: 

(1) Halon 1211 should rreet the requirements of Military Specification 

MIL-B-38741. 

Par 7 3 
AC ZO-42C 3/7/u+ 

(2) Halon l301 should neet the reguirertt?nts of Military Specification 

MIL-M-12218C. 

e. Halon 1211 Extinguishers. 

(1) For occupied spaces cc1 aircraft, Halon 1211 extinguishers should 

not be less than 2 l/2 pounds (1.2 kg) capacity. These extinguishers should 

have a minimum 5R:C rating; not less than 8 seconds effective discharge tire; 

not less than a lo-foot (3 m) range: and nay ba equipped with a discharge hose. 

(2) For occupied spaces cn small aircraft cnly, with a maxim 

certificated occupant capacity of cne to four persons, including the pilot, a 

Halon 1211 extinguisher may be used as an @ion in place of the recczmended 

Halon l301 extinguisher. 

(3) For accessible cargo corrpartments of oombination passenger/cargo 

aircraft and cargo aircraft, Halon 1211 extinguishers should not ba less than 

l3 pounds (5.9 kg) capacity, and have a minimm 2A, 4OR:C rating. 

(4) If Halon 1211 extinguishers are installed in a nonentilated, 

passenger-occupied corrpartnent , and the cclmpartn-ent cannot be vented, and the 

occupants cannot leave if the extinguishers are discharged, then the total 

Halon 1211 agent available fran all the extinguishers should not be capable of 

producing a concentration greater than2 percent by volume at 120°F (49°C) in 

the ccifpartrent. For ccqartments where egress is possible within one minute, 

the maximum design concentration can be 4 pera?nt & volurre. For ventilated 

canpartmnts the guidelines in paragraph 8f(S) of this AC can be used. 

(5) Halon 1211 extinguishers have their greatest effectiveness cn 

Class R and C fires. Extinguishers with 9 pounds (4 kg) or greater capacity 

are also rated for Class A fires. Extinguishers with a capacity of less than 

9 pounds (4 kg), although not rated for use cn Class A fires, have been shown 

to be effective in extinguishing surface Class A fires. Detailed information 

on Halon 1211 agent characteristics , concentration reguirements, health 

hazards, and extinguishing limitations may be found in NFPA Standard 12R, Halon 

1211 Fire Extinguishing Systems. 

(6) Halon 1211 extinguishers of less than 9 pounds (4 kg) capacity are 

not always furnished with a discharge hose. Hmever, for access to underseat, 

overhead, and other difficult to reach locations, consideration should be . 

given to using extirquishers equipped with a discharge hose of a minirum length 

of 12 inches (304 ~wJ). An extinguisher with a discharge hose is ITXT? likely to 

result in the extinguisher being properly held in an upright position during 

US. 

f. Halon I.301 Extinguishers. 

(1) For occupied spaces on aircraft, Halon l301 extinguishers should 

have a minimum 2R:C rating, and should have an effective discharge tire of not 

less than 8 seconds. 

4 Par 7 
317184 AC 20-42C 

(2) If Halon 1301 extinguishers are installed in a nonventilated, 

passenger-occupied ccmpartmant, and the martment cannot he vented, and the 

occupants cannot lea= if the extinguishers are discharged, then the total 

Halon YOl agent available from all the extinguishers should not be capable of 

producing a concentration greater than 5 percent & volume at 120°F f49OC) in 

the ccmpartmnt. For martmants where egress is possible within one minute, 

the reximum design concentration can be 10 percent by volume. For ventilated 

compartrrents the guidelines in paragraph 8f(5) of this AC can be used. 

(3) Halon 1301 extinguishers are effective cn Class R and C fires. 

Halon I301 extinguishers are not rated for Class A fires at this time. 

Detailed information on Halon l301 agent characteristics, concentration 

requirerents, health hazards, and extinguishing limitations may be found in 

NFPA Standard 12A, Halon l301 Fire Extinguishing Systems. 

(4) For occupied spaces cn small aircraft where neat state 

(undecomposed) halon mnoantrations will be approaching allowable limits, 

Halon l301 is the halogenated agent of choice for the following reasons: 

(a) Both Halon 1211 and Halon 1301 decorqose when exposed to 

flame producing toxic products of decorposition. Halon 1211 produces soma 

decomposition products which are not produced by Halon l301 and is, therefore, 

also considered 1~0re toxic in the decomposed state. 

(h) Health and safety advantages associated with similar volume 

occupied spaces on larger aircraft (flight dacks) do not usually exist for the 

smaller aircraft. These advantages are a forced ventilation system, availability of oxygen masks, and availability of a second individual capable of 

flying the aircraft. 

g* Location and Mounting of Hand Fire Extinguishers in Passenger 

Compartments. It is acceptable to install fire extinguishers in passenger 

ccmpartmants according to the following criteria: 

(1) In general, locate hand fire extinguishers adjacent to the 

hazardous area (i.e., galleys, accessible baggage or cargo coqartments, 

electical equipment racks, etc.) they are intended to protect. 

(2) If no clearly defined hazardous area exists, locate the hand fire 

extinguishers as follows: 

(a) When cne extinguisher is used, locate it at the flight 

attendant's station or, where no flight attendant is required, locate the 

extinguisher at the passenger entrance door. 

(b) When two or r-ore extinguishers are used, locate cne at each 

end of the passenger compartwnt and space the remainder uniformly within the 

cabin area. 

(3) Mount hand fire extinguishers so that they are readily available. 

If they are not visible in their rounted position, a placard (with letters at 

least 3/S-inch high) may be used to indicate their location. 

Par 7 5 
AC 20-42C 317184 

(a) Due to the weight of hand fire extinguishers, the aircraft 

structure and extinguisher rounting brackets should be capable of withstanding 

the inertia foroes required in Sections 23.561, 25.561, 27.561, and 29.561 of 

the Federal Aviation Regulations, with the hand fire extinguisher installed. 

(b) The weiaht of the hand fire extinguisher and its lslountinq 

bracket should be added to the 

center of gravity computed. 

aircraft empty weight and a .nzw empty weight 

(4) Fire extinguisher 

of fire hazard (Class A, R, C, 

intended for different classes 

should be marked conspicuously 

at the time of the fire. 

selection should be made with regard to the type 

or D) to he encountered. If extinguishers 

of fire are grouped together, their intended use 

to aid in the choice of the proper extinguisher 

h. Location and Mounting of Hand Fire Extinquishers in .Small Single Enqine 

and Multiengine Aircraft. 

(1) Iccate hand fire extinguishers so that they are easily accessible 

to the flightcrew and the passengers. 

(2) Hand fire extinguishers should not be allowed to lie loose cn 

shelves or seats. Fire extinguishers and rountinq brackets should be properly 

mounted to the airframe structure capable of withstanding the inertia forces 

required by the FAR .Sections listed in paragraph 7g(3 )(a) of this AC. 

8. GENERAL INFORMATION. 

a. Extinguishing Agent Toxicity. Since the toxicity groupings of various 

fire extinguishing agents are no longer considered valid comparisions, the 

Underwriters' Laboratories, Inc., classification of comparative life hazards of 

various chemicals has been eliminated. 

b. Corrosion by Extinguishing Agents. Carbon dioxide is not corrosive 

and will have no damaging effect other than cold shock effect cn oaramic 

electronic components. Water itself is not corrosive, but may ba rendered 

corrosive by the addition of antifreeze solutions. Various dry chemical agents 

are corrosive to rrnst sensitive electronic components and instruments. 

Winterized Hand Fire Extinquishers. 

wintziized down to a -65'F (-54°C). 

Hand fire extinguishers may be 

Extinguishers containing plain water only 

can ba protected to temperatures as low as -40°F (-4OY) by the addition of an 

antifreeze stipulated on the extinguisher nameplate. ,sOme extinguishers that 

use nitrogen as an expellent gas rather than carbon dioxide are approved or 

listed for temperatures as low as -65OF (-54OC). 

d. Factory Sealed ("Disposable 'I&e") Fire Extinguishers. Disposable type 

fire extinguishers should tz maintained and inspected in accordance with the 

nameplate instructions. 

(1) Nonrefillable disposable fire extinguishers have plastic discharge 

heads installed. Care should be exercised in the location of this type of fire 

extinguisher to eliminate damage. 

6 Par 7 
AC 20-42C 

(2) Nonrefillable disposable fire extinguishers are exempt from the 

periodic hydrostatic test requirements. 

(3) These type of fire extinguishers are nomlly charged with a dry 

chemical extinguishing agent and have the sama fogging effect and chemical 

reaction as standard dry chemicai fire extinguishers. 

e. Advantaqes of IJsing Haloqenated Agent Extinquishers. 

(11 Halon 1211, Halon l301, or 1211/l301 is similar to CO2 in that 

it is suitable for use in cold weather and leaves no residue. 

(2) Halon 1211, Halon UOl, or 1211/1301 is three timzs as effective 

as a Co2 extinguisher having equal weight of agent. 

(3) Halon 1211 is a liquefied gas which leaves the nozzle in a stream 

that is about 85 percent liquid and 15 percent gas. This gives the agent a 

range of g-to-15 feet and offers significant advantages in fighting fires in 

large aircraft cabins. Halon l301 is gaseous upon discharge and has A more 

limited threw range. Mixtures of Halon 1211 and Halon l301 have discharge 

characteristics dependent on the component weight ratio. 

(4) Hecause it is a gas, at normal tevratures, Halon 1211, 

Halon l301, or 1211/UOl leaves no chemical residue behind to contaminate or 

corrcde aircraft parts or surfaces. 

(5) Other advantages of Halon 1211, Halon l301, or 1211/YOl are 

lawer cold shock characteristics on electronic equipment, no degradation of 

visual acuity, and lower pressure. 

f. Precautions. 

(1) Dry chemical extinguishing agents when discharged in crew 

canpartmants or confined areas may cause serious impairment to visibility. 

In addition, they may cause tewrary breathing difficulty during and 

imdiately after discharge. 

(2) Tests indicate that human exposure to high levels of Halon vapors 

may result in dizziness, *aired coordination, and reduced rental sharpness. 

Exposure to natural agents is generally of less concern than is exposure to the 

decomposition products. Exposure to undecornposed halcxgenated agents may 

produce varied central nervous system effects depending upon exposure 

concentration and tima. Halogenated agents will also decompose into more toxic 

products when subjected to flame or hot surfaces at approximately 900°F 

(482'C). HOwever, unnecessary exposure of personnel to either the natural 

agent or to the decovsition products should he avoided. The decomposition 

products of the Halon have a characteristic sharp, acrid odor, and an eye 

irritating effect, even in concentrations of only a few parts per million. 

Generally, decomposition products from the fire itself, especially carbon 

monoxide, smoke, haat, and oxygen depletion , create a greater hazard than the 

thermal decomposition products of Halon. See NFPA Standard 12A, Halon I301 

Fire Extinguishing Systems, and NFPA Standard 12R, Halon 1211 Fire 

Extinguishing System, for m3re detailed information. 

Par 8 7 
AC 20-42C 3/7/84 

NOTE: Never discharge Halon 1211 on Class D (humirq metal) fires. 

(3 1 Under ncnventilated conditions, Underwriters' Laboratories, Inc., 

recmnds that the mximlm conoentration of Halon 1211 not exceed 2 percent in 

an enclosure, and the maxirum concentration of Halon YOl not exceed 5 percent. 

For sea-level altitude and a temperature of 120°F (48.9"C), the corrpartrrent 

volurrre in cubic feet that will result in these concentrations, for a given 

weight of agent, is found & multiplying the agent charge weight in pounds by 

124.7 in the case of Halon 1211, and hy 52.6 in the case of UOl. 

(4) Carton dioxide extinguishes fire by reducing the concentration of 

oxygen and/or the gaseous phase of the fuel in the air to the point where 

combustion stops. Carbon dioxide will not support life when used in sufficient 

concentration to extinguish a fire , and it should not be used in habitated, 

nonventilated aircraft compartments. Ixle to oxygen deficiency, prolonged 

occupancy can produce unconsciousness and death at higher concentrations. A 

concentration of 9 precent is about all most persons can withstand without 

losing consciousness within a few minutes. At conozntrations above 9 percent, 

occupants would quickly lose consciousness. At concentrations of about 20 

peroant, death would follow in about 20-to-30 minutes, unless the victim was 

removed to a source of fresh air. (I&f. NFPA Standard 12, Appendix Al. 

Carbon dioxide must be at a 34 percent concentration to effectively extinguish 

a gasoline fire. 

(5) For ventilated compartments, the ncmographs shown in Appendix 1, 

Figures 1, 2, ati 3 of this AC can be used to find safe extinguisher sizes when 

canpartment velure and ventilation rates are knmn. The ncmographs are based 

on allowable doses of 4 percent minutes, 10 percent minutes, and 25 percent 

minutes for Halon 1211, Halon UOl, and CO2 respectively. Because of the 

effect of CO2 on human respiration rate, the allowable CO2 would have 

to be reduced & a factor of six from the amount allowed hy the CO2 

ncmograph to reduce changes in human respiration rates. The Halon 1211 and 

1301 nomographs are entirely consistent with recognized statiards. If 

extinguishers larger than those indicated & the selected na-rographs are 

installed, use of protective breathing equipment should be considered. These 

ncn-cgraphs are essentially for aircraft for which rates are controllable and 

knmn. To use a selected narqraph, extend a straight line across the three 

vertical scales, crossing the air change and compartment volurre scales at the 

figures appropriate for the aircraft, a nd crossing the agent scale at weight 

appropriate for that air change time and volume. 

(6) Extinguishers antaining a given weight of a mixture of Halon 1211 

and l301 should be treated as if the total agent weight were completely 

Halon 1211 in terms of quantitative guidelines cited in paragraphs 7e(4), 7e(5), 

8f(3), and 8f(5) of this AC. For all aircraft applications in habitated 

compartments, Halon 1211, 1301, and mixtures of the two should ba agents of 

choice as mmpared to C02. 

Par 8 
3/7/N AC 20-42C 

g* Helpful Hints. 

(1) nest results in fire fighting are generally obtained by attacking 

the base of the fire at the near edge of the fire and progressing toward the 

back of the fire by moving the fire extinguisher nozzle rapidly with a 

side-to-side sweeping mtion. 

(2) The effective discharge time of m3st hand-held fire extinguishers 

ranges from 8-to-25 seconds depending on the capacity and type of the 

extinguisher. lXe to this relatively short effective time span, the proper 

selection and use of the fire extinguisher mst be mde without delay. 

(3) Care rust ba taken not to direct the initial discharge at the 

burning surface at close range (less than 5-to-8 feet) because the high 

velocity stream may cause splashing and/or scattering of the burning material. 

(4) Ventilate the ccmpartrnent promptly after successfully 

extinguishing the fire to reduce the gaseous combustion and gases produoad by 

thermal &composition. 

h. Inspection, Hydrostatic Test and Life Limits. Recommended procedures 

for the inspection, hydrostatic test and life limits of pressure cylinders are 

outlined in Part 173, Chapter 1, Subparts R, and G of CF'R 49 currently in 

effect. !?ee CFR49, Part 173.306(c)(5) regarding retest intervals for fire 

extinguishers. 

M. C. Beard 

Director of Airworthiness 

Par 8 
317184 

. 

AC 20-42C 

Appenaix 1 

FIGURE 1. @XXGRAPH 

-100 

40 

-60 

-40 

s-20 

-10 

E -0 

1; 

h 4 

I! 

1 

-2 

f 

-1.0 

-0.0 

-0.8 

-0.4 

-0.2 

-0.1 

100,000 

00,000 

~0,000 r 

-40,000 

-20,000 

-10,000 

=o,ooo 

E 4,000 

P r4,000 

it 

2,000 

; 1,000 000 e 600 I 

8 

I 400 

200 

i 

100 

80 

60 

40 

20 

IO 

CO2 SELECTOR 

W= .02tos+ 

NOTE: Due to the effect of CO2 on human mspiration rate, the 

allowable CO2 would be reduced by a factor of six from 

the amunt allowed by the ~02 nanograph to reduoz changes 

in human respiration rates (Ref. Paragraph 8f(5) of this AC). 

1