DEVELOPMENT OF A HALOTRONTM I HANDHELD FIRE 

EXTINGUISHER FOR USE ONBOARD COMMERCIAL AIRCRAFT

Bradford A. Colton and Jeff M. Gibson 

American Pacific Corporation 

3770 Howard Hughes Parkway, Suite 300, Las Vegas, Nevada 89109, USA 

Tel: (702) 735-2200; Fax: (702) 735-4876 

email: bcolton@apfc.com; jegibson@apfc.com

1. INTRODUCTION 

On June 17, 1993, through the Federal Register, the Federal Aviation Administration (FAA) 

announced it was embarking on the development of a halon replacement program [1]. A portion of 

this program was to determine a test protocol to certify halon 1211 replacement handheld 

extinguishers for use onboard commercial passenger aircraft. The development of the test program 

was a joint industry/government effort that resulted in the Minimum Performance Standards for 

Handheld Fire Extinguishers as a Replacement for Halon 1211 on Civilian Transport Aircraft [2]. 

This paper overviews the initial selection of halon 1211 for use onboard commercial aircraft and 

highlights events and testing for the Underwriters Laboratories (UL) listing and FAA approval of a 

Halotron I extinguisher that may be used onboard commercial aircraft. 

2. APPROVAL OF HALON 1211 EXTINGUISHERS 

In 1980, FAA Advisory Circular 20-42, Hand Fire Extinguishers for Use in Aircraft, was revised to 

20-42A in order to update the standard to current technology [3]. Revision to the circular included the 

approval of halon 1211 and 1301 extinguishers, which allowed the use of extinguishing agents with a 

toxicity rating of five or higher in occupied areas. At the time, most planes were protected by a 

combination of water and dry chemical, or water and carbon dioxide (CO2). 

Around the time of the 20-42A issuance, the first of a series of incidents occurred in which a hijacker 

would carry aboard a flammable liquid and threaten to set the plane on fire [3]. For protection 

against terrorist activities, testing of various extinguishing agents was carried out by the FAA that 

would impact future revisions of the Advisory Circular. Agents evaluated were water, CO2, dry 

chemical, halon 1211, and halon 1301. Table 1 presents data for the basic characteristics of the agents 

tested. 

Table 1. Extinguishing Agent Basic Characteristics 1

Agent Minimum 

Agent 

Weight 

Necessary 

for 10 B:C 

Rating, Lb. 

Minimum 

Agent 

Weight 

for 1 A 

Rating, 

Lb. 

Agent Plus 

Extinguisher 

for 5 B:C 

Rating, Lb. 

Around 

Object 

Capability 

Corrosion 

Potential 

Visibility 

in 

Confined 

Space 

Nominal 

Range, 

feet 

UL 

Toxicity 

Group 2

Halon 1211 5 9 4-6.5 Good No Good 9-15 5 

Halon 1301 13 N/A No units 

commercially 

available 

Good No Good 4-6 6 

Dry 

Chemical 

(ABC) 

2.5 2.5 5-10 3 Poor Yes Poor 5-12 Non-toxic 

CO2 10 N/A 12-20 Fair No Good 3-8 5 

Water N/A 10.4 N/A Poor N/A Good 30-40 Non-toxic 

1. This table is a reproduction of Table 11 in Reference 3. 

2. The UL toxicity Group 6 is the least toxic grouping. Group 5 is considered of a higher toxicity than Group 6. 

3. 10 B:C Rating 

As can be seen in Table 1, Halon 1211 stood out from the rest of the agents as it had the capability to 

extinguish fires around objects, good visibility, no corrosion or clean-up problems, a good throw 
range, and a low weight requirement. Halon 1301 provided some of the same benefits as halon 1211, 

but had a shorter throw range and was not commercially available in handheld units. 

Since halon 1211 was in a higher toxicity grouping than halon 1301, there was a concern about using

it in occupied areas. It became important to document the expected level of exposure based on

intended usage and ventilation rates. One test series involving human exposure was carried out by

the United States Coast Guard on C-130 aircraft facing a 25-30 knot wind [3]. In the testing, 

representing an onboard major electrical fire, three 5 Lb. halon 1211 extinguishers were discharged 

within one minute of each other at various locations. The first discharge was in the forward cargo

area, which was immediately behind the cockpit. The second discharge was inside the cockpit, with

the third discharge in the rear cargo area. Per normal flight procedures, the forward hatch in the 

cockpit, and the side doors in the rear cargo area, were opened in order to dissipate smoke and fumes. 

In this case, no live fire was present. As expected, the cockpit area reflected the highest agent

concentration due to its smaller size and lower ventilation rates. The average concentration of halon 

1211 in the cockpit area for the first 4 to 5 minutes was less than 3,000 parts per million. The 

maximum time that was required for total halon disappearance was 41 minutes. “None of the five 

participants in the exercise had any adverse effects from exposure either acute or cumulative.” It was 

noted that in actual flight, ventilation rates would have been greater than those used for this test,

resulting in reduced agent concentration and exposure time. 

Other tests with halon 1211 focused on the degree of layering that occurs with the discharge of 

handheld extinguisher [3]. Due to the reduced energy at discharge and considerably smaller degree of 

turbulence induced, the discharge of handheld extinguishers was found to have a layering effect as 

compared to a total flooding system. The handheld tests demonstrated that introducing halon 1211

into a volume by a streaming method resulted in significant concentration differences from the floor

level to the nose level. 

The FAA conducted a fire/toxicity test program focusing on a seat fire initiated by the ignition of a

flammable liquid, with a final report being issued in 1982 [4]. The tests compared halon 1211 to

water, CO2, and dry chemical (monoammonium phosphate), and evaluated the decomposition

products of halon 1211. These tests were carried out in a modified C-133. Modifications consisted of

dividing the cabin into two sections by a galley partition and modifying the ventilation rates to match

expected in-flight conditions. A triple-passenger airline seat was doused with 1 quart of gasoline and 

ignited. In these tests, water and CO2 were unable to completely extinguish the fire. In the case of

water, two extinguishers containing 1.5 quarts each were discharged for each test. In the case of the 

CO2, over 10 Lb. of agent was discharged for each test. Halon 1211 and dry chemical both 

successfully extinguished the fire. 

In these FAA seat fire tests, there were two sampling locations: one approximating the position that 

the extinguisher operator would be in front of the seat (sampling at 5 ft. 6 in. off the floor), and one 

located behind the seat (sampling at 1 ft. 6 in., 3 ft. 6 in., and 5 ft. 6 in. off the floor). The conclusions 

for halon 1211 from the sampling tests were: 

“Acid gases and 1211 concentrations were below ‘dangerous’ levels when a gasoline ignited seat

fire, in a simulated in-flight aircraft, was extinguished with Halon 1211”, 

• 

• 

• 

“Acid gases and 1211 disappear due to ventilation, diffusion, and adsorption effects”, and 

“Effective utilization of Halon 1211 to extinguish a severe seat fire in a transport passenger cabin 

is safe in term of agent decomposition.” 

The seat fire by itself produces toxic by-products. Both References 3 and 4 assert that if the fire is not 

quickly controlled that the hazard associated with the smoke and by-products will be much greater

than the risk of a quick extinguishment with halon 1211. 

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2.1 DEVELOPMENT OF HANDHELD MINIMUM PERFORMANCE STANDARD 

The FAA announcement in the 1993 Federal Register concerning their halon replacement program 

stated that they would focus on four applicable areas, one of which was “hand fire extinguishers” [1].

It was announcement that one of the tests “would be patterned after the in-flight fire which occurred

on trans-Atlantic Delta L-1011 flight on March 17, 1991.” On this Delta flight, insulation batting, 

electrical wiring, flooring, and sidewall paneling caught fire and spread through debris and 

contamination from years of servicing. Halon 1211 was discharged blindly into air return grills, 

successfully extinguishing the fire beneath the floor and saving the 231 passengers and crew onboard. 

There have been several incidents involving the successful extinguishment of hidden fires by halon 

1211 handheld extinguishers. Because the demonstrated risk of these “hidden” fires, the FAA has 

specified that agents replacing halon 1211 must exhibit a similar degree of protection against these

fires. The guidelines for the hidden fire and other testing are outlined in the Minimum Performance

Standards for Handheld Fire Extinguishers as a Replacement for Halon 1211 on Civilian Transport

Aircraft [2]. The standard requires a handheld extinguisher to pass two tests, the seat fire/toxicity test 

and hidden fire test, and have a 5B:C rating. The seat fire/toxicity testing is similar to that performed

for halon 1211, but the hidden fire test is being newly introduced. 

The origin of the hidden fire test fixture in the FAA minimum performance standard goes back to 

research that was funded by the Civil Aviation Authority (CAA) in the United Kingdom. A report, 

entitled “The Development of a Hidden Fire Test for Aircraft Hand Extinguisher Applications”, was 

published in 1995 for work that Kidde International had performed under contract [5]. The test 

fixture went through several configurations. Some of the changes made throughout the modification 

process were:

• Square test enclosure changed to tall, thin enclosure 

• 

• 

• 

• 

• 

Minimal ventilation changed to sizeable cut-outs 

Two fire locations expanded to 20 locations 

Allowable ambient temperature fluctuations changed to temperature conditioning (70 ± 1.8 o

F, 21 

±1 oC) 

High extinguisher discharge location to mid-height location 

Low baffles changed to only high baffles 

The final variation was intended to reflect “the ‘infinite’ aspect of an aircraft cheek area” and to have

a mid-height extinguisher discharge location to test for upwards dispersion. Even though the final 

variation had 20 fire locations possible, only 8 fires were lit at one time. 

Initial hidden fire tests using the Kidde/CAA test fixture were conducted with a constant-pressure

generic discharge apparatus. Final tests were performed using a few commercialized halon 1211

extinguishers. In these tests, notable variations were observed in the percent of fires extinguished

with handheld extinguishers of similar flow rates and starting agent weights. Table 2 reflects these 

test results and the importance of hardware, discharge time, discharge pressure, and agent quantity.

The hidden fire test prescribed in the new FAA minimum performance standard is similar to that 

described in the CAA report. The test fixture’s plastic view window was significantly enlarged and 

moved from the short side of the rectangular fixture to the long side of the unit for better viewing. 

There were two changes to the test protocol: (1) all 20 fire locations are ignited, instead of just eight, 

and (2) the fixture is allowed to be within a broader temperature range, 70 to 90 o

F (21.1 to 32.2 oC),

instead of 68 to 71.6 o

F (21±1 oC). Figure 1 is a photograph of the FAA hidden fire test fixture. 

3
Table 2. Halon 1211 Hardware Variations Tests for Kidde/CAA Hidden Fire Test 1

Extinguisher Pressure, psig Agent Weight, Lb. Mass Flow Rate, 

Lb./s 

Percent of Fires

Extinguished

Walter Kidde 130 2.0 0.31 40 

Walter Kidde 100 2.5 0.22 40 

First Technology 125 2.5 0.25 59 

Water Kidde ‘standard’ 130 2.5 0.27 45 

Walter Kidde 220 2.5 0.36 51 

Walter Kidde 130 3.0 0.23 50 

Kidde Thorn 130 3.3 0.32 60 

Chubb 145 3.3 0.19 50

1. This table based on a compilation of information from Tables 4.2 and 4.3 in Reference 6. 

Figure 1. Photo of FAA Hidden Fire Test Fixture 

3. TESTING WITH HALOTRON I 

In October of 1999, a standard 5B:C UL listed Amerex 5.0 Lb. Halotron I extinguisher was tested

against a portion of the FAA draft of the minimum performance standard for handheld fire

extinguishers. The 5.0 Lb. extinguisher was chosen because it already had the required 5B:C rating. 

The testing performed was the seat cushion/toxicity test, which is similar to that performed for the 

approval of halon 1211 (as described above in Section 2). Figure 2 represents a schematic of the test 

setup, reflecting the locations where the neat agent concentration and fire by-products are sampled.

The sampling locations at each station were at 3 ft. 6 in. and 5 ft. 6 in. off the floor. The tests were

conducted in the FAA TC-10 test fixture, which is an AFT section of a DC10. To pass this seat

cushion/toxicity test, the seat fire must be extinguished with the associated levels of hazardous gases 

not exceeding dangerous levels. The hazardous gases include those generated by the interaction of 

the agent and the fire, as well as the neat agent. One quart of gasoline is poured over the seats, 

ignited, and allowed to burn for 30 seconds before discharging the extinguisher. Halotron I was 

4
able to easily extinguish the seat fires with just a portion of the agent in the extinguisher. The peak 

agent and by-product concentrations from these tests are summarized in Table 3.

When reviewing the peak neat agent concentrations in Table 3, these can be compared to the accepted

industry practice of relating these values to the cardiac sensitization levels. The cardiac sensitization 

levels for Halotron I are 1.0%vol. for the No Observable Adverse Effect Level (NOAEL) and 2.0%

for the Lowest Observable Adverse Effect Level (LOAEL). The highest concentration of neat agent 

in all tests never exceeded 0.1%vol, reflecting a high degree of safety margin against both the 

NOAEL and LOAEL. In Reference 4, the dangerous concentration range for HCl is identified as 

1,000-2,000 ppm, 50 to 250 ppm for HF. In the minimum performance standard, Reference 2, the 

levels of HF should not exceed 100 ppm for a five minute period, nor shall the HF level exceed 200 

ppm for a one minute period. Table 3 indicates that HCl and HF were both well below acceptable 

levels. 

NOTE: This figure is a reproduction of Figure 1 from Reference 2 

Figure 2. Seat Fire/Toxicological Test Instrumentation (TC-10 Test Article) 

5
Table 3. Summary of Halotron I Seat Cushion/Toxicity Tests 

Test Run Agent Amount 

Required to 

Extinguish Seat 

Fire, Lb. 

Comments on Fire 

Extinguishment

Peak Neat Agent 

Concentration,

%vol. 

Peak HCl, ppm Peak HF, ppm 

1 2.1 Small fire at seat 

top - required 2nd

short discharge to 

complete

extinguishment 

0.10 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

11 (occurring at 

station 330, 5 ft. 6 

in. probe) 

28 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

2 2.0 Fire readily

extinguished 

0.07 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

22 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

29 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

3 2.3 Fire readily

extinguished 

0.10 (occurring at 

station 330, 5 ft. 6 

in. probe) 

12 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

24 (occurring at 

station 80, 5 ft. 6 in. 

probe) 

With the completion of the seat fire/toxicity test, and with the UL 5B:C rating, the final test was the 

hidden fire test. The hidden fire text fixture was initially at the FAA Technical Center in Atlantic 

City, where preliminary Halotron I testing with Amerex extinguishers was completed in 2000. The 

test fixture was later moved to the UL Fire Test facility in Northbrook, IL. There is an agreement

between the FAA and UL that UL will conduct the hidden fire tests. UL will provide a listing for

agents that have: (1) previously passed the seat fire/toxicity test, (2) passed the testing to obtain a 

5B:C, (3) passed the hidden fire test, and (4) are contained in an extinguisher that can pass the other 

operational tests required by UL Standards such as 2129, Halocarbon Clean Agent Fire 

Extinguishers. 

The hidden fire tests with HalotronTM I were conducted at UL in December 2001. In performing these 

tests, it became necessary to modify the pressure and agent weight of Amerex’s standard 5.0 Lb. 

Halotron I extinguisher. To successfully pass the hidden fire test requires extinguishing a minimum 

average of 9 cups out of 20 (45% of fires) over a series of five tests. A summary of the tests

performed using the standard Amerex 5.0 Lb. cylinder, valve, and Halotron I nozzle design is 

provided in Table 4. 

Table 4. Amerex Handheld Extinguisher Hidden Fire Tests with Halotron I 

Line Number Agent Weight, Lb. Pressure, psig Mass Flow Rate, 

Lb./s 

Percent of Fires

Extinguished

Preliminary FAA Technical Center Testing, Atlantic City, 2000 

1 5.0 100 0.48 35

2 5.0 150 0.55 45

3 5.0 125 0.50 35

4 5.0 150 0.50 45

UL Northbrook Facility Testing, 2001 

5 5.0 150 0.54 45

6 5.0 150 0.56 35

7 5.0 125 0.52 40

8 5.5 150 0.56 50 

9 5.5 150 0.56 45 

10 5.5 150 0.56 50 

11 5.5 150 0.56 45 

12 5.5 150 0.56 50 

 NOTE: Grey shading on Lines 8 through 12 reflect the series of five tests for the final extinguisher configuration. 

Tests 8 through 12 represent tests of the final configuration that will receive UL listing/FAA approval. 

Due to the changes in agent weight and pressure, the final configuration had to be re-tested on the 5B 

6
fire, which it passed. As was observed in the CAA report on the development of the hidden fire test

fixture, there can be variations of the number of cups extinguished, even with the same configuration. 

Figure 3 represents the hidden fire locations that were extinguished by Halotron I in Tests 8 through 

12 in Table 4. In general, these locations follow the typical locations that are extinguished by halon 

1211 based on Reference 5. One exception is that the fire at the top left in the fixture (fire closest to 

the upper vent), which could sometimes be extinguished by halon 1211, was never extinguished with 

Halotron I. The difference in extinguishment of the top left cup is believed to be a reflection of the 

difference in boiling point between Halotron I and halon 1211. Halotron I has a boiling point of 

80 o

F (27 oC), compared to halon 1211 at 26 oF (-3.4 oC). The fires extinguished by Halotron I in 

these tests were extinguished by the end of the discharge or within a couple seconds thereafter.

During the tests, a considerable amount of Halotron I pooled at the bottom of the test fixture. While 

the evaporation of the pooled agent was strongly evident, the size of the vents did not allow for this 

accumulated liquid to be available to extinguish further fires. 

Fire Never 

Extinguished

Often 

Extinguished

Fire Always 

Extinguished

Solid Stop Plates

Perforated baffles

33% hole area

Vent

(400x125mm)

(15.75 x 4.90 in)

Vent

(400x125mm)

(15.75 x 4.90 in)

Figure 3. Fire Extinguishment Locations for Halotron I 

4. CONCLUSION 

The use of halon 1211 onboard aircraft was widely studied before its selection. Since the approval of 

halon 1211, its use has saved hundreds of lives onboard commercial aircraft. Some of the incidences

in which halon 1211 successfully extinguished fires were fires hidden behind sidewalls or other 

hidden spaces. Because of the performance of halon 1211 in real fire situations, the FAA recognized 

early on that new agents must achieve the same level of performance. The approval process for

agents replacing halon 1211 is more rigorous than that used for halon 1211. 

A Halotron I handheld extinguisher has successfully completed all testing required by the FAA 

Minimum Performance Standards for Handheld Fire Extinguishers as a Replacement for Halon 1211

7
on Civilian Transport Aircraft. The tests completed demonstrate that Halotron I can provide a 

similar level of protection as halon 1211 and will not represent a hazard to passengers or crew based 

on neat agent concentration or by-products when used properly. Final UL listing and FAA approval 

of the Amerex Halotron I handheld extinguisher discussed in this report represents the first

extinguisher containing an environmentally acceptable agent to have fully satisfied the requirements 

to replace halon 1211 onboard commercial aircraft. Halotron I handheld extinguishers for use 

onboard commercial aircraft are anticipated as being commercially available in early Summer 2002. 

Halotron I handheld extinguishers are available from three other manufacturers in North America, 

and it is anticipated that there will be other UL/FAA approved extinguishers containing Halotron I 

in the near future. 

5. ACKNOWLEDGEMENTS 

The support from Amerex was instrumental in allowing us to use data from their extinguishers. Also,

Adam Chattaway from Kidde Research most helpful for being available to discuss his work and report 

on the development of the CAA hidden fire fixture. 

6. REFERENCES 

1. Federal Aviation Administration. Halon Replacement Performance Testing. Notice 93-1. 

Federal Register Vol. 58, No. 115, Thursday, June 17, 1993. pp. 33477-33481. 

2. FAA. “Minimum Performance Standards for Handheld Fire Extinguishers as a Replacement for 

Halon 1211 on Civil Transport Aircraft.” April 2000 FAA Draft. [Final draft to be released 

shortly as document DOT/FAA/AR-01/37]

3. Krasner, L. M. “Study of Hand-Held Fire Extinguishers Aboard Civil Aviation Aircraft.” Report 

Prepared by Factory Mutual Research Corporation for the U.S. Department of Transportation, 

Federal Aviation Administration. DOT/FAA/Ct-82/42. Final Report, April 1982. 

4. Hill, Richard G., L. C. Speitel. “In-Flight Aircraft Seat Fire Extinguishing Tests (Cabin Hazard

Measurements).” DOT/FAA/CT-82/111. U.S. Department of Transportation, Federal Aviation 

Administration: Atlantic City Airport, NJ. Final Report, December 1982. 

5. Chattaway, Adam. “The Development of a Hidden Fire Test for Aircraft Hand Extinguisher 

Applications.” Report Prepared by Kidde International Research for the Civil Aviation Authority 

(CAA). CAA Paper 95013. 1995. 

8