SUITABILITY OF CF3I TO REPLACE HALON 1301 AS THE INERTING 

AGENT IN WING FUEL TANKS ON THE F-16 AIRCRAFT 

Richard G. Gann

Building and Fire Research Laboratory 

National Institute of Standards and Technology

Gaithersburg, MD 20899-8664 USA 

Tel: (301) 975-6866; Fax: (301) 975-4052; e-mail: rggann@nist.gov 

ABSTRACT 

At the request of the Under Secretary of Defense (Acquisition, Technology and Logistics), the 

Director of Defense Research and Engineering convened an Independent Review Panel (IRP) to 

assess the four critical technical issues and comment on how they might affect implementation of 

CF3I as a viable substitute for halon 1301 in the F-16 inerting application. 

The four technical areas identified as critical to the assessment were: materials compatibility, low 

temperature performance, human toxicology, and atmospheric chemistry. The questions to be 

answered were: was the research conducted scientifically, is there sufficient information on CF3I 

to decide whether it is an acceptable alternative to halon 1301 for wing tank inertion on the F-16, 

and if not, what additional Science and Technology research is required?

The conclusions of the IRP were as follows: 

• CF3I is more chemically reactive than halon 1301. After further qualification testing, it 

may be possible to specify materials that could be used in service with CF3I. 

• CF3I is inadequate as a replacement for halon 1301 in the existing F-16 system due to its 

higher boiling point and resultant reduced delivery pressure at low temperatures. 

• CF3I is more toxic than halon 1301. It would be unwise to replace a chemical with a 

more toxic one. More rigorous toxicity testing of CF3I would provide a more quantitative 

estimate of its toxicity in realistic exposure scenarios. 

• Ozone depletion from F-16 application of CF3I could be as small as one eighth that of 

halon 1301 (at lower altitudes) or as large as one and two-thirds times as damaging as 

halon 1301 (at higher altitudes). In any case, CF3I use onboard an F-16 would be a Class 

I substance if significant amounts are released above 20,000 ft, and the U.S. Clean Air 

Act bans use of Class I substances. 

HALON 1301 USE IN THE F-16 

The Air Force currently uses halon 1301 (CF3Br) to inert the wing tanks of its front line F-16 

fighter aircraft while the aircraft is in a combat zone or other area known to be hostile, i.e., when 

the pilot believes there is the potential for hostile action that might cause ignition of fuel in the 

fuel tanks should a direct hit be taken. There are 1,400 aircraft in the F-16 fleet (not including 

those sold to foreign governments), and the Air Force continues to discharge at least 5,000 kg 

(10,000 lb) of halon 1301 into the atmosphere each year. This figure could rise 10- to 20-fold if 

there were a major regional conflict.

1
A schematic of the F-16 fuel tank inerting system is shown in Figure 1. The wing fuel tanks are 

inerted by halon 1301 vapor from a single, non-heated storage bottle. Once activated by the 

pilot, there is a 20 s burst that releases about half the agent. The control valve then resets to 

provide a 45 min continuous bleed of agent (ca. 1 lb/min) against ambient atmospheric pressure. 

This action maintains an inerting concentration of agent in the ullage space above the liquid fuel 

in the tank. During this bleeding phase, there is a continuous purge of the fuel tank head space to 

the outside atmosphere. The agent left in the bottle is vented as the aircraft climbs after its 

missions, usually towards refueling at ca. 10 km (30,000 ft). A sizable fraction of the total load 

could be released during this operation. 

Figure 1. Components of the F-16 Fuel Tank Inerting System

4

KEY

5. Vent and Pressurization

(V&P) Valve

6. Overboard Vent Outlet

1. Halon Reservoir Bottle

2. Solenoid Shutoff Valve A

3. Engine Bleed Air (from ECS)

4. Halon Flow Control Valve

RIGHT

WING

TANK

7. Solenoid Shutoff Valve B

8. Check Valve

9. Restrictor Orifice

(0.1 lbs per minute flow rate)

2

9

AFT TANK

LEFT

WING

TANK

FORWARD TANKS

8

1

VENT

VENT

VENT

FUEL VENT VENT

TANK

7

3

5

6

There is no one standard flight profile that can be used to specify exactly when, where, and at 

what altitude inerting of the wing tanks will occur. Air Force data indicate that the F-16 can 

operate between ground level and 20 km (ca. 60,000 ft), and inerting of wing tanks normally 

occurs between 6 km (ca. 20,000 ft) and 14 km (ca. 45,000 ft). 

PROJECT BACKGROUND 

The Air Force will eliminate present halon 1301 usage on the F-16 through the phased

replacement of the F-16 aircraft by the Joint Strike Fighter (JSF), which does not use halon 1301. 

These new production aircraft will use alternatives such as HFC-125 or an On Board Inert Gas 

2
Generating System (OBIGGS). The JSF will reach Air Force initial operating capacity in 2011, 

and the F-16 will completely retire from the Air Force inventory by 2024. 

To be responsive in the interim period, the Air Force has evaluated several halon 1301 

alternatives. To be effective in the F-16, such an alternative would have to be a true “drop-in” 

replacement due to the time necessary to accomplish any retrofit engineering on the F-16 fleet 

prior to the complete phase-in of the JSF. 

CF3I was one of these potential alternatives. However, after completing an evaluation of CF3I in 

1999, the Air Force decided not to use it based on unresolved material compatibility, poor low 

temperature performance (condensation) and distribution, higher toxicity than halon 1301, and 

potentially harmful atmospheric chemistry.1

 There was also a concern regarding extensive 

modifications required to the F-16 fuel tank inerting system. 

The decision was controversial, and in 2002 The Director of Defense Research and Engineering 

requested that an independent Review Panel of distinguished scientists and technical experts 

independently review the four critical technical areas of interest: 

1. Materials Compatibility: The IRP should review test results for CF3I compatibility

with metals, gasket materials, and lubricants to ascertain whether sufficient data are 

available to determine if CF3I is compatible with the F-16 airframe materials. If this is not 

the case, then the IRP should identify the critical failure points and what additional 

testing needs to be performed. 

2. Low Temperature Performance: An effective fire suppressant in a fuel tank inerting 

mode must maintain sufficient vapor pressure to inert adequately against a munitionignited fire. The boiling point of the suppressant relative to the temperature of the 

surroundings can significantly affect the performance of the compound. The IRP should 

review test data to determine whether the higher boiling point of CF3I relative to CF3Br 

would result in diminished fire inerting capability. 

3. Human Toxicology: Toxicological testing and analysis should consider risks of human 

exposure to CF3I under normal operating conditions and maintenance procedures. 

Previous testing and analysis should be reviewed for their sufficiency to enable the safety 

of personnel in appropriate exposure scenarios. 

4. Atmospheric Chemistry: Halon 1301 has a significant ODP due to its chemical 

stability in the troposphere and its photolysis in the stratosphere. CF3I has different 

behavior in both the troposphere and stratosphere that is in need of review to determine 

its impact on the ozone layer as a function of the altitude at which the compound is 

released. 

In each area, they were to answer the following three questions: 

• Was the prior research conducted scientifically to produce the resulting data?

• Is there sufficient information on CF3I to decide whether it is an acceptable alternative to 

halon 1301 for wing-tank inert use on the F-16? 

• If not, what additional S&T research is required? 

3
The following were the participants in the study: 

Review Director 

Mr. Robert Boyd, Office of the Director of Defense, Research and Engineering (DDR&E) 

Moderator for Materials Compatibility/Low Temperature Performance 

Mr. William Leach, Fire Protection Team Leader, Naval Air Warfare Center 

Materials Compatibility Panel Members 

Dr. Richard Ricker, Materials Science and Engineering Laboratory, National Institute of 

Standards and Technology 

Dr. Steven Lawrence, Chemistry Division, U.S. Naval Research Laboratory 

Low Temperature Performance Panel Members 

Dr. Jiann (John) Yang, Fire Research Division, National Institute of Standards and Technology

Dr. Marino di Marzo, FireProtection Engineering Department, University of Maryland 

Moderator for Human Toxicology and Atmospheric Chemistry 

Dr. Richard Gann, Fire Research Division, National Institute of Standards and Technology, and 

Technical Program Manager, Next Generation Fire Suppression Technology Program 

Human Toxicology Panel Members

Dr. Edgar Kimmel, Toxicology Detachment, Wright-Patterson Air Force Base 

Dr. Steven Packham, State of Utah Department of Environmental Quality 

Atmospheric Chemistry Panel Members 

Dr. Susan Solomon, Aeronomy Laboratory, National Oceanic and Atmospheric Administration 

Dr. Malcolm Ko, Atmospheric and Environmental Research Inc. 

Dr. Donald Wuebbles, Department of Atmospheric Sciences, University of Illinois 

Other Technical Resources: 

Mr. David Sassaman, F-16 Fuels System Engineer, Lockheed Martin Aeronautics Company 

Mr. Sherman Forbes, Office of the Secretary of the Air Force 

Major Robert Torrick, Occupational Requirements Directorate, U.S. Air Force 

Dr. Leslie Chaney, U.S. Army Center for Health Promotion and Preventive Medicine 

The IRP meeting was organized and hosted by HydroGeoLogic, Inc. on August 21 and 22, 2002. 

The report was issued in September 2002.2

 The following sections relate the sub-panel 

assessments of the extensive reading materials and their experience, and analyses performed for 

this project.

MATERIALS COMPATIBILITY 

When selecting or changing a material used in a critical application such as an aircraft, the 

candidate material is required to demonstrate that it can survive the service conditions including 

the whole range of loads, temperatures and chemical compositions of the operations, service, and 

4
storage environments. Years of operating experience have not revealed any major 

incompatibility problems between halon 1301 and the more than 2,000 different metal and 

polymer components are found in the F-16 inerting system. 

Materials compatibility tests with CF3I have to date have been in the laboratory only, with no 

systems qualification testing. The laboratory work indicates potential compatibility problems. 

Data from a series of tests at the National Institute of Standards and Technology (NIST)3, 4

(Table 1) showed that CF3I exhibited higher corrosion rates for all materials tested than halon 

1301. One case of stress corrosion cracking (SCC) was evidenced. Both NIST and Lockheed 

Martin5

 found significant interactions of CF3I with elastomers, possibly due in part to impurities 

in the CF3I. As a consequence of these studies, both the Air Force Research Laboratory6

 and 

Lockheed Martin5

 have recommended that further materials compatibility testing be conducted. 

Table 1. Comparison of Corrosion Rate Data7

 

Material Halon 1301 Std. Error Cf3i Std. Error Ratio 

 g/m2d g/m2d CF3I/CF3Br 

Nit 40 0.00042 0.00012 0.0014 0.0003 3.5

AA6061-T6 0.01262 0.0074 0.0396 0.18881 3.1

304 Stainless 0.00060 0.00016 0.0040 0.00055 6.8

Ti 15-3-3-3 0.00051 0.00007 0.0025 0.00048 5.0

AISI 4130 0.02791 0.01395 0.55297 0.06940 19.8

The panelists concurred and also noted that there remained issues of knowing the levels of 

impurities that are tolerable (necessary for specifying the procurement), the effect of dynamic 

service conditions. 

The answers to the questions were: 

1. Was the research conducted scientifically? Yes. The relevant work from NIST was 

planned carefully, conducted properly, and documented thoroughly. The Lockheed Martin 

compatibility testing also appears to have been conducted in an appropriate manner, given the 

limited scope that defined it. Neither study was designed to emulate fully the conditions of the 

F-16 fuel tanks. 

2. Is there sufficient information on CF3I to decide whether it is an acceptable alternative to 

halon 1301 for wing tank inert use on the F-16? No, nor is there sufficient information to reject 

it from further consideration. The NIST work was not specifically directed toward fuel line 

materials in an F-16, although many of the materials and environments studied are relevant. The 

Lockheed Martin study was too brief and too narrowly defined to make an informed decision 

regarding CF3I qualification. Moreover, pass/fail criteria have not been established for this 

application, so the performance of halon 1301 becomes the only benchmark. CF3I proved more 

aggressive than halon 1301 in many of the comparison tests of these studies, and hence caution 

should be exercised when proceeding to qualify this agent for such a critical application as this. 

5
3. If not, what additional S&T research is required? Carefully designed flight qualification 

tests followed by monitored (limited) service with engineering performance evaluations should 

be conducted with CF3I before converting agents. The cause of the observed SCC in Ti alloy 

should be investigated to ensure that this will not occur with alloys that are in the fuel system. 

The origin of the reaction with Cu should be investigated to determine why it occurred and why 

other alloys should not be susceptible to this or similar reactions. 

LOW TEMPERATURE PERFORMANCE 

Halon 1301 has a very low boiling point, and thus a relatively high vapor pressure at the low 

ambient temperatures found at the operational altitudes of the F-16 aircraft. When activated, 

halon 1301 transfers from the storage bottle to the wing tanks under its own vapor pressure to 

provide the necessary concentration to inert the fuel in the tank. The main issue associated with 

low temperature performance of CF3I is its higher boiling point and resulting reduced vapor 

pressure relative to halon 1301. Further, a recent study8

 of cold discharge of CF3I in an engine 

nacelle (not wing tank) showed that some pooling occurred. 

At the minimum temperature prescribed by the F-16 operational envelope, ca. -62 °C (-80 °F), 

the vapor pressure of CF3I is 13.9 kPa.9

 As the airplane altitude increases, the fuel tank pressure 

decreases. At 30 km (ca. 60,000 ft), the highest altitude at which the five suppressant would be 

released, the atmospheric pressure is 7.1 kPa. This is the minimum possible value of the 

atmospheric pressure within the operating envelope. The V&P valve (Figure 1) keeps the fuel 

tank at 17 kPa to 25 kPa above the atmospheric pressure in a combat situation. This means the 

fuel tank pressure is at least 24 kPa. Therefore, CF3I cannot flow out of the bottle since it is at a 

lower pressure than the fuel tank (7.1 kPa vs. 24 kPa). A similar analysis for an operating 

temperature of -40 °C (-40 °F) shows that the agent would be viable between 30 km and 12 km

(38,800 ft), but not lower. 

Under these conditions, one also has to consider the possible mass flux of agent. The agent must 

flow at a rate sufficient to flush the tanks and to achieve the desired inerting concentration. 

Halon 1301 is delivered at 0.4 kg/s (085 lb/s) to achieve this objective. The critical discharge 

mass flux for a vapor varies linearly with the agent vapor pressure and with the square root of the 

molecular weight. At -40 °C, CF3I will flow at about one fourth the rate of halon 1301 in the 

same system. At this reduced flux the agent would not be able to displace fuel vapor and air in 

the tank. One could resize the system to achieve similar flow. However, that would require 

increasing the flow area of some of the system components fourfold. 

To achieve a performance similar to that of halon 1301, the simplest approach would be to 

increase the storage bottle pressure by maintaining it at a higher temperature. For CF3I to supply 

the burst of 0.4 kg/s the bottle temperature needs to be ca. –22 °C (-8 °F), requiring about 4 kW. 

The piping system feeding the agent to the fuel tanks also would have to be heated appropriately. 

During this delivery of the agent into the colder fuel tank, two competing phenomena are 

occurring: most of the agent would condense in a mist due to the drop in temperature, while the 

remaining vapor contributes to the total pressure according to its molar fraction. The fine 

droplets in the mist may vaporize as they mix with the gases in the fuel tank but this process is 

not fast at low temperature.8

 Should the droplets hit the liquid fuel, it is likely that liquid CF3I 

6
will become segregated at the bottom of the fuel tank and some of the agent will not be available 

for inerting the tanks. This removal of some of the agent introduces a significant level of

uncertainty as to the performance of the system over the required 45 min. 

The answers to the questions were: 

1. Was the research conducted scientifically? Yes. 

2. Is there sufficient information on CF3I to decide whether it is an acceptable alternative 

to halon 1301 for wing tank inert use on the F-16? Yes. 

HUMAN TOXICOLOGY 

In all cases of toxic risk assessment, risk is directly proportional to toxic potency. There is very 

low risk to life from inhalation of the suppressant during the actual inerting of F-16 wing tanks 

using either halon 1301 or CF3I. However, system maintenance and repair, routine recharging of 

vented tanks, storage, and material transport occasions must be considered. Here, historically 

there is very little risk attendant with use of the current system that employs halon 1301. There 

are no comparable precedents to evaluate potential risk scenarios involving CF3I. The system

reliability factors for CF3I remain unknown, especially if implementation of CF3I involves a 

significant engineering retrofit. Therefore, the actual health risks that might be associated with 

implementing use of CF3I cannot be estimated or quantified. It is possible to estimate the 

relative risk of halon 1301 vs. CF3I based on toxic potency. 

For these compounds, the toxic potency has been equated to the lowest observable adverse effect 

level (LOAEL) for cardiac sensitization. This is measured using an experimental protocol in 

which dogs are administered epinephrine in conjunction with agent exposure, simulating a 

physiologic condition of stress. The LOAEL values reported for halon 1301 and CF3I are 7.5 

volume % and 0.4 volume %, respectively. The design concentration for halon 1301 is cited as 

5.0 volume %, which is below the LOAEL; the design concentration for CF3I is 7.0 volume %, 

which is almost 20 times greater than its LOAEL. It is difficult to advocate the use of an agent 

when the concentration shown to elicit a lethal toxic effect is lower than the concentration 

required for the agent’s intended use. 

There are questions about the validity of the LOAEL values. The epinephrine challenge used in 

the protocol is about 10 times greater than endogenous epinephrine release rates in humans under 

stress. In addition, the LOAEL for CF3I was set relying on responses observed in only two 

animals, one each in two experimental groups lading to a question of statistical accuracy.10 An 

additional issue regarding CF3I cardiac sensitization involves the anecdotal report of two human 

volunteers repeatedly breathing this material.11 A physiologically based–pharmacokinetic model 

using estimates of applicable breathing parameters was used to simulate the blood levels of CF3I 

in these individuals. These simulations estimated peak blood levels 100 times larger than peak 

blood levels associated with exposures used to set the LOAEL for this material, indicating that 

concentrations higher than the measured LOAEL might be safe for people. However, the inhaled 

concentrations of CF3I were not verified, no scientific method was used to measure an effect, and 

factors related to possible tolerance from repeated trials were not demonstrated nor considered. 

7
In the absence of data for characterizing actual risk, a hypothetical scenario can illustrate the 

relative precautions for storing and handling of CF3I vs. halon 1301. Consider the situation in 

which the failure of a single container of either agent would result in an untenable environment, 

i.e., the concentration would exceed the LOAEL. In a 3 m x 3 m x 2.4 m (10 ft x 10 ft x 8 ft) 

room, one could store halon 1301 in containers holding 8 kg (ca. 18 lb) of the chemical, but CF3I 

would need to be stored in bottles holding no more than 0.5 kg (ca. 1 lb) to maintain the same

level of safety. 

The answers to the questions were: 

1. Was the research conducted scientifically? Most of the research appeared to be well 

done and the analysis of the data was appropriate. However, a single determination of CF3I 

cardiac sensitization is not sufficient. In the case of the human inhalation simulation there are no 

hard data to verify the concentration of the material inhaled and the “study” was not conducted 

under controlled scientific conditions. 

2. Is there sufficient information on CF3I to decide whether it is an acceptable alternative to 

halon 1301 for wing tank inert use on the F-16? Yes. Current information is sufficient to make 

a reliable scientific comparison between halon 1301 and CF3

I on the basis of toxic potency. 

ATMOSPHERIC CHEMISTRY 

Early studies examining the potential effects of CF3I on stratospheric ozone assuming emissions 

at the Earth’s surface studies resulted in extremely small ozone depletion potential (ODP) 

estimates for CF3I due to surface emissions: <0.00812 and 0.006.13 A new analysis conducted for 

this project determined a value of 0.012. In contrast, the ODP for halon 1301 (CF3Br) is about 

12. The use of any chemical with an ODP greater than 0.2 is to be controlled under the current 

U.S. Clean Air Act, and the U.S. Environmental Protection Agency gives careful consideration 

to controls on chemicals with ODP values as small as 0.05. 

The small ODP values for CF3I result from its very short atmospheric lifetime, approximately 4 

days in the latest model studies. CF3I will quickly decompose by absorption of sunlight, and the 

iodine released will be removed in the lower troposphere through rainout. Only a tiny fraction 

can reach the stratosphere to destroy ozone. CF3Br, on the other hand, absorbs sunlight much 

less effectively, and has an atmospheric lifetime of about 60 years. CF3Br therefore reaches the 

stratosphere even if emitted at the surface. Once in the stratosphere, most of the reactive Br 

atoms are released directly into the ozone layer where they can affect ozone. 

Almost all of the emissions of CF3Br (and thus CF3I if used as a replacement) from its use as an 

inerting agent in F-16s occur above 6 km (20,000 feet) altitude up to a peak altitude of 14 km

(ca. 45,000 feet). Released at these altitudes, some or all of the reactive iodine is available 

above the altitude where it can be rained out, and will all be available to react with ozone. It is 

estimated that about 0.1 mole % is transported to the stratosphere from surface release, with the 

fraction increasing up to about 10 mole % for releases in the upper troposphere, and 100 mole % 

for direct release in the stratosphere. Because of its long lifetime, the fraction of CF3Br reaching 

8
the stratosphere is essentially independent of whether it is released near the ground or directly 

into the stratosphere. This is shown pictorially in Figure 2. Short-lived molecules like CF3I 

could have a larger short-term impact in the ozone layer even if the cumulative effect is 

smaller,14 but the stratosphere would be cleansed of the emitted iodine soon after any 

discontinuing use of CF3I as an inerting agent. 

Figure 2. Halogen Transport to the Stratosphere from Use of Fire Suppression Agents 

Once in the stratosphere, iodine atoms are 3 to 6 times as potent as Br atoms at destroying ozone. 

(See Figure 3.) Including transport effects, the panelists estimated CF3I release from F-16 

aircraft as being between 13 % and 167 % as damaging to the ozone layer as equivalent usage of 

CF3Br. The variance results from the range of possible values for the ozone destruction 

efficiency of I relative to Br, the fraction of agent released by the aircraft directly into the 

stratosphere, and the fraction of agent reaching the stratosphere from lower altitude release. 

Reduction in the uncertainties associated with these estimates would require further analyses 

using numerical models of global atmospheric chemistry and physics. Three-dimensional 

modeling studies would be required to fully assess the effects of emissions from the aircraft. The 

above numbers imply a steady-state ODP for CF3I in the F-16 application of 0.82 to 10.9. 

Compounds with an ODP above 0.2 are Class I ODSs under the United States Clean Air Act. 

9
Figure 3. Relative Ozone Destruction Efficiency at Mid-Latitudes15 

The answers to the questions were: 

1. Was the research conducted scientifically? Yes. 

2. Is there sufficient information on CF3I to decide whether it is an acceptable alternative to 

halon 1301 for wing tank inert use on the F-16? Yes. The information provided 

suggests that release of CF3I at the stated flight conditions could cause greater ozone 

depletion than halon 1301, particularly for flights/CF3I release at higher latitudes. 

3. If not, what additional S&T research is required? Additional understanding of the actual 

location of the emission (altitude and latitude) coupled with additional modeling would 

narrow the uncertainties associated with the estimates and help better assess if CF3I is 

less harmful to the ozone layer compared to halon 1301 in specific cases. 

10
INDEPENDENT REVIEW PANEL CONCLUSIONS 

MATERIALS COMPATIBILITY 

• The information provided does not indicate that qualification testing or trials can be 

dispensed with on the basis of similarity of CF3I to CF3Br. 

• CF3I is more chemically reactive than halon 1301, which could lead to metal corrosion or 

elastomer failure. CF3I should not be accepted for inerting application on the basis that it 

corrodes like materials faster than halon 1301. 

• More quality/service testing is required on the materials compatibility of CF3I before it 

could be recommended as a replacement for halon 1301. After further service testing, it 

would be possible to specify materials that could be used in service with CF3I. 

LOW TEMPERATURE PERFORMANCE 

• CF3I is inadequate as a replacement agent for halon in the existing F-16 system due to the 

reduced delivery pressure of the CF3I at low temperatures. 

• Modifications of the system to increase the CF3I delivery pressure may rely on heating 

the storage bottle and the connecting piping. This approach is somewhat piecemeal since 

condensation at the injection point in the fuel tank may remove a portion of the agent, 

thus reducing the overall inerting performance. 

• If the agent storage bottle and distribution lines were heated, uncertainty remains in 

regard to condensation of the CF3I in the fuel tank, which would compromise (or even 

totally negate) its inerting ability. More testing is necessary before a retrofitted system

could be designed. 

• It is possible to calculate and experimentally evaluate the impact of condensation in the 

fuel tank. However, the inherent variations in the operation of the F-16 aircraft (i.e., its 

altitude excursions) introduce a significant level of uncertainty in the performance of the 

CF3I inerting system. 

HUMAN TOXICOLOGY 

 

• CF3I is more toxic than halon 1301. More rigorous toxicity testing of CF3I would 

provide a more quantitative estimate of its toxicity in realistic exposure scenarios. 

• CF3I is a more potent cardiac sensitizer than halon 1301. This is illustrated by fact that 

given a comparable exposure duration, the exposure concentration causing ventricular 

fibrillation is 18.75 times greater for halon 1301 than CF3I. 

• CF3I presents a greater health risk than halon 1301. Current data are insufficient to 

estimate health risks associated with implementing use of CF3I. 

11
ATMOSPHERIC CHEMISTRY 

• The ODP of CF3I is highly dependent upon the altitude and latitude at which it is 

released. It was calculated that CF3I usage onboard an F-16 aircraft could be between 

13% and 167% as damaging to the ozone layer as usage of halon 1301. In other words, 

ozone depletion from F-16 application of CF3I could be as small as one eighth that of 

halon 1301 (at lower altitudes) or as large as one and two-thirds times as damaging as 

halon 1301 (at higher altitudes). However, even for conservative choices, CF3I use 

onboard an F-16 would be a class I substance if significant amounts are released above 

20,000 ft, and the US Clean Air Act bans use of class I substances. 

• ODP is a measure of the cumulative effects (time integrated) on ozone from emission of 

an ODS. The effect from emitted halon 1301 is spread over several decades while that 

from CF3I will last only several years. Thus, even for the case when the cumulative 

effects from CF3I is one eighth of that from halon 1301, the immediate short term effect 

on ozone will still be comparable. 

• These updated calculations indicate that there is not a clear-cut environmental advantage 

of CF3I over halon 1301. Since this is the reason for proposing the change, CF3I is not an 

acceptable alternative unless the results of more detailed modeling indicate a contrary 

position. 

REFERENCES 

1

 Forbes, Lt. Col. S., “Air Force Rationale for Rejecting CF3I as a Halon 1301 Replacement for 

F-16 Fuel Tank Inerting,” SAF/AQRE, 12 July 2002. 

2

 Rupnik, J., Bowman, R.G., and Berrill, P., eds, “Suitability of CF3I to Replace Halon 1301 as 

the Inerting Agent in Wing Fuel Tanks on the F-16 Aircraft,” HydroGeoLogic, Inc., Herndon, 

VA, 2002. 

3

 Grosshandler, W.L.; Gann, R.G.; Pitts, W.M., eds., “Evaluation of Alternative In-Flight Fire 

Suppressants for Full-Scale Testing in Simulated Aircraft Engine Nacelles and Dry Bays,” 

Chapters 6, 7, and 8, NIST Special Publication 861, pp. 643-763, National Institute of Standards 

and Technology, Gaithersburg, MD, 1994. 

4

 Gann, R.G. ed., “Fire Suppression System Performance of Alternative Agents in Aircraft 

Engine and Dry Bay Laboratory Simulations,” Volume, Chapters 5, 6, and 7, Special Publication 

890, pp. 121-404, National Institute of Standards and Technology, Gaithersburg, MD, 1995. 

5

 Price, H.M., “Compatibility of F-16 Integral Fuel Tank Materials with CF3I,” Report MPLR2686, Lockheed Martin Tactical Aircraft System, October 4, 1999. 

6

 Dante, J.F., Air Force Research Laboratory Memo to Lockheed Martin, 18 Aug 2000. 

7

 Stoudt, M.R.; Fink, J.L.; Dante, J.F.; and Ricker, R.E., (Compatibility with Metals” in Gann, 

R.G. ed., “Fire Suppression System Performance of Alternative Agents in Aircraft Engine and 

Dry Bay Laboratory Simulations,” Volume, Chapters 5, 6, and 7, Special Publication 890, pp. 

121-404, National Institute of Standards and Technology, Gaithersburg, MD, 1995. 

12
 8 Yang, J.C.; Manzello, S.L.; Nyden, M.R.; Connaghan, M.D., “Discharge of CF3I in a Cold 

Simulated Aircraft Engine Nacelle,” National Institute of Standards and Technology, in 

preparation, 2002. 

9

 Duan, Y-Y., Zhu, M-S., and Han, L-Z., Experimental Vapor Pressure Data and a Vapor 

Pressure Equation for trifluoroiodomethane (CF3I),” Fluid Phase Equilibria 121, 227-234 

(1996). 

10 Dodd, D.E. and Vinegar, A., “Cardiac Sensitization Testing of the Halon Replacement 

Candidates Trifluoroiodomethane (CF3I) and 1,1,2,2,3,3,3-Heptafluoro-1-iodopropane (C3F7 I),” 

Drug and Chemical Toxicology 21(2), 137-149, (1998). 

11 Vinegar, A.; Jepson, G.W.; Hammann, S.J.; Harper, G.; Dierdorf, D.S.; Overton, J.H.; 

“Simulated Blood Levels of CF3I in Personnel Exposed During Its Release from an F-15 Jet 

Engine Nacelle and During Intentional Inhalation,” American Industrial Hygiene Association 

Journal, 60: 403-408, 1999. 

12 Solomon, S.; Burkholder, J.B.; Ravishankara, A.R.; and Garcia, R.R.; “Ozone Depletion and 

Global Warming Potentials of CF3I,” J. Geophys. Res. 99, 20929-20935, (1994). 

13 Connell, P.S.; Kinnison, D.E.; Bergmann, D.J.; Patten, K.O.; Wuebbles, D.J.; Daniel, R.G.; 

Williamson, C.K.; Miziolek, A.W.; Huie, R.E.; “Environmental Aspects of Halon Replacements: 

Considerations for Advanced Agents and the Ozone Depletion Potential of CF3I,” Proceedings 

of the 1996 Halon Options Technical Working Conference, pp. 585-598, Albuquerque, NM, 

1996. 

14 Solomon, S., and D. L. Albritton, “Time-dependent Ozone Depletion Potentials for Short- and 

Long-term Forecasts,” Nature 357, 33-37, (7 May, 1992). 

15 Wuebbles, D., and Patten, K., University of Illinois, private communication, 2002. 

13