A Continuation of Thermal Decomposition Product Testing With C6 F-ketone, 

Increased Concentrations 

Benjamin D. Ditch, Paul E. Rivers, Scott D. Thomas 

3M Specialty Materials Division 

ABSTRACT 

C6 F-ketone is effective as a halon alternative for total flooding applications. As with 

other halon alternatives, exposure to fire causes the agent to decompose thermally into 

acid gas. Small-scale testing has been conducted utilizing on-line FTIR analysis to 

quantify the concentrations of thermal decomposition products (TDP). Agent 

concentrations equal to the minimum extinguishment value as well as that value plus a 

20% safety factor were used. C6 F-ketone was found to be, in terms of TDP, directly 

comparable to other commercially available halon alternatives. 

Further testing in 3M’s 1.28-m3

 enclosure includes increased agent concentrations of that 

initial minimum value plus 40% and 60%. The three variables in the test matrix are, fire 

size, discharge time, and agent concentration. TDP are quantified using on-line FTIR 

analysis. Data are compared with other commercially available halon alternatives 

previously tested. 

INTRODUCTION 

The need to find a sustainable alternative to halons is ever increasing. Commercially 

known as 3MTM NovecTM 1230 Fire Protection Fluid, C6 F-ketone has proven to be 

effective for both total flooding and streaming applications. 

In order to design any fire protection system properly it is important to investigate all the 

possible hazards associated with that system. Issues involving interaction of agent with 

flame front are particularly important. The thermal decomposition products (TDP) of 

main concern, resulting from the exposure of a halon alternative to fire, are hydrogen 

fluoride (HF) and carbonyl fluoride (COF2). The effects of exposure to these 

compounds, mainly HF, have been well documented [1,2]. 

The three key factors affecting thermal decomposition production are the fire size-toroom volume ratio, the agent volumetric concentration, and the discharge time [3,4]. 

Previous testing has found a point of diminishing returns where further increases in agent 

concentration yield negligible reductions in TDP [5,6]. 

METHODOLOGY 

TEST ENCLOSURE 

Small-scale tests were conducted in 3M’s ‘box’ [4]. This provides a 1.28-m3

 (45-ft3) 

total floodable volume, 0.91x0.91x1.7-m3

 (3x3x5-ft3). The box is instrumented with 

pressure transducers, for cylinder and discharge pressure, and thermocouples, for 

enclosure and agent temperatures. A complete schematic of the box is seen in Figures 1a 

and 1b. 
CC

P F 

3’-0”

SP T

 

PT

PT

P

T 

T – Thermocouple

P – Pressure

Transducer

C – Agent Cylinder 

SP – Sample Port

F – Fan 

B – Baffle

N – Nozzle

NT 

8”

3’-0”

DOOR 

DOOR

T

AFP T – Thermocouple

P – Pressure 

ransducer 

C – gent Cylinder

SP – Sampling Port

P

T 

N

T 

T

A

Fan 

T- Thermocouple

P- Pressure 

 Transducer

C- Agent Cylinder

SP- Sampling Port

AFP- Air Flow Port

F- Fan 

B- Baffle 

N- Nozzle 

AFP – Air Flow Port 

F – 

5’-0”

T 

P 

3’-0” 

T

T

T

T

C

SP

SP

SP

AFP F 

 Figure 1a, Side View Figure 1b, Top View 

AGENT CONCENTRATION CALCULATIONS 

An update from previously reported agent concentrations is necessary [4]. Original agent 

concentrations were based on ideal gas law calculations for agent specific volume. This 

resulted in agent concentrations that vary slightly from those found using experimental 

data for C6 F-ketone, Table 1. It is important to note that these do not affect the original

quantities (mass) of agent used, only the corresponding concentrations (% v/v) are

represented. 

Table 1, Agent Concentration Calculations 

Agent 

(% v/v)

Ideal 

Calculations 

(% v/v)

Corrected 

Calculations 

(% v/v)

Extinguishing* 4.86 4.56

Extinguishing+20 5.83 5.47

Extinguishing+40 6.81 6.38

Extinguishing+60 7.77 7.29

*C6 F-ketone at initial n-heptane extinguishing value 

Ideal Gas Law s-Value

s = 0.071 + 0.0003T 

PRSV EOS* s-Value

s = 0.0664 + 0.000274T 

*Peng-Robinson-Stryjek-Vera 

Equation of State

Increased agent concentrations were chosen as extinguishing + 40% and extinguishing +

60%. In accordance with the procedures for measuring extinguishment for n-heptane in 

NFPA 2001, the initial total volumetric agent concentration was determined as the cupburner minimum extinguishing concentration for heptane, as established by a recognized 

testing lab. Agent mass required to produce the desired agent concentrations in the box

were calculated as follows: 





 





− = C

C

s

V W

100

where, W is the mass of the agent in lb (kg), V is the enclosure volume in ft

3

 (m3), C is

the agent design concentration (% v/v), and s is the agent specific volume at 1 atm. and 

ambient temperature [7]. 

2 
DISCHARGE TIME 

Discharge times of 3 s, 9 s, and 20+s were chosen for direct comparison with previous 

testing done [3,4,5,6]. Discharge time is controlled by the flow rate (orifice size) of the 

discharge nozzle. Initial testing was conducted to determine which nozzles were needed 

to produce the desired discharge time; the results of those tests are presented in Table 2. 

Table 2, Nozzle Discharge Times 

Agent Discharge Time

Agent Concentration 3 Seconds 9 Seconds 20+ Seconds 

n-heptane extinguishing 

+ 40% (6.4%) 

Bete 

Company 

NF3000 

Spraying 

Systems 

TP8007 

Bete 

Company 

NF0300 

n-heptane extinguishing 

+ 60% (7.3%) 

Spraying 

Systems 

TP8040 

Spraying 

Systems 

TP8008 

Spraying 

Systems 

TP8004 

FIRE SIZE

The four different fires sizes used in this study were chosen to compare with previous 

work [3,4,5,6]. A cone calorimeter was used to determine the heat release rates of the 

four square pans, which measure, 2-cm (0.75-in), 4.5-cm (1.75-in), 7-cm (2.75-in), and 

9.5-cm (3.75-in). The corresponding heat release rates for these pans when filled with

heptane are, 0.1 kW, 0.6 kW, 1.7 kW, and 3.7 kW, respectively. For each test, the pans 

were filled to the top with fresh heptane immediately before the test. Fresh heptane was

used for each test. 

FTIR ANALYSIS PROCEDURE AND SETUP 

Two MIDAC I-2000 Series Model FTIR spectrometers were used for this study. Each 

spectrometer was configured with a ZnSe beam splitter and a mercury cadmium telluride

(MCT) detector. A 0.5-cm, unheated stainless-steel gas cell utilizing sulfur hexafluoride 

(SF6) as a diluent was used to acquire C6 F-ketone concentration data. TDP 

concentrations, which are orders of magnitude less than C6 F-ketone concentrations, were

acquired using an undiluted 10-cm, unheated, stainless steel gas cell. The spectrometers

had an ultimate resolution of 0.5 cm-1 with triangular apodization. Sample gas extraction 

was accomplished with 110V gas sampling pumps. Portable computers were used for 

data acquisition. 

The extractive gas sampling system used for the enclosure testing consisted of 

approximately 8-ft of 1⁄4”-dia PTFE tubing leading into the gas cells. Each spectrometer 

and its sampling system were operated independently. Samples were continuously 

pumped through the sample line and the gas cells at a flow rate of 1 and 2 lpm for the 

0.5-cm and 10-cm gas cells, respectively. Flows were verified on site using a Dry Cal

flow meter. FTIR sampling was initiated when the fuel was ignited. After

extinguishment (5-20s), the enclosure remained sealed and was monitored until HF levels 

reached a maximum concentration and slowly began receding. The TDP and C6 F-ketone

concentrations in the enclosure were checked for residual quantities before each test. 

3 
TEST PROCEDURE 

Immediately before each test began the test pan was filled to the top with heptane. The 

test began when the fuel was ignited, at which time the access door was sealed and the 

FTIR machines were turned on. The 60-s pre-burn occurred with both the box inlet and 

outlet valves open, minimizing combustion product buildup and oxygen depletion. The 

valves were then closed, and 5 seconds later the agent was discharged. After

extinguishment, the fan inside the enclosure was turned on to mix the enclosure volume

thoroughly. The box remained sealed during the FTIR analysis cycle. 

RESULTS 

As seen in Figure 1, a decrease in the discharge time result in decreased TDP. 

Decreasing the discharge time from 9 seconds to 3 seconds results in up to a 65% 

reduction in hydrogen fluoride production (ppm). Consistent with previous results, HF

production is a monotonically increasing function of fire size [3,4,5,6,8]. This shows the 

importance of discharge time in system design. Figure 1 shows that TDP appears to level 

off as the fire size increases. This effect, previously reported by Linteris, may be 

attributed to kinetic limitations on the rate of agent consumption [9]. 

Note, at smaller fire sizes the concentration of TDP fell below the minimum detection 

limit (MDL) for the FTIR system. In these instances, a value of 0 ppm was chosen for 

comparison. For actual system design, a value equal to the MDL of the system should be 

used. That would represent a more conservative value important when safety is the major 

concern. 

Effect of C6 F-ketone Discharge Time on HF Generation

[C6 F-ketone at Extinguishing + 40% v/v]

0

500

1000

1500

2000

2500

0 0.5 1 1.5 2 2.533.5

Fire Size (kW)

Maximum HF Concentration (ppm)

25+ Second Discharge

9 Second Discharge

3 Second Discharge

4

Figure 1 

As shown previously C6 F-ketone is effective in extinguishing class A fires, Figure 2. 

The HF production from class A fires is lower than for class B fires. This is consistent 

with previous work and shows that heptane was a good choice for a “worst-case” 

4 
scenario for HF production [3,4]. The variability on the wood test is evident by the range 

in reported results.

C6 F-ketone HF Production vs Fire Size

[9-second Discharge, Extinguishing + 60% v/v]

0

200

400

600

800

1000

1200

1400

1600

0 0.5 1 1.5 2 2.5 3 3.5 4

Fire Size (kW)

Maximum HF Concentration (ppm)

Class B Fires

Class A Fires

Polyethylene

Wood

Cotton

Figure 2 

Increasing the agent concentration reduces the quantity of HF produced. A point of 

diminishing returns is reached where any further increases in agent concentration yield 

negligible reductions. This effect is irrespective of fire size and has been demonstrated 

for other agents as well. As seen in Figure 3, at extinguishing plus 40% (v/v) 

concentration HF production is at a minimum. 

Effect of Agent Concentration on TDP Generation 

[9-second Discharge]

0

500

1000

1500

2000

2500

3000

4.6 5.5 6.4 7.3

C6 F-ketone Concentration (% v/v)

Maximum HF Concentration (ppm)

3.7 kW

1.7 kW

0.6 kW

0.1 kW

Figure 3 

5 
Comparison of Commercially Available Agents

[Agents at Extinguishing + 40% v/v]

0

500

1000

1500

2000

2500

0 0.5 1 1.5 2 2.5 3 3.5 4

Fire Size (kW)

Equivalent HF Concentration (ppm)

C6 F-ketone*

HFC-227ea**

HFC-23**

*TDP analyzed using FTIR

**TDP analyzed using ISE

Figure 4 

Calculated TDP Concentrations for a 'Normal' Sized Room

[C6 F-ketone at Extinguishing + 40%]

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300

Room Size (cu. m.)

Calculated Maximum HF Concentration (ppm)

0.1 kW Fire

0.6 kW Fire

1.7 kW Fire

3.7 kW Fire

Figure 5 

In terms of HF production, C6 F-ketone in these test scenarios is directly comparable to 

other commercially available clean agents, Figure 4. Note that equivalent maximum HF 

concentrations are reported. TDP analyzed using an ion-selective electrode (ISE) only

detects the presence of hydrolysable fluoride, which is then converted to an equivalent 

HF concentration. To be consistent TDP analyzed using FTIR are also reported as 

equivalent maximum HF concentrations. Since COF2 is the only other significant 

6 
contributor to hydrolysable fluoride, equivalent HF concentrations (ppm) are determined 

as the HF concentration (ppm) plus twice the COF2 concentration (ppm). Doubling of 

the COF2 concentration is due to the effect of hydrolysis, see Equation 1. 

[Eq.1] COF2 + H2O → CO2 + 2HF

The Robens Institute indicates the highest tolerable HF concentration for a 1-min human 

exposure is 120 ppm. Figure 5 shows that when normal sized rooms and possible use 

concentrations are considered C6 F-ketone produces tolerable levels of HF. 

Discussion and Conclusion 

Test results have shown, in terms of TDP, C6 F-ketone is directly comparable to other

commercially available halon alternatives. The maximum equivalent HF concentrations

found are consistent with those for other in-kind halocarbon agents. Also, the three major 

factors affecting TDP are the fire size-to-volume ratio, discharge time, and agent 

concentration. The latter two have a direct effect on the fire extinguishment time. TDP 

is a monotonically increasing function of fire size. 

Increasing the agent concentration is an effective way to reduce TDP. However, a point 

of diminishing returns can be reached where further increases in agent concentration 

yield negligible decreases in TDP. This is consistent with previous work [5].

As indicated previously, hazards such as those present in telecommunications facilities 

often result in fire sizes less than 10 kW at detection, with detection often desired at 1 kW

[7]. When typical fire sizes and room sizes are considered, TDP concentrations fall below 

the dangerous toxic level (DTL) set by Meldrum [2]. 

Finally, through the use of effective system design, TDP concentrations can be 

maintained below dangerous levels. Among other methods, this can be accomplished 

through early fire detection, adequate agent concentrations, and system discharge time. 

An agent is only as effective as the system in which it is used. 

References

[1] A.H. Mann, “Possible Health Risks From Exposure to Hydrogen Fluoride 

Generated From the Use of Fluoride-Containing Fire Extinguishing Agents,”

Robens Institute of Industrial and Environmental Health & Safety, University of Surrey, 

Guildford, Surrey, United Kingdom, 1996 

[2] M. Meldrum, “Toxicology of Substances in Relation to Major Hazards: Hydrogen 

Fluoride,” Health and Safety Executive, ISBN 11 882100 8, 1993 

[3] M.J. Ferreira, C.P. Hanauska, M.T. Pike, “Thermal Decomposition Products 

Results Utilizing PFC-410 (3M Brand PFC-410 Clean Extinguishing Agent”, Halon 

Options Technical Working Conference, Albuquerque, NM, 1992 

[4] B.D. Ditch, P.E. Rivers, S.D. Thomas, “Thermal Decomposition Products Testing 

with L-15566,” Halon Options Technical Working Conference, Albuquerque, NM, 2001 

7 
[5] J.C. Brockway, “Recent Findings on Thermal Decomposition Products of Clean 

Extinguishing Agents,” NFPA 2001 Committee Meeting, Ft. Lauderdale, FL, 1994 

[6] M.R. Driscoll, P.E. Rivers, “The Products of Thermal Decomposition in 

Intermediate Scale Testing,” National Institute of Standards and Technology Annual 

Conference on Fire Research, Gaithersburg, MD, 1996 

[7] NFPA 2001, “Standard for Clean Agent Fire Extinguishing Systems,” 2000 Edition

[8] P.J. DiNenno, E.W. Forssell, M.J. Peatross, M. Maynard, “Evaluation of Alternative 

Agents for Halon 1301 in Total Flooding Suppression Systems – Thermal 

Decomposition Product Testing,” Halon Options Technical Working Conference, 

Albuquerque, NM, 1993 

[9] G.T. Linteris, G. Gmurczyk, “Parametric Study of Hydrogen Fluoride Formation 

In Suppressed Fires,” Halon Options Technical Working Conference, Albuquerque, 

NM, 1995 

8