I , 

ASSESSMENT OF FIREFIGHTER EXPOSURE TO HCFC-123 

DURING FIRE EXTINGUISHER USE IN AIRCRAFf HANGARS 

Submitted to: 

American Padfic Corporation 

3770 Howard Hughes Parkway 

Las Vegas, Nevada 89101 

MERiDIAN RFSEARCII, hVC. 

May 24, 1993 
ASSESSMENT OF FIREF1GHTER EXPOSURE TO HCFC-123 

DURING FIRE EXTINGUISHER USE IN AIRCRAFT HANGARS 

Submitted to: 

American Pacific Corporation 

3770 Howard Hughes Parkway 

Las Vegas, Nevada 89101 

Submitted by: 

Meridian Research, Inc. 

1010 Wayne Avenue, Suite 1220 

Silver Spring, MD 20910 

May 24, 1993 
ASSESSMENT OF F1REFIGHTER EXPOSURE TO HCFC-123 

DURING FIRE EXTINGUISHER USE IN AIRCRAFT HANGARS 

I. PURPOSE 

Under Title IV, Section 612 of the Clean Air Act Amendments (CAAA) of 1990, 

the Environmental Protection Agency (EPA) is required to develop regulations 

governing the use of substitute materials for ozone-depleting chlorofluorocarbons 

(CFC's) and halons. The statute requires the replacement, to the maximum extent 

practicable, of these materials with alternatives that reduce the overall risks to humans 

and the environment. In order to make these determinations, EPA must evaluate the 

risks potentially associated with exposures of consumers, workers, and the general 

population to alternative compounds. 

One such alternative to the use of halon flre extinguishing agent is Halotron I, 

which contains HCFC-123 (2.2-dichloro-1,1,1-trifluoroethane) as the primary active 

ingredient. Recently, concerns regarding the potential toxicity of HCFC-123 and 

associated risks to exposed workers have arisen from the results of animal toxicity 

testing; in response to these fmdings, the El. duPont deNemours Co., the sole U.S. 

manufacturer of HCFC-123, recommended that exposures to HCFC-123 not exceed 

10 parts per million (ppm) parts of air as an 8-hour time-weighted average (TWA), 1,000 

ppm for 30-minute exposures, or 2,500 ppm for 1 minute exposures. 

In a previous evaluation performed for EPA, Meridian Research used a 

generalized air dilution model to estimate the potential exposure of firefighters to 

HCFC-123 that may result from using Halotron I extinguishers in aircraft hangars. The 

results from the model suggested that peak exposures could be as much as 30 times 

above the 1,000 ppm short-term limit for HCFC-123; however, predicted exposures 

obtained from the model were associated with a high degree of uncertainty due to the 

large range in plausible values for several key variables used in the model. To obtain 

better information on the potential risks to frreflghter associated with exposure to 

HCFC-123, Meridian conducted an industrial hygiene survey to measure actual exposures 

1 
that result from using Halotron I in indoor fire situations. In addition, the performance 

of the model previously used by Meridian was evaluated with respect to the exposure 

monitoring results obtained. The survey was conducted on January 6 and 7, 1993, and 

was snonsored bv American Pacific Corporation, which manufactures Halotron I. ----,.--- ~ ..... -

II. DESCRIPTION OF THE FACILITY AND METHODS USED 

The survey was conducted in a typical military aircraft hangar located at the 

Charleston Air Force Base in South Carolina. The hangar measured approximately 210 

feet long by 90 feet wide by 50 feet high at its peak, and was vacant at the time of the 

survey. According to Air Force personnel, this hangar is considered to be small 

compared to most installations world-wide. The hangar was equipped with a series of 

manually operated bay doors that permitted the hangar to be opened on one side along 

its entire length. Smaller bay doors were present along the opposite side; these were 

partially open during all tests conducted. There were no forced ventilation systems 

available for use in this hangar. 

A trained frrefighter operated all frre extinguisher equipment, which consisted of 

hand-held 20-pound units and portable 150-pound units filled to capacity with the 

Halotron I agent. During the tests, the frrefighter wore a complete ensemble of 

protective gear, including a self-contained breathing apparatus (SCBA). The extinguisher 

units were completely discharged for each test. A series of five tests were conducted 

over a two-day period. On the frrst day, a 20-pound unit and a 150-pound unit were 

discharged with the large bay doors closed. On the second day, a 20-pound unit was 

tested with the large bay doors closed, after which the large bay doors were open while 

conducting one test each with a 150- and 20-pound unit. Typically, the bay doors will be 

open when aircraft and personnel are working in the hangar. 

Exposure of the frrefighter to HCFC-123 was evaluated by collecting air samples 

in 1-liter Tedlar bags during discharge of each extinguisher unit." A standard sampling 

cassette holder equipped with a half cassette was attached near the frrefighter's breathing 

zone and outside of the protective hood. Tygon tubing was used to connect the cassette 

holder to the air inlet of an SKC Model 224 personal sampling pump, and from the 

2 
exhaust port of the pump to the Tedlar bag. The flow rate of the pump was set between 

0.75 liter per minute and 1.75 liters per minute, depending on the expected duration of 

Halotron I discharge. Collection of air was ceased as soon as possible after completion 

To evaluate potential exposures of personnel entering the hangar after a flre 

event, and to provide data that could be used to evaluate the performance of the 

theoretical model, a series of stationary area sampling devices were set up at various 

points along the length of the hangar. The configuration of the hangar and approximate 

location of the flreflghter and area samples are shown in Figure 1. Area samples were 

collected on SKC 50/100 mg charcoal tubes using a flow rate of 50 eel min; for each 

sample, two charcoal tubes were used in series to minimize sample loss due to 

breakthrough. With the exception of one test, area samples were collected over 30-

minute periods; a 15-minute sampling duration at twice the normal flow rate was used 

for the test of the 20-pound unit with the large bay doors open. The limit of detection 

for HCFC-123 using these methods was 1 ppm. 

A portable MIRAN-1BX Ambient Air Analyzer (Foxboro) was used to obtain 

periodic real-time measurements of HCFC-123 concentrations during each test. This 

instrument was pre-calibrated for HCFC-123, and had a working range of 1.9 to 1,000 

ppm. The MIRAN was used to verify that concentrations of HCFC-123 at various 

locations in the hangar had fallen to below detectable levels before starting a new test. 

Results obtained from the Miran will differ from those obtained from the area samplers 

because the area samplers yield an average HCFC-123 concentration over the sampling 

period, whereas the Miran measures the HCFC-123 concentration at a given point in 

time. 

The Tedlar bag and charcoal tube samples were analyzed using gas 

chromatography by a laboratory accredited by the American Industrial Hygiene 

Association (Gascoyne Laboratories, Inc., Baltimore, Maryland). Charcoal tube samples 

were desorbed with carbon disulflde prior to analysis. For the Tedlar bag samples, the 

column used by Gascoyne was 5 percent Krytrox 143 AC on Graphpac GB with a 60/80 

mesh that was 10 feet by 1/8 inch SS and had a flow of 30 ml/ minute (helium). The 

3 
following GC conditions were noted: injection temperature 22SOC; detector temperature 

250'C; a run time of 16 minutes; and an oven temperature of 70'C (isothermal). A 

Perkins-Elmer gas chromatograph with a sigma lB analyzer equipped with a flame 

ionization detector (FID) and a sigma lB integrator/ GC control was used for analysis. 

Injections were done with a gas-tight syringe. 

To examine the stability of HCFC-123 in Tedlar bags, Gascoyne performed a 

decay rate study using 10, 100, and 1000 ppm concentrations of HCFC-123 spiked into 

Tedlar bags. The spiked samples were held at room temperature and alloquats were 

withdrawn for analysis at various intervals over a 3-day period. The results of this decay 

rate study are shown in Attachment 1, and demonstrate that there was no significant 

sample loss over the 3-day test period. 

m. RESULTS AND DISCUSSION 

Tables 1 and 2 show the results obtained from the MIRAN analyzer and charcoal 

tubes, respectively. HCFC-123 concentrations exceeded 1,000 ppm only following the 

test of the 150-pound unit with the large bay doors closed; concentrations fell to below 

1,000 ppm within 30 minutes after agent discharge. Natural air ventilation provided by 

the two small, partially open bay doors was sufficient to reduce HCFC-123 

concentrations to below 10 ppm within two to three hours. 

Table 3 provides the results from personal breathing zone air sampling conducted 

using the Tedlar bags. Exposure of the firefighter to HCFC-123 during agent discharge 

was well below 1,000 ppm for all test trials. On the second day of testing, there was an 

appreciable air flow from the smaller bay doors towards the large bay doors; this caused 

the visible cloud of extinguishant material to move directly towards the flreflghter when 

the large bay doors were open. As a result, the exposure of the firefighter to HCFC-123 

was generally higher during the two tests conducted with the large bay doors open. 

The measured exposure of the firefighter to HCFC-123 was substantially below 

the values previously predicted by Meridian using the general air dilution model. The 

model that was used in the prior analysis for EPA is derived from a differential material 

balance that, when integrated, provides a basis for relating air concentration of 

4 
contaminant to the generation and removal rates of a contaminant. Starting with a 

fundamental material balance equation, assuming no contaminant is in the supply air: 

Rate of Accumulation = Rate of Generation - Rate of Removal 

VdC=Gdt-Q'Cdt (Equation 3-1) 

Where: 

C = Concentration of gas or vapor at time t 

G = Rate of generation of the contaminant ( cfm) 

Q' = Effective rate of ventilation that is corrected for incomplete mixing (cfm) 

(a mixing factor of 05 is assumed, which is multiplied by the actual 

ventilation rate to yield Q ') 

V = Volume of room or enclosure (ff) 

Rearranging, integrating, and further simplifying the material balance equation 

yields the fmal equation used to estimate contaminant concentration during the release 

of the contaminant, assuming that there is no initial concentration at time = 0: 

(Equation3-5) 

When the release of contaminant stops, the air concentration declines as the 

contaminant is diluted by fresh air. That is: 

Rate of Accumulation = Rate of Removal 

VdC=-Q'Cdt (Equation3-6) 

Rearranging, integrating, and further simplifying this material balance equation 

results in the equation used to estimate contaminant concentration after a given period 

of dilution: 

5 
(Equation 3-7) 

(Equation 3-8) 

(Equation 3-9) 

_.2:(t-t] C =C e v -~ '· 

2 1 (Equation 3-10) 

The area sampling data obtained during this survey now provides the information 

needed to explore the reasons underlying the model's tendency to overestimate exposures 

of frrefighters using Halotron I in large, enclosed areas. To perform this analysis, 

Meridian defmed the boundaries of an imaginary ''box" in which the frrefighter was 

stationed during the discharge of the Halotron I agent. The boundaries of the floor area 

of the box are defined by the locations of the area sampling stations on either side of the 

firefighter, i.e., the area samplers at locations 1 and 2 in Figure 1. The forward end of 

the box is defmed by the hangar wall, and the back end of the box is defined by the 

frrefighter's location during agent discharge. The floor area for this defined space is 

approximately 3,800 ft_l. Meridian also assumed an effective height of the imaginary box 

of 12 feet, the same as assumed in the prior analysis conducted for EPA; thus, the total 

volume of the imaginary box is about 45,000 ff. Using the model described above and 

the volume of the defined box, Meridian estimated the HCFC-123 concentrations that 

are predicted to result at air exchange rates of 3, 10, or 30 air changes per hour (ACH) 

(air exchange rates were selected to be consistent with the previous analysis conducted 

for EPA). The results of the model runs are compared to the average HCFC-123 

concentrations measured at area sample locations 1 and 2; Table 4 contains the results 

of the model runs as compared to actual measured HCFC-123 concentrations. 

Under the conditions of these tests, the predictive model failed to adequately 

describe the actual concentrations of HCFC-123 found in the immediate vicinity of agent 

discharge. At lower air exchange rates (i.e., 3 and 10 ACH), predicted HCFC-123 

6 
concentrations were substantially higher than actual measured concentrations. At an air 

exchange rate of 30 ACH, the concentration predicted to result shortly after agent 

discharge is within a factor of two times the measured concentration; however, the model 

predicts that the decline in HCFC-123 concentration is much faster than the decline 

measured by the area samplers. Thus, the actual average air exchange rate in this area 

of the hangar appeared to be well below 30 ACH. The comparison between predicted 

and measured concentrations is the same for both trials involving the 20-pound and 150-

pound units. 

The inability of the model to accurately predict HCFC-123 concentrations under 

the test conditions most likely reflects a violation of the basic assumption underlying the 

model that a contaminant, once released, immediately fills the space defined by the box. 

The violation of this assumption was visually apparent during the test, in which a portion 

of the visible cloud of extinguishing agent could be observed moving away outside of the 

region of the imaginary box in which the firefighter was stationed. In addition, the 

extinguishing agent is forcefully discharged away from the frrefighter at a distance of 

about 10 feet; thus, a large portion of the material never reaches the immediate vicinity 

of the firefighter, resulting in exposures that are lower than predicted by the model. 

Thus, the heterogeneous dispersion of the extinguishing agent rendered the boundary 

definition of the imaginary box inaccurate. The results of the monitoring survey and the 

comparative analysis described above indicate that the model previously used by 

Meridian is not suitable for predicting exposures of frrefighters using extinguishing agents 

in relatively large spaces. 

Comparison of the monitoring results with DuPont's allowable exposure limits of 

1,000 ppm for 30 minutes and 2,500 ppm for one minute indicates that, under the 

conditions of these tests, use of Halotron I extinguishing agent in aircraft hangars 

appears to be safe from the perspective of worker health. 

7 
Figure 1. (~onfi_guration ofHan~ar and Location of 

]Firefighter and Area 3amplers 

······················· 

l 

Office 1 

j 

4 

Partially Open 

Bay Boor 

Half-Open 

Bay Door 

3 2 

Closed 

Bay Door 

I Direction of 

Agent Dischargl 

~· 

~ ~/ FF 

Location of Area Sampling Pumps 

Large Bay Doors 
Table L HCFC-123 Concentrations Measured with the Miran Analyzer 

Average Concentration (QQm) in Location a: 

Time After Discharge 

Discharge (min) 1 Point 2 3 

Test of 20-4b. unit, Day 1 

15 140 21~50 46 19 

40 18 20 13 13 

90 4.5 4.0 3.1 4.0 

120 2.5 3.1 2.0 2.1 

Test of 15D-lb. unit, Day 1 

30 700 1000 700 700 

60 145 180 

120 9 10 11 9.5 

170 3.2 4.4 5.0 4.0 

Test of 20-4b. unit, Day 2 

5 20~00 400-500 360 10Q-500 

20 40 39 34 28 

45 6.5 6.7 6.6 6 

80 <1.9 <1.9 <1.9 <1.9 

Test of 150-4b. unit, Day 2 b 

5 100 120 210 150 

15 15 16 17 19 

30 1.3 2.0 2.8 3.2 

Test of 20-4b. unit, Day 2 b 

5 41 45 45 15-20 

15 4.2 4.3 5.3 5.2 

a Numerical designations correspond to locations shown in Figure 1. 

bLarge bay doors were open for tests conducted on Day 2. 

4 

29 

12 

3.7 

2.1 

650 

180 

7 

2.5 

630 

37 

3.5 

<1.9 

23Q-250 

35 

3.6 

4-6 

5.6 
Table 4. Com pari son of Measured and Predicted HCFC-123 Concentrations 

Predicted HCFC-123 Cooncentration 

Time After Measured HCFC-123 at Designated Air Exchange Rate (ACH) 

Discharge (min) Concentration (ppm) 3 10 30 

Test of 2o-l.b. unit, Day 1 

<HO 68.5 656.0 321.0 983 

3o-60 13.8 307.0 25.8 .05 

60-90 5.6 144.0 2.1 <01 

90-120 23 67.7 0.2 <01 

12Q-150 1.1 31.8 <.01 <01 

Test of 15o-l.b. unit, Day 1 

<HO 471.2 4,913.0 2,408.0 737.0 

3o-60 245.4 2,306.0 193.0 0.4 

60-90 73.7 1,082.0 15.5 <01 

90-120 27.1 508.0 13 <.01 

12G-150 9.45 238.0 0.1 <01 

15Q-180 6.85 112.0 <01 <01 

1? 
ATI'ACHMENT I 

@a:s.cn~n.e 'lfiahnra±uri.e:s, ~n.c~ · Baltimore, MD 21224 

~m©?~w~ 

{410) 633-1800 

FAX NO. 

{410) 633·6553 

{8001 GAS·COYN 

Report No. 92-10-487 Report Date: November 19, 1992 

Report To: Meridian Research Page:. 2 of 4 

Decay Rate Study of Laboratory Prepared HCFC-123 in Air Samples 

Theoretical 

Value = 8.9 ppm 

Theoretical 

Value = 89 ppm 

Theoretical 

Value = 890 ppm 

Elapsed Time 

o hours 

8 hours 

24 hours 

32 hours 

48 hours 

72 hours 

Notes: 

7.7, 7.7 76, 82 1100, 1100 

7.5, 7.5 80, 78 940, 950 

.a. o, 8.2 79, 100 1000, 1000 

8. 6' 9.5 120, 91 1000, 1000 

8.4, 8.2 84, 91 1000, 1000 

8.7, 8.0 100, 125 900, 920 

(1) Results are expressed in parts per million (ppm). 

(2) Duplicate analyses are reported for each time period. 

(3) Analysis performed with parameters outlined in method submitted 

to Gascoyne Laboratories, Inc. by Meridian Research. 

(4) All analyses were performed ± 1 hour of target analysis time. 

(5) Analyst(s): JMRfSJN; Date Test Completed: 11/06/92 

~-

William L. Lock 

Laboratory Director