United States National Risk Management

Environmental Protection Research Laboratory

Agency Research Triangle Park NC 27711

Research and Development EPA/600/SR-95/150a December 1995

Low Ozone-Depleting

Halocarbons As Total-Flood

Agents: Volume 1—Candidate

Survey

S. R. Skaggs, R. E. Tapscott, J. S. Nimitz, and T. A. Moore

Project Summary

Adequate protection of enclosed facilities against explosions and fires involving flammable gases or streaming

liquid fuels poses major safety challenges for the Alaskan North Slope petroleum industry. At present, such

facilities are protected by Halon 1301

total-flood fire suppression systems.

However, because of its impact on

stratospheric ozone, the production of

Halon 1301 was halted under international regulation on December 31, 1993.

The report describes the results of a

survey of possible low ozone-depleting

halocarbon replacements for Halon

1301 in North Slope applications. Candidate agents surveyed in this project

included perfluorocarbons, hydrofluorocarbons, and hydrochlorofluorocarbons

as well as selected hydrobromofluorocarbons, fluoroiodocarbons, haloethers,

and haloalkenes. Selection criteria used

to evaluate these candidates were

physical properties, chemical stability,

toxicity, availability, cost, materials

compatibility, cleanliness, environmental considerations, and regulatory concerns. Based on these criteria, 29

chemicals are recommended for laboratory-scale testing.

This Project Summary was developed

by EPA’s National Risk Assessment

Research Laboratory, Research Triangle

Park, NC, to announce key findings of

the research project that is fully documented in a separate report of the same

title (see Project Report ordering information at back).

Introduction

Adequate protection of enclosed facilities against explosions and fires involving

flammable gases or streaming liquid fuels

poses major safety challenges for the Alaskan North Slope petroleum industry. Facilities on the North Slope are presently

protected by Halon 1301 total-flood fire

suppression systems. However, the cessation of production of Halon 1301 as

mandated by the Montreal Protocol for

Protection of the Ozone Layer is expected

to severely limit future availability of this

chemical. The report describes the initial

effort undertaken to evaluate other families of halocarbons as substitute total-flood

fire and explosion protection agents for

North Slope petroleum production, handling, and transport facilities.

The effort was divided into two areas of

emphasis: (1) physical action agents

(PAAs) and (2) chemical action agents

(CAAs). PAAs are chemicals that extinguish fires by a variety of mechanisms

including vapor-phase heat absorption, liquid-phase heat absorption, evaporative

cooling, thermal dissociation, dilution of

fuel and oxygen, and separation of fuel

and oxygen. CAAs cause fire extinguishment primarily by removal of free radicals

that promote combustion chain reaction

mechanisms. For halocarbon agents, significant free radical removal requires the

presence of bromine or iodine in the halocarbon. In general, CAAs have higher explosion protection and fire suppression

capabilities than PAAs. However, CAAs
2

also tend to have higher toxicities, and

bromine-containing CAAs tend to have

high ozone depletion potentials. Assignment of a chemical to either the PAA or

CAA category does not imply that the

particular agent does not operate by both

mechanisms, rather that one action appears to be the predominant mode of extinguishment.

Selection of Candidates for

Laboratory-Scale Testing

Available information on the physical

properties, chemical stabilities, toxicities,

availabilities, costs, materials compatibilities, fire suppression capabilities, and

environmental considerations for approximately 650 halogenated hydrocarbons was collected and screened.

Sources for the information included the

open literature and industry contacts. The

effectiveness of an explosion or fire suppression agent depends upon agent

deliverability, heat removal capability, and

free radical reaction termination capability. Physical properties to be considered

when determining the potential of a chemical for total-flood applications include boiling point, freezing point, vapor heat

capacity, heat of vaporization, vapor pressure at room temperature, heat of reaction to form products, viscosity, and vapor

and liquid density. Some of these properties relate primarily to deliverability (e.g.,

boiling point, vapor density, viscosity, and

vapor pressure) and some to extinguishing ability (e.g., vapor heat capacity and

heat of vaporization).

Halon 1301 has a boiling point of -58°C

and is delivered as a gas in fire suppression and explosion prevention applications.

For purposes of this initial screening of

Halon 1301 alternatives, compounds having known boiling points between -150°C

and 0°C were considered acceptable.

When boiling points were not known, an

algorithm was used to predict these values and the acceptable range was extended to be -170°C to +20°C to allow for

error in the predicted values. A preliminary database survey identified 52 PAAs

and 40 CAAs with boiling points within the

desired boiling point range.

For effective heat removal, an agent

should have a high vapor heat capacity

and high heat of vaporization. Ideally, the

vapor heat capacity and heat of vaporization should be equal to or higher than

those of existing agents. However, for this

screening no agents were strictly disqualified if they did not meet these criteria. The

freezing point of the agent should preferably be below -60°C. In normal usage an

agent would not experience temperatures

below 0°C; however, cylinders of agent

being transported outdoors in wintertime

at the Alaskan North Slope could be exposed to temperatures as low as -60°C.

Of the 92 chemicals found to have boiling

points within the desired boiling point

range, all had known freezing points above

-60°C.

Since agents are often stored for long

periods before use, sometimes under extremes of temperature, agents must be

chemically stable during long-term storage. Chemical stability implies the absence

of easy decomposition pathways. Highly

fluorinated chemicals are less likely to undergo the oxidative reactions that often

destroy molecules containing carbon-tocarbon bonds. During initial screening,

agents containing particularly weak carbon-to-halogen bonds were ranked lower

than comparable agents with stronger

bonds. None of the compounds in the

preliminary list of 92 contained any particularly unstable functional groups. Therefore, chemical instability is not expected

to be a problem for any of the chemicals.

It is desirable that an alternative agent

be as nontoxic as possible. This is especially the case where the agent is to be

dispersed as a gas into a room occupied

by humans. Exposure of personnel to

agents can occur during manufacturing,

handling, system maintenance and storage, as well as during agent discharge for

fire suppression or explosion prevention.

Human and animal studies indicate several possible adverse effects of halocarbons. First, halocarbons can stimulate or

suppress the central nervous system to

produce symptoms ranging from lethargy

and unconsciousness to convulsions and

tremors. Second, halocarbons can cause

cardiac arrhythmias and can sensitize the

heart to epinephrine (adrenaline). Third,

inhalation of these chemicals can produce

bronchioconstriction, reduce pulmonary

compliance, depress respiratory volume,

reduce mean arterial blood pressure, and

produce tachycardia (rapid heartbeat).

Fourth, these agents can cause organ

damage by degradation products of metabolism. Lastly, halocarbons can produce

cancerous or mutagenic effects. Generalization of toxic effects to an entire class of

chemicals is not possible, and toxicity information on each candidate must be individually acquired in order to assess fully

its potential health hazards.

For this study, all publicly available toxicity information on the chemicals of interest was collected and evaluated. This was

accomplished by performing on-line computer searches of toxicological databases

such as Toxlit, Toxline, and Chemical Abstract Services, by manual searches, and

in certain circumstances by soliciting unpublished information from industry

sources. For many chemicals, little, if any,

toxicological information was found. For

such chemicals, toxicities were assessed

through quantitative structure-activity relationships to achieve preliminary estimates

of anesthetic potential and lethal index.

Agent cleanliness is another important

consideration for certain applications.

Cleanliness is defined as the ability of the

fire extinguishant to evaporate rapidly without leaving residue harmful to electronic

or other equipment. One of the major advantages of the halons is their cleanliness. They can be used on electronic,

electrical, or complex mechanical equipment without requiring subsequent cleanup

or causing equipment malfunction. All halocarbons with boiling points below 50°C

that do not contain high boiling impurities

are expected to be clean. Meeting the

cleanliness requirement is not expected

to be a problem for any of the agents

considered in this study.

Data on ozone depletion potentials

(ODPs), global warming potentials

(GWPs), and atmospheric lifetimes were

collected or estimated. Both ODPs and

GWPs depend in part on atmospheric lifetimes. For ODP, a longer lifetime means

that a greater proportion of the molecules

released reaches the stratosphere where

photolysis creates the chlorine or bromine

radicals that catalyze destruction of ozone.

With respect to global warming, a longer

lifetime means that the molecules are absorbing infrared radiation from the surface

of the earth and transforming it to kinetic

energy for a longer time, resulting in increased warming. Therefore, it is desirable that alternative agents have short

atmospheric lifetimes.

Conclusions

Taking all of the available and estimated

data together, the 92 chemicals initially

selected on the basis of appropriate boiling points were prioritized for further evaluation. Table 1 lists 43 of the 52 PAAs by

groups with regard to the desirability for

further testing and evaluation. Group 1

PAAs are those which are believed to

warrant testing in the laboratory. All of

these chemicals have attractive physical

properties, potentially low toxicities, acceptable environmental characteristics, and

are available for testing. Of these chemicals, all have been tested in a laboratory

cup burner apparatus and found to exhibit

extinguishing concentrations ranging from

6 to 12% by volume. Group 2 PAAs have

attractive physical properties, predicted
3

flame extinguishment concentrations ranging between 8 and 11%, and are commercially available. Group 3 chemicals are

generally not available; however, several

from this group look attractive. For example, HFC-227ca appears to have a relatively low toxicity based on limited acute

data, its boiling and freezing points are

known and acceptable, and it has structural features that presumably could enhance its extinguishment capabilities.

Other PAAs were rejected as candidates

either because of insufficient data to make

a decision or, as in the case of HCFC-31,

because the chemical had known unacceptable toxic characteristics.

Table 2 groups the CAAs into those

recommended for laboratory-scale testing,

those that are not commercially available,

and those that are considered unacceptable. Although brominated compounds

exhibit superior fire suppression and explosion prevention effectiveness, regulations fostered by the Montreal Protocol

prohibit future production of these chemicals. Therefore, it is recommended that

such chemicals not be investigated further.

Several fluoroiodocarbons were identified that exhibit superior flame suppression capabilities although the higher

molecular weight compounds do not appear to perform as well as expected for

explosion prevention. The toxicity of the

perfluoroiodocarbons may be sufficiently

low to allow the use of these chemicals as

total-flood agents. For those chemicals with

boiling points above 20-30°C, an alternate

means of dispersal would most likely be

required. The presence of the iodine atom

in the molecule is presumed to subject

the compound to rapid photolytic breakdown in the lower atmosphere so that the

compound would not pose a threat from a

global warming or ozone depletion standpoint.

A number of halogenated ethers have

been investigated as possible halon replacement agents. These include both brominated and nonbrominated compounds.

Nonbrominated fluoroethers perform as

physical action agents similar to hydrofluorocarbons, but uncertainty still remains

as to whether the addition of the oxygen

atom will reduce the atmospheric lifetime

enough to limit the ODP to acceptable

levels. Finally, little toxicological information exists on the haloether candidates.

Consequently, a high priority is not assigned to the haloethers.

Table 1. Candidate Group List of Physical Action Agents

Halocarbon

Group Number Formula Comment

1 14 CF4 toxicity expected to be low

Recommended 22 CHClF2 low toxicity

for 23 CHF3 long atmospheric lifetime

Lab-testing 32 CH2F2 flammable

116 CF3CF3 low toxicity

124 CHClFCF3 low toxicity

125 CHF2CF3 limited availability

134a CH2FCF3 low toxicity

142b CClF2CH3 flammable

143a CH3CF3 flammable

152a CHF2CH3 very low toxicity

218 CF3CF2CF3 low toxicity

3-1-10 C4F10 toxicity expected to be low

C318 C4F8 decomposition products may be toxic

2 124a CHF2CClF2 unknown tox but expected to be low

Recommended 134 CHF2CHF2 unknown tox but expected to be low

for 227ea CF3CHFCF3 unknown tox but expected to be low

Lab-testing 236fa CF3CH2CF3 acute toxicity known

245cb CF3CF2CH3 unknown tox but expected to be low

3 142a CHClFCH2F no data

Unavailable 216 CF2CF2CF2 no data

Commercially 226ba CF3CClFCHF2 no data

227ca CF3CF2CF2H acute toxicity known

234 CF2CF2CH2 no data

235cc CH2FCF2CClF2 acute toxicity known

235da CF3CHClCHF2 anesthetic at low concentrations

235ca CHF2CF2CHClF anesthetic at low concentrations

236cb CH2FCF2CF3 no data

244db CF3CHClCH2F no data

244bb CF3CClFCH3 anesthetic at low concentrations

244ca CHF2CF2CH2Cl no data

244fb CClF2CH2CHF2 acute toxicity known

244cb CH2FCF2CHClF no data

244da CHF2CHClCHF2 anesthetic at low concentrations

245eb CF3CHFCH2F no data

245ea CHF2CHFCHF2 no data

245ca CHF2CHF2CH2F no data

254eb CF3CHFCH3 probably flammable, no data

254ea CHF2CHFCH2F probably flammable, no data

254fa CHF2CH2CHF2 probably flammable, no data

254ca CH2CF2CH2F probably flammable, no data

254cb CHF2CF2CH3 probably flammable, no data

4 31 CH2ClF cancer-causing in lab animals

Unacceptable
4

Table 2. Candidate Group List of Chemical Action Agents

Group Name Formula Comment

1 Trifluoroiodomethane CF3I toxic?

Recommended Pentafluoroiodoethane CF3CF2I toxic?

for Perfluoro-n-propyl iodide CF3CF2CF2I toxic?

Lab-testing Perfluoro-n-butyl iodide CF3CF2CF2CF2I toxic?

Perfluoro-n-hexyl iodide CF3(CF2)4CF2I toxic?

4-Bromo-3,3,4,4-tetrafluoro-1-butene CH2=CHCF2CBrF2 toxic?

2 Perfluoro-n-octyl iodide CF3(CF2)6CF2I high BP*

Recommended 1,1,2,2-Tetrafluoro-dimethyl ether CHF2OCHF2 need data

for 1,1,2,2-Tetrafluoroethyl difluoromethyl ether CHF2OCF2CHF2 need data

Lab-testing 1,1,1-Trifluoroethyl difluoromethyl ether CF3CH2OCHF2 need data

3 Difluoroiodomethane CHF2I no data

Unavailable Fluoroiodomethane CH2FI carcinogenic?

Commercially Perfluorodimethyl ether CF3OCF3 long life?

Methyl trifluoromethyl ether CH3OCF3 expensive, flammable

Difluoromethyl fluoromethyl ether CHF2OCH2F no data

Trifluoromethyl difluoromethyl ether CF3OCHF2 no data

Trifluoromethyl pentafluoroethyl ether CF3OCF2CHF2 not available

Perfluorooxetane -CF2CF2CF2O- long life

1,1,1-trifluoroisopropyl trifluoromethyl ether CF3(CH3)CHOCF3 not available

Perfluorodimethoxymethane CF3OCF2OCF3 no data

Difluoromethyl bromodifluoromethyl ether CHF2OCBrF2 no data

Trifluoromethyl bromodifluoromethyl ether CF3OCBrF2 no data

Difluoromethyl bromotetrafluoroethyl ether CHF2OCF2CBrF2 need data

Methyl bromodifluoromethyl ether CH3OCBrF2 no data

3-Bromo-3,3-difluoropropene CH2=CHCBrF2 mutagenic

3-(Bromodifluoromethyl)-3,4,4,4-tetrafluoro-1-butene CH2=CHC(CBrF2)FCF3 not available

1-Bromo-3,3,3-trifluoro-1-propene BrCH=CHCF3 mutagenic?

2,3-Dibromo-3,3-difluoro-1-propene CH2=CBrCBrF2 mutagenic

4-Bromo-3-chloro-3,4,4-trifluoro-1-butene CH2=CHCClFCBrF2 mutagenic

3-Bromo-1,1,3,3-tetrafluoro-1-propene CF2=CHCBrF2 highly toxic?

1,2-Dibromo-3,3,3-trifluoro-1-propene BrCH=CBrCF3 mutagenic?

4 Perfluoroisopropyl iodide CF3CFICF3 too toxic

Unacceptable 1,1-Difluoroethyl fluoromethyl ether CHF2CH2OCH2F flammable? available?

Dibromofluoromethane CHBr2F high ODP**

1,2-Dibromo-1,1,2-trfluoroethane CBrF2CHBrF highly toxic, ODP

2,2-Dibromo-1,1,1-trifluoroethane CHBr2CF3 highly toxic, ODP

2,3-Dibromo-1,1,1-trifluoropropane CF3CHBrCH2Br highly toxic, ODP

Bromodifluoromethane CHBrF2 high ODP

2-Bromo-1,1,1,2-tetrafluoroethane CF3CHBrF high ODP

* BP = Boiling point.

** ODP = Ozone depletion potential.

A survey of the toxicological aspects of

bromofluoroalkenes reveals that few of

these chemicals have sufficiently low toxicities to allow their use as halon replacement agents. Many of the 2- and 3-carbon

candidates are most likely carcinogenic.

Only haloalkenes with 4 or more carbons

will possibly be nonmutagenic and noncarcinogenic. The molecular weights of

the 4 or more carbon haloalkenes are

ranked relatively high compared to Halon

1301, which will reduce the apparent effectiveness if expressed on a weight

equivalency basis.
5

Official Business

Penalty for Private Use

$300

EPA/600/SR-95/150a

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

S. R. Skaggs, R. E. Tapscott, J. S. Nimitz, and T. A. Moore are with the University

of New Mexico, Albuquerque, NM 87131-1376.

N. Dean Smith is the EPA Project Officer (see below).

The complete report, entitled "Low Ozone-Depleting Halocarbons As Total-Flood

Agents: Volume 1—Candidate Survey," (Order No. PB96-109061; Cost: $27.00,

subject to change) will be available only from

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Telephone: 703-487-4650

The EPA Project Officer can be contacted at

National Risk Management Research Laboratory

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

United States

Environmental Protection Agency

National Risk Management

Research Laboratory (G-72)

Cincinnati, OH 45268