United States Air and Radiation EPA430-R-00-002
Environmental Protection (6205J) February 2000
Agency www.epa.gov/ozone
c/EPA
Carbon Dioxide as a Fire Suppressant:
Examining the Risks
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Carbon Dioxide as a Fire
Suppressant:
Examining the Risks
U.S. Environmental Protection Agency
Office of Air and Radiation
Stratospheric Protection Division
February 2000
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Carbon Dioxide as a Fire Suppressant: Examining the Risks
Disclaimer
This document has been reviewed in accordance with U.S. Environmental Protection Agency
policy and approved for publication and distribution. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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Contents
Preface iv
Table of Acronyms vi
Introduction 1
Carbon Dioxide as an Extinguishing Agent 1
Extinguishing Mechanism of Carbon Dioxide 2
Extinguishing Effectiveness of Carbon Dioxide 2
Use of Carbon Dioxide Extinguishing Systems 3
Life Safety Considerations of Carbon Dioxide 5
Health Effects 5
Safety Measures 6
Design, Specification, and Component Approval 6
Installation and Testing 6
Use Controls 7
Review of Incidents (Accidents/Deaths) Involving Carbon Dioxide
as a Fire Extinguishing Agent 13
Incident Record Search 13
Library/Internet Searches Completed 13
Literature Searches 13
National Institute for Occupational Safety and Health (NIOSH)
Library Search 13
Internet Search 14
Nuclear Regulatory Commission (NRC) 14
Professional Contacts 14
Associations/Private Companies/Government Organizations/Research
Laboratories 14
Search Results 16
Examining the Risks Associated with Carbon Dioxide Extinguishing Systems 20
Conclusion and Recommendations 21
References 23
Appendix A: Death and Injury Incidence Reports Al
References for Appendix A A10
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Appendix B: Overview of Acute Health Effects Bl
References for Appendix B B7
in
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Carbon Dioxide as a Fire Suppressant: Examining the Risks
Preface
Under the Clean Air Act Amendments of 1990, the U.S. Environmental Protection Agency (EPA)
has the statutory authority to set phase-out dates for ozone-depleting substances (ODS) and to
evaluate potential risks posed by proposed ODS substitutes. Under the terms of the Montreal
Protocol on Substances that Deplete the Ozone Layer, EPA promulgated regulations to phase out
the production of Hal on 1301. In response to the halon phase-out effective January 1, 1994, the
fire protection industry has been searching for alternatives. A number of alternative technologies
have been proposed, including carbon dioxide (CO2) systems. This report was written to provide
users of total flooding halon systems, who may be unfamiliar with total flooding carbon dioxide
systems, with information regarding the potential dangers associated with carbon dioxide systems.
Appropriate precautions must be taken before switching to carbon dioxide systems and with this
report EPA attempts to raise awareness and promote the responsible use of carbon dioxide fire
suppression systems.
The authors of this report consulted with experts in the industry during the information-gathering
stage for development of the report. An early draft of the document was read by members of the
United Nations Environment Programme (UNEP) Halons Technical Options Committee (HTOC).
Many experts within the fire protection industry provided data on incidents. The penultimate
document was peer reviewed in September 1999 for its technical content by a distinguished group
of experts, including:
Rich Hansen (Test Director), United States Coast Guard - R&D Center
Matsuo Ishiyama, member of HTOC, Corporate Advisor and Auditor, Halon Recycling
and Banking Support Committee, Japan
Joseph A. Senecal, Ph.D., Director of Suppression Engineering, Kidde-Fenwal, Inc.
Charles F. Willms, P.E., Technical Director, Fire Suppression Systems Association
Thomas Wysocki, P.E., President and Senior Consultant, Guardian Services, Inc.
Roy Young, HTOC member, United Kingdom
Comments were received from all peer reviewers. Some reviewers expressed concern that the
document be written clearly enough to lay out the associated risks in a way that neither promoted
nor unduly discouraged the use of carbon dioxide-based fire extinguishing systems, and changes
were made in the introduction to address this concern. A reviewer described the document as "a
very valuable contribution to the safety subject and . . . should be used by carbon dioxide systems
providers as a positive tool to promote training, maintenance, and adherence to proven
standards." All reviewers were pleased that a report on the risks associated with carbon dioxide
systems had been prepared.
One reviewer found the report to accurately reflect current "land-based" requirements, but added
information related to the importance of training both new crew and contracted maintenance
workers in marine applications. The conclusions of the report were changed to reflect this
comment. One reviewer commented that a statement in the report was overly speculative. The
report language was edited to clearly indicate that the statement is speculative. Specific technical
definitions and information related to an accident event were contributed by one reviewer who
also provided consistency between language of the report and correct technical terminology as
IV
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used in standard National Fire Protection Association (NFPA) documentation. Extensive changes
were made to the sections Extinguishing Mechanisms of Carbon Dioxide and Life Safety
Considerations of Carbon Dioxide on the advice of one reviewer. Most other comments were
minor editorial remarks generally for clarification. All comments were addressed in the final
document.
EPA wishes to acknowledge everyone involved in this report and thanks all reviewers for their
extensive time, effort, and expert guidance. EPA believes the peer reviewers provided information
necessary to make this document technically stronger. Without the involvement of peer reviewers
and industry contacts this report would not be possible. EPA accepts responsibility for all
information presented and any errors contained in this document.
Stratospheric Protection Division (6205J)
Office of Atmospheric Programs
U.S. Environmental Protection Agency
Washington, DC 20460
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Table of Acronyms
AHJ
CATAMA
CCOHS
CEA
CFR
DOE
EPA
GPO
GVEq
HAG
HTOC
IAC
IMO
IRI
NFPA
NIOSH
NMERI
NTIS
NRC
CDS
OSHA
SCBA
SOLAS
UNEP
USCG
VdS
authorities having jurisdiction
Committee on Aviation Toxicology, Aero Medical Association
Canadian Center for Occupational Health and Safety
Comite Europeen des Assurances
Code of Federal Regulations
Department of Energy
Environmental Protection Agency
Government Printing Office
Gas Volume Equivalent
Halon Alternative Group
Halon Technical Options Committee
Information Access Company
International Maritime Organization
Industrial Risk Insurers
National Fire Protection Association
National Institute for Occupational Safety and Health
New Mexico Engineering Research Institute
National Technical Information Service
Nuclear Regulatory Commission
ozone-depleting substance
Occupational Safety and Health Administration
Self-Contained Breathing Apparatus
Safety of Life at Sea
United Nations Environment Programme
United States Coast Guard
VdS Schadenverhiitung
w
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Introduction
This paper provides information on the use and effectiveness of carbon dioxide in fire protection
systems and describes incidents involving inadvertent exposure of personnel to the gas. Because
carbon dioxide fire extinguishing systems will likely be used in place of those based on halon in
some applications, this paper attempts to provide an increased awareness of the potential dangers
associated with the use of carbon dioxide. EPA recognizes the environmental benefits of using
carbon dioxide, but is concerned that personnel accustomed to the use of halon fire suppression
systems may not be properly alerted to the special hazards of carbon dioxide. Governmental,
military, civilian, and industrial sources were researched to obtain information on deaths and
injuries associated with the use of carbon dioxide as a fire extinguishing agent. An examination of
the risks associated with carbon dioxide extinguishing systems is also presented.
Carbon Dioxide as an Extinguishing Agent
Fire protection applications generally can be divided into two basic categories: 1) applications that
allow the use of water-based sprinklers and 2) special hazards that require the use of some other
fire extinguishing agent such as carbon dioxide, halon, halon replacements, dry chemicals, wet
chemicals, or foams. According to industry consensus, special hazard applications comprise
approximately 20 percent of total fire protection applications. Of the special hazard applications,
approximately 20 percent of the market (based on dollars) is protected by carbon dioxide
extinguishing agents. Carbon dioxide has been used extensively for many years in the special
hazard fire protection industry worldwide. Between the 1920s and 1960s, carbon dioxide was the
only gaseous fire suppression agent used to any degree, but halon-based systems were used
extensively beginning in the 1960s. Carbon dioxide continues to be used in numerous applications
around the world for the extinguishment of flammable liquid fires, gas fires, electrically energized
fires and, to a lesser degree, fires involving ordinary cellulosic materials such as paper and cloth.
Carbon dioxide can effectively suppress fires of most materials with the exception of active
metals, metal hydrides, and materials containing their own oxygen source, such as cellulose nitrate
(Wysocki 1992). The use of carbon dioxide is limited primarily by the factors influencing its
method of application and its intrinsic health hazards.
Carbon dioxide is used internationally in marine applications in engine rooms, paint lockers,
vehicle transport areas on cargo vessels, and in flammable liquid storage areas (Willms 1998).
Large marine engine room systems may require as much as 20,000 Ib of carbon dioxide per
system. Carbon dioxide fire suppression systems are currently being used by the U.S. Navy and in
commercial shipping applications.
The steel and aluminum industries also rely heavily on carbon dioxide fire protection. In the
aluminum industry, for example, the rolling mill process requires the use of kerosene-like
lubricants and coolants. Fires are prevalent in this application, occurring on the average of 1 per
week in the typical aluminum plant (Wysocki 1998, Bischoff 1999). One particular aluminum
processing company averages about 600 system discharges per year worldwide in all their fire
protection applications using carbon dioxide, such as rolling mills, control rooms, and aluminum
sheet printing (Stronach 1999). Many carbon dioxide systems in the metal processing industry are
rapid discharge local application systems. In these applications, the carbon dioxide storage
Carbon Dioxide as a Fire Suppressant: 1
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containers are located close to the outlet nozzles such that liquid carbon dioxide starts to
discharge from the nozzle(s) in under 5 seconds (Wysocki 1998, Stronach 1999). These local
application carbon dioxide systems range in size from 800 to 10,000 Ib of compressed carbon
dioxide (Bischoff 1999, Stronach 1999).
Carbon dioxide systems also are used in computer rooms (subfloor), wet chemistry benches,
particle board chippers, equipment dust collectors, printing presses, cable trays, electrical rooms,
motor control centers, switch gear locations, paint spray booths, hooded industrial fryers, high-
voltage transformers, nuclear power facilities, waste storage facilities, aircraft cargo areas, and
vehicle parking areas (Willms 1998, Wysocki 1998). Small carbon dioxide systems, such as those
protecting paint lockers or fryers, use approximately 50 Ib of carbon dioxide. Other systems use
an average of about 300 to 500 Ib of carbon dioxide (Willms 1998), but can use as much as 2,500
Ib (Ishiyama 1998).
Several properties of carbon dioxide make it an attractive fire suppressant. It is not combustible
and thus does not produce its own products of decomposition. Carbon dioxide provides its own
pressurization for discharge from a storage container, eliminating the need for
superpressurization. It leaves no residue, and hence precludes the need for agent clean up. (Clean
up of fire-released debris would, of course, still be necessary in the case of a fire event.) Carbon
dioxide is relatively nonreactive with most other materials. It provides three-dimensional
protection because it is a gas under ambient conditions. It is electrically nonconductive and can be
used in the presence of energized electrical equipment.
Extinguishing Mechanism of Carbon Dioxide
Flame extinguishment by carbon dioxide is predominantly by a thermophysical mechanism in
which reacting gases are prevented from achieving a temperature high enough to maintain the free
radical population necessary for sustaining the flame chemistry. For inert gases presently used as
fire suppression agents (argon, nitrogen, carbon dioxide, and mixtures of these), the extinguishing
concentration1 is observed to be linearly related to the heat capacity of the agent-air mixture
(Senecal 1999).
Although of minor importance in accomplishing fire suppression, carbon dioxide also dilutes the
concentration of the reacting species in the flame, thereby reducing collision frequency of the
reacting molecular species and slowing the rate of heat release (Senecal 1999).
Extinguishing Effectiveness of Carbon Dioxide
Carbon dioxide is the most commonly used "inert" gas extinguishing agent, followed by nitrogen
(Friedman 1992). On a volume basis, carbon dioxide is approximately twice as effective as
nitrogen (e.g., for ethanol fires, the minimum required volume ratios of carbon dioxide and
nitrogen to air are 0.48 and 0.86, respectively). However, because carbon dioxide is 1.57 times
heavier than nitrogen [44 and 28 molecular weight (MW), respectively] for a given volume, the
two gases have nearly equivalent effectiveness on a weight basis.
:As measured by the cup burner method (NFPA 2001).
Carbon Dioxide as a Fire Suppressant: 2
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Gas Volume Equivalent (GVEq) = vol. ratio for N2 / vol. ratio for CO2 =1.8
Weight Equivalent = GVEq x MWN 2 / MWC02 =1.1
The amount of carbon dioxide needed to reduce the oxygen level to a point at which various fuels
are prevented from burning is relatively high and is also at a level where humans will suffer
undesirable health effects. Table 1 presents the minimum required ratios of carbon dioxide to air
(v/v), the corresponding oxygen concentration that will prevent burning of various vapor fuels at
25NC, the theoretical minimum carbon dioxide concentration, and the minimum design
concentration of carbon dioxide for various fuels.
Table 1 refers only to gases or vapors; however, the data are also relevant to liquids or solids
because they burn by vaporizing or pyrolyzing. Generally, with a few exceptions such as hydrogen
or carbon disulfide, a reduction of oxygen to 10 percent by volume would make fires and
explosions impossible.
Use of Carbon Dioxide Extinguishing Systems
Carbon dioxide fire extinguishing systems are useful in protecting against fire hazards when an
inert, electrically nonconductive, three-dimensional gas is essential or desirable and where clean
up from the agent must be minimal. According to the NFPA, some of the types of hazards and
equipment that carbon dioxide systems protect are "flammable liquid materials; electrical hazards,
such as transformers, switches, circuit breakers, rotating equipment, and electronic equipment;
engines utilizing gasoline and other flammable liquid fuels; ordinary combustibles such as paper,
wood, and textiles; and hazardous solids" (NFPA 12).
Carbon Dioxide as a Fire Suppressant: 3
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Table 1. Required Ratios (v/v) and Minimum Carbon Dioxide Concentrations to Prevent
Combustion
Vapor Fuels
Carbon Bisulfide
Hydrogen
Ethylene
Ethyl Ether
Ethanol
Propane
Acetone
Hexane
Benzene
Methane
CO2/aira
(v/v)
1.59
1.54
0.68
0.51
0.48
0.41
0.41
0.40
0.40
0.33
02
Concentration
(%)
8.1
8.2
12.5
13.9
14.2
14.9
14.9
15.0
15.0
15.7
Theoretical
Minimum CO2
Concentration,,
60
62
41
38
36
30
27
29
31
25
Minimum
Design CO2
Concentration
72
75
49
46
43
36
34
35
37
34
a Friedman 1989.
b Coward and Jones 1952.
Carbon Dioxide as a Fire Suppressant: 4
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Life Safety Considerations of Carbon Dioxide
Health Effects
The health effects associated with exposure to carbon dioxide are paradoxical. At the minimum
design concentration (34 percent) for its use as a total flooding fire suppressant, carbon dioxide is
lethal. But because carbon dioxide is a physiologically active gas and is a normal component of
blood gases at low concentrations, its effects at lower concentrations (under 4 percent) may be
beneficial under certain exposure conditions.2
At concentrations greater than 17 percent, such as those encountered during carbon dioxide fire
suppressant use, loss of controlled and purposeful activity, unconsciousness, convulsions, coma,
and death occur within 1 minute of initial inhalation of carbon dioxide (OSHA 1989, CCOHS
1990, Dalgaard et al. 1972, CATAMA 1953, Lambertsen 1971). At exposures between 10 and 15
percent, carbon dioxide has been shown to cause unconsciousness, drowsiness, severe muscle
twitching, and dizziness within several minutes (Wong 1992, CATAMA 1953, Sechzer et al.
1960). Within a few minutes to an hour after exposure to concentrations between 7 and 10
percent, unconsciousness, dizziness, headache, visual and hearing dysfunction, mental depression,
shortness of breath, and sweating have been observed (Schulte 1964, CATAMA 1953, Dripps and
Comroe 1947, Wong 1992, Sechzer et al. 1960, OSHA 1989). Exposures to 4 to 7 percent
carbon dioxide can result in headache; hearing and visual disturbances; increased blood pressure;
dyspnea, or difficulty breathing; mental depression; and tremors (Schulte 1964; Consolazio et al.
1947; White et al. 1952; Wong 1992; Kety and Schmidt 1948; Gellhorn 1936; Gellhorn and
Spiesman 1934, 1935; Schulte 1964). Part I of Appendix B discusses human health effects of
high-concentration exposure to carbon dioxide in greater detail.
In human subjects exposed to low concentrations (less than 4 percent) of carbon dioxide for up to
30 minutes, dilation of cerebral blood vessels, increased pulmonary ventilation, and increased
oxygen delivery to the tissues were observed (Gibbs et al. 1943, Patterson et al. 1955). These
data suggest that carbon dioxide exposure can aid in counteracting effects (i.e., impaired brain
function) of exposure to an oxygen-deficient atmosphere (Gibbs et al. 1943). These results were
used by the United Kingdom regulatory community to differentiate between inert gas systems for
fire suppression that contain carbon dioxide and those that do not (HAG 1995). During similar
low-concentration exposure scenarios in humans, however, other researchers have recorded slight
increases in blood pressure, hearing loss, sweating, headache, and dyspnea (Gellhorn and
Speisman 1934, 1935; Schneider and Truesdale 1922; Schulte 1964). Part II of Appendix B
discusses these results in greater detail.
2 Appendix B discusses the lethal effects of carbon dioxide at high exposure levels (Part I) and the
potentially beneficial effects of carbon dioxide at low exposure concentrations, as well as the use of added
carbon dioxide in specialized flooding systems using inert gases (Part II).
Carbon Dioxide as a Fire Suppressant: 5
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Safety Measures
As with other fire protection systems, a number of regulatory agencies or authorities having
jurisdiction (AHJ) administer the design, installation, testing, maintenance, and use of carbon
dioxide systems. The authority that regulates the system depends on where the system is located,
the intended scenario, and the type of system. Many AHJs that regulate industrial, commercial,
and nonmarine applications utilize the NFPA consensus standard covering carbon dioxide
extinguishing systems (NFPA 12). Although the standard itself does not hold the force of law,
governments and local authorities adopt the standard as their governing fire code. Marine
applications are regulated depending on whether the vessels navigate domestic or international
waters. U.S. Coast Guard (USCG) regulations pertain to ships in domestic waters and are
published in the Code of Federal Regulations (46 CFR Part 76.15). Internationally registered
vessels are covered under the International Maritime Organization's Safety of Life at Sea
(SOLAS) (EVIO 1992). In workplaces that are land-based, the Occupational Safety and Health
Administration (OSHA) regulates the exposure to carbon dioxide in order to ensure worker
safety.
Design, Specification, and Component Approval
Generally, the process of acquiring fire suppression system approval starts with the manufacturer
"listing" its components through organizations such as Underwriters Laboratory or Factory
Mutual in the United States. Part of the listing process is the development of an instruction and
maintenance manual that includes a description of the full operation of the system along with
system drawings. Specifications or plans for the carbon dioxide system are prepared under the
supervision of an experienced and qualified person knowledgeable in the design of carbon dioxide
systems and with the advice of the AHJ. The designs are then submitted to the AHJ before
installation begins.
Installation and Testing
Installation of the carbon dioxide system is usually performed by manufacturers' representatives
or distributors. Although the installers are not given a formal accreditation or certification, they
are trained by the manufacturer regarding proper installation of system components.
The completed system is inspected and tested by appropriate personnel to meet the approval
requirements of the AHJ. Often these requirements include:
(A) Performance of a full discharge test of the entire design quantity through the piping and
into the intended hazard area, for each hazard area, if the system protects more than one. A
check to verify that the design concentration is achieved and maintained for the specified hold
time applies to total flooding type systems only.
(B) Operational checks of all devices necessary for proper functioning of the system, including
detection, alarm, and actuation.
Carbon Dioxide as a Fire Suppressant: 6
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(C) Checks for proper labeling of devices and protected areas warning occupants of the
possible discharge of carbon dioxide. In addition, signage must be present to warn personnel
to vacate the area when the alarm sounds.3
(D) Complete inspections of the system and the hazard area to ensure that the system meets
the specifications and that it is appropriate for the type of fire hazard.
Use Controls
Despite the use of carbon dioxide in fire-fighting applications above its lethal concentration,
NFPA 12 does not limit its use in occupied areas. The standard calls for safeguards such as pre-
discharge alarms and time delays to ensure prompt evacuation prior to discharge, prevent entry
into areas where carbon dioxide has been discharged, and provide means for prompt rescue of any
trapped personnel.
The standard also requires that personnel be warned of the hazards involved as well as be
provided with training regarding the alarm signal and safe evacuation procedures. In addition,
NFPA 12 requires that a supervised "lock-out" be provided to prevent accidental or deliberate
discharge of a system when persons not familiar with the system and its operation are present in a
protected space (NFPA 12).4 The Appendix to NFPA 12 lists the following steps and safeguards
that may be used to prevent injury or death to personnel in areas where carbon dioxide is
discharged:5'6
(A) Provision of adequate aisle ways and routes of exit. These areas should be kept clear at all
times.
(B) Provision of the necessary additional or emergency lighting, or both, and directional signs
to ensure quick, safe evacuation.
3No foreign language requirements (e.g., Spanish) for signage are specified by U.S. AHJs. Ideally all labels
and warning signs should be printed both in English and in the predominant language of non-English-
reading workers (NIOSH 1976).
4 A definition of a "lock-out" has been included in the 2000 edition of the NFPA 12 Standard (Willms
1999).
5 The degree of compliance with the suggestions provided in NFPA 12 varies across different facilities.
6 The 2000 edition of NFPA 12 will include an additional provision for mandatory evacuation of the
protected area prior to conducting any testing, servicing, or maintenance on the carbon dioxide system
(Willms 1999).
Carbon Dioxide as a Fire Suppressant: 7
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(C) Provision of alarms within such areas that will operate immediately upon activation of the
system on detection of the fire, with the discharge of carbon dioxide and the activation of
automatic door closures delayed for sufficient time to evacuate the area before discharge
begins.7
(D) Provision of only outward swinging, self-closing doors at exits from hazardous areas, and,
where such doors are latched, provision of panic hardware.
(E) Provision of continuous alarms at entrances to such areas until atmosphere has been
restored to normal.
(F) Provision for adding an odor to the carbon dioxide so that hazardous atmospheres in such
areas may be recognized.
(G) Provision of warning and instruction signs at entrances to and inside such areas.
(H) Provision for prompt discovery and rescue of personnel that may be rendered unconscious
or physically impaired in such areas. This may be accomplished by having such areas searched
immediately after carbon dioxide discharge stops by trained personnel equipped with proper
breathing equipment. Those rendered unconscious by carbon dioxide can be restored without
permanent injury by artificial respiration, if removed quickly from the hazardous atmosphere.
Self-contained breathing equipment and personnel trained in its use, and in rescue practices
including artificial respiration, should be readily available.
(I) Provision of instructions and drills of all personnel in the vicinity of such areas, including
maintenance or construction people who may be brought into the area to ensure their correct
action when carbon dioxide protective equipment operates.
(J) Provision of means for prompt ventilation of such areas. Forced ventilation will often be
necessary. Care should be taken to really dissipate hazardous atmospheres and not merely
move them to another location. Carbon dioxide is heavier than air.
(K) Provision of such other steps and safeguards necessary to prevent injury or death as
indicated by a careful study of each particular situation.
(L) Provision for mandatory evacuation of the protected area prior to conducting any testing,
service, or maintenance on the CO2 system.
Industrial Risk Insurers (IRI), one of the insurance companies that provides property and business
interruption insurance to large Fortune 500 companies such as Ford, General Motors, and
Chrysler (IRI 1994), uses NFPA 12 as a basis for their insurance process and has prepared an
interpretative guideline to the NFPA 12 Standard (IM 13.3.1). IM 13.3.1 interprets NFPA 12 and
also specifies the use of a "system lock-out." A system lock-out is a device that either
7 In the next edition of the NFPA 12 Standard this provision will be revised to state that time delays and
predischarge alarms that operate prior to discharge should be used (Willms 1999).
Carbon Dioxide as a Fire Suppressant: 8
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mechanically or electrically prevents the system from discharging. Examples of system lock-outs
include manually operated valves that block the flow of an agent through downstream pipe work.
Similarly, IRI also suggests that for normally unoccupied areas where fast growth fires may occur,
a "supervised intermittent time delay" may be desired. Such devices function only when personnel
are in the protected area and allow the system to discharge gas only after an extended time delay,
thus allowing personnel to egress the area prior to discharge.
International maritime use of carbon dioxide extinguishing systems is extensive. Fire protection in
these applications is covered under the regulations and requirements set forth in the International
Maritime Organization's SOLAS (EVIO 1992). As with NFPA 12, SOLAS does not prevent the
use of carbon dioxide in normally occupied areas. Also similar to NFPA, SOLAS requires that
"means be provided for automatically giving audible warning of the release of fire-extinguishing
medium into a space in which personnel normally work or to which they have access." The alarm
must operate for a suitable amount of time prior to the gas being released. Similar to NFPA 12,
SOLAS requires that access doors to the areas where fire-extinguishing medium is stored shall
have doors that open outwards. These requirements are not differentiated for carbon dioxide or
halogenated hydrocarbon or inert gas agent systems. Unlike NFPA, SOLAS mandates that
"automatic release of gaseous fire-extinguishing medium shall not be permitted" except with
respect to local application systems.
USCG regulations for carbon dioxide systems in passenger vessels are documented in 46 CFR
Part 76.15. Separate subparts describe different types of vessels. Similar to SOLAS, 46 CFR Part
76.15 stipulates manual control of cylinder activation.8 46 CFR Part 76.15 also requires that
systems using more than 300 Ib of carbon dioxide must be fitted with an "approved delayed
discharge" arranged in such a way that when the alarm sounds the carbon dioxide is not released
for at least 20 seconds. This requirement also may pertain to systems of less than 300 Ib
depending on the number of protected levels and the egress pathway configurations. To minimize
the possibility of inadvertent actuations, USCG specifies that two separate manual controls be
operated for release of carbon dioxide, thereby requiring two independent actuations to occur
before carbon dioxide discharges into the protected space. In addition, all personnel must be
evacuated from the protected space prior to performing any testing or maintenance on the carbon
dioxide system (Willms 1999).9
In land-based workplace environments, OSHA regulates the use of carbon dioxide. These
regulations are provided in 29 CFR Parts 1910.160 and 1910.162, which outline the requirements
for general and gaseous fixed extinguishing systems, respectively. Despite the fact that the
concentration of carbon dioxide needed to extinguish fires is above the lethal level, OSHA does
not prevent the use of carbon dioxide in normally occupied areas. (However, OSHA does
8 It should be noted that 46 CFR Part 76.15-20 stipulates that "Systems...consisting of not more than 300
Ib of carbon dioxide, may have the cylinders located within the space protected. If the cylinder stowage is
within the space protected, the system shall be arranged in an approved manner to be automatically
operated by a heat actuator within the space in addition to the regular remote and local controls."
9 The 2000 edition of the NFPA 12 Standard includes a chapter on marine applications mandating
evacuation of a space prior to testing and other activities (Willms 1999).
Carbon Dioxide as a Fire Suppressant: 9
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explicitly limit the use of chlorobromomethane and carbon tetrachloride as extinguishing agents
where employees may be exposed (29 CFR Part 1910.160 (b) (11).) For carbon dioxide systems,
OSHA requires a predischarge alarm for alerting employees of the impending release of carbon
dioxide when the design concentration is greater than 4 percent (which is essentially true for all
carbon dioxide systems, see Table 1). This predischarge alarm must allow sufficient time delay for
personnel to safely exit the area prior to discharge. Although it is speculative, it is likely that these
regulations would confer adequate protection only in the event of planned discharge, not
accidental discharge. Accidental discharges have occurred, however, in which adherence to
regulations has provided personnel protection, whereas some planned discharges have resulted in
injury to personnel.
The purpose of the predischarge alarm required by OSHA, NFPA, and SOLAS is to allow
occupants time to evacuate an area into which carbon dioxide will be discharged. However,
ensuring egress from spaces that are either very large or that have obstacles or complicated
passageways has proven to be difficult. Evacuation is particularly difficult once discharge begins
because of reduced visibility, the loud noise of discharge, and the disorientation resulting from the
physiological effects of carbon dioxide.
In a number of the regulations, concern is given to the possibility of carbon dioxide leaking or
flowing into adjacent, low-lying spaces such as pits, tunnels, and passageways. In these cases,
carbon dioxide can inadvertently create suffocating atmospheres that are neither visible nor
detectable.
Two examples of the ideal fire scenario and how the carbon dioxide systems/safeguards are
expected to work are described below for two applications (car parks in Japan and a marine
engine room). Carbon dioxide systems are used in Japan in car parks (known in the United States
as parking garages) such as tower parking or floor machinery parking, but not in normally
occupied car parking facilities, where clean agents are generally used. The enclosed volume of the
typical garage facility ranges from 1,000 m3 to 1,500 m3 [roughly 35,000 ft3 to 53,000 ft3], where
800 kg to 1,125 kg [1,764 Ib to 2,480 Ib] of carbon dioxide are used. The system operates
through automatic discharge with a manual override option. The typical fire scenario for a carbon
dioxide system in a tower parking or floor machinery parking facility is shown in Figure 1
(Ishiyama 1998).
Marine applications, such as engine rooms, are areas where carbon dioxide systems are often
used. The typical fire scenario for a carbon dioxide system in a large marine engine room is shown
in Figure 2. Most of these systems function through manual activation (except systems containing
less than 300 Ib [136 kg] of carbon dioxide, which correspond to enclosure volumes less than
6,000 ft3 [170 m3]). A typical engine room will be on the order of 250,000 ft3 [7,079 m3] and use
10,000 Ib [4,536 kg] of carbon dioxide (Gustafson 1998). Despite the safeguards that are required
by regulation and meant to guard against injuries associated with carbon dioxide fire extinguishing
systems, accidents resulting in injuries and deaths have occurred, primarily caused by not
following established safety procedures.
Carbon Dioxide as a Fire Suppressant: 10
-------
Figure 1. Typical Fire Scenario for a Carbon Dioxide System in a Tower Parking or
Floor Machinery Parking Facility
Fire Detector Activates
Initiate Control Panel Sequence
Actuate Manual Control
Start Time Delay (20 Seconds Minimum)
Activate Pre-Discharge Alarm
CO2 Discharges after
Time Delay
Signal Sent to Fire Station
Discharge Indicator Light On
Exhaust Area after Extinguishment
Source: Ishiyama 1998.
-------
Figure 2. Typical Fire Scenario for a Carbon Dioxide System in a Large
Marine Engine Room
Engine Room Fire
Personnel Egress
Manually Pull Vessel Fire
Alarm or General Alarm
Manually Shut Down Fuel Oil
via Remote Trips
Manually Close Vents and Doors
Notify Vessel Master
Head Count of Personnel
Master or Chief Engineer Grants
Permission to Activate System
Manually Release CO2 from Pilot Cylinders
Manually Activate System by Operating Second Mechanism that Allows
CO2 Pilot Gas to Enter the Pilot Control System. (Pilot Operated Time Delay
Will Not Allow Gas to Flow to Protected Space until Pneumatic Chamber
Pressurizes inside Time Delay. This is a Key Feature of Marine CO2 Systems.)
Pilot
Control
System
Initiate Time Delay
CO2 Powered Audible Alarm
(Typically Operates for 3 Minutes)
Power Ventilation Shuts Down
Alarm on Bridge (Optional)
Time Delay Completed
Stop Valve in CO2 Delivery Piping Opens and CO2
Discharges into Protected Space
Source: Gustafson 1998.
-------
Review of Incidents (Accidents/Deaths) Involving Carbon
Dioxide as a Fire Extinguishing Agent
A comprehensive review of carbon dioxide incidents in fire protection was undertaken by
searching governmental, military, public, and private document archives. The variability in record-
keeping practices of various organizations has impacted the success of the data collection effort.
Incident Record Search
Library/Internet Searches Completed
Literature Searches
Two literature searches were conducted. The first literature search (1975-present) was conducted
to collect information on incident reports on injuries/deaths associated with carbon dioxide as a
fire protection agent. Key words used in the searches included: death(s), incident(s), injury(ies),
accident(s), carbon dioxide (or CO2), fire extinguishing agent(s), fire suppressant(s), maritime,
marine, shipping industry, military, civilian, industry(ies), company(ies), firm(s), human, men,
worker(s), employee(s), laborer(s). All relevant articles were retrieved. The following databases
were searched:
OSHA 1973-1997
MEDLINE 1966-1997
Toxline 1965-1997
Energy SciTec 1974-1997
NTIS 1964-1997
GPO Publications Reference File
IAC Trade and Industry Database 1976-1997
Life Sciences Collection 1982-1997
Ei Compendex 1970-1977
Wilson Applied Science and Technology Abstracts 1983-1997
Chemical Safety NewsBase 1981-1997
GPO Monthly Catalog 1997
A second literature search (1970-1998) was conducted using the DIALOG OneSearch database
and general key words (e.g., CO2, carbon dioxide, and fire suppression) to determine how and
where carbon dioxide systems are being used.
National Institute for Occupational Safety and Health (NIOSH) Library Search
A search of the NIOSH database at their library in Cincinnati, Ohio, was conducted.
Carbon Dioxide as a Fire Suppressant: 13
-------
Internet Search
An Internet search using the same key words used in the library search also was
conducted within the following electronic databases:
Government Printing Office
FireDoc
NFPA Online Database
Nuclear Regulatory Commission (NRC)
The NRC public document room was visited to obtain more detailed information on incidents
involving commercial nuclear power reactors.
Professional Contacts
Contacts were asked to provide information on incidents concerning human deaths and/or injuries
associated with the accidental or intentional discharge of carbon dioxide fire protection systems.10
Details of the incident (e.g., date, site name, and location of the incident) were requested, as well
as a description of the cause of the incident and the number of people injured or killed. Although
this information was requested, the amount of information available varied by incident.
Associations/Private Companies/Government Organizations/Research Laboratories
All relevant information was retrieved directly from the following sites and/or from contacts that
were identified therein:
The Society of Fire Protection Engineers
National Association of Fire Equipment Distributors
Fire Suppression Systems Association
Hughes Associates, Inc.
Kidde International
Ansul Fire Protection
Fike Corporation
Insurance companies that specialize in high-performance risk protection
National Defense Canada
U.S. Department of the Navy
U.S. Department of Energy (DOE)
USCG
NIOSH - Division of Safety Research
10 Accidental discharges include those occurring during maintenance operations on or near the carbon
dioxide system, testing exercises, or those resulting from operator error or a faulty system component.
Intentional discharges are generally those occurring in fire situations; however, they also include some
discharges during testing exercises or due to a false alarm.
Carbon Dioxide as a Fire Suppressant: 14
-------
Center for Global Environmental Technologies, New Mexico Engineering Research
Institute (NMERI)
National Fire Laboratory, Canadian Research Council
Ship Support Agency, United Kingdom Ministry of Defense
German Contacts:
Association of German Safety Engineers
Bavarian Land Institute for Labor Protection
Bavarian Land Institute for Medicine
Coordinating Office for Labor Protection
Directorate of Fire Brigade Affairs
Environmental Department (Umweltbundesamt)
Federal Labor Association
Federal Union of Fire Extinguishers and Installation
Federal Union of Professional Safety Engineers
Federal Institute for Occupational Safety and Health
Fire Shelter Industries
German Society of Occupational Health and Hazard
German Fire Union
Home Office of the Federal State of Baden Wurttemberg
Hygiene Institute
Institute of Research for Fire Safety (Universitaet Karlsruhe)
Labor Protection and Technical Safely
Ministry of Internal Affairs
Office of Damage Prevention
Union of Safety (Insurance)
Australian Maritime Safety Authority
Richard Bromberg, HTOC representative from Brazil11
Matsuo Ishiyama, HTOC representative from Japan
Syncrude Canada Ltd.
Loss Prevention Council, U.K.
11A more detailed library search was performed to collect corroborating information on the incident
provided by this source.
Carbon Dioxide as a Fire Suppressant: 15
-------
Search Results
The results of this comprehensive data review are presented in Appendix A. From 1975 to the
present, a total of 51 carbon dioxide incident records were located that reported a total of 72
deaths and 145 injuries resulting from accidents involving the discharge of carbon dioxide fire
extinguishing systems.12 All the deaths that were attributed to carbon dioxide were the result of
asphyxiation. Details about the injuries were generally not provided in the incident reports,
although some OSHA inspections listed asphyxia as the nature of the injury.
Prior to 1975, a total of 11 incident records were located that reported a total of 47 deaths and 7
injuries involving carbon dioxide. Twenty of the 47 deaths occurred in England prior to 1963;
however, the cause of these deaths is unknown. Table 2 presents a categorical breakdown of the
carbon dioxide incident reports and the deaths/injuries identified.
Although a comprehensive review was performed, it should be noted that data developed through
this process may be incomplete because: 1) additional sources of data may be difficult to uncover
(e.g., international incidents), 2) records are incomplete, 3) agencies are not required to report, 4)
anecdotal information is sketchy and difficult to verify, and 5) fire-related deaths due to CO2 are
generally not well documented.
12 Information was requested on any incidents of death or injury resulting from the use of carbon dioxide
fire extinguishing systems. Data were requested on both fire- and nonfire-related incidents; however, it was
significantly more difficult to gather information on fire-related incidents. Injuries and fatalities from fire
situations are generally classified only as fire-related and are not broken down by the fire suppression agent
that was used. Therefore, carbon dioxide deaths and injuries from fire-related situations may not be
adequately represented. In addition, it should be noted that any discharge of carbon dioxide which resulted
in no injuries and/or deaths was not included in the analysis.
Carbon Dioxide as a Fire Suppressant: 16
-------
Table 2. Search Results
Use Category
Number of
Incidents
Deaths
Injuries
United States and Canada
1975-
Present
Before
1975
Military
Nonmilitarv
Military
Nonmilitarv
Total
9
20
3
5
37
10
19
11
3
43
15
73
0
O
91
International
1975-
Present
Before
1975
Military
Nonmilitary
Military
Nonmilitarya
Total
Total
1
21
0
3
25
62
4
39
0
33
76
119
5
52
0
4
61
152
a Included in the total international nonmilitary incidents, deaths, and injuries before 1975 are the 20
deaths resulting from the use of carbon dioxide as a fire suppressant in England from 1945 to the mid
1960s, for which the cause is unknown.
All of the 13 military incidents reported since around 1948 were marine-related. Only 11 of the 49
civilian (commercial, industrial, or state) incidents reported during the same time period were
marine-related. The remaining incidents occurred in data processing centers, nuclear power plants,
pilot training centers, airplanes, bus garages, emergency unit communication centers, waste
storage facilities, underground parking garages, steel rolling mills, motor vehicle assembly lines,
and other facilities.
Results presented in Appendix A show that accidental exposure to carbon dioxide during
maintenance or testing was found to be the largest cause of death or injury. In some cases,
personnel did not follow required safety procedures that may have prevented the injury or death
and perhaps even the exposure itself. In several instances, new procedures have been introduced
as a result of the incident. The causes of the injuries and/or deaths are summarized in Table 3.
In some cases, maintenance on items other than the fire extinguishing system itself was the cause
of the accidental discharge. The most recent reported case occurred at the Test Reactor Area,
Idaho National Engineering and Environment Lab (a major DOE site) where carbon dioxide was
accidentally released into an electrical switchgear building during routine preventative
maintenance on electrical breakers. In another recent incident on a Brazilian oil tanker docked in
harbor, a cleaning crew accidentally discharged the carbon dioxide system while working below
deck. Similarly, at the Murray Ohio Manufacturing Company, workers discharged the carbon
dioxide system while performing an installation near a detector that actuated the system. On the
Navy Replenishment Oiler, a maintenance worker lost his footing and stepped on the activation
valve while performing maintenance on an overhead light. In these incidents, it was not noted
Carbon Dioxide as a Fire Suppressant: 17
-------
whether preliminary precautionary measures were followed as stated in OSHA, SOLAS, or NFPA
guidance. However, in certain other instances, the required precautionary measures were not
followed. For example, in the USS Sumter incident, sailors were performing planned maintenance
on a carbon dioxide system in a paint locker when the system discharged. Later it was determined
that these personnel skipped three of the four preliminary steps on the Maintenance Requirement
Card.
In testing and training situations, discharges causing death and injuries were not always
accidental. In two reported incidents, the carbon dioxide system was intentionally discharged for
testing purposes and the gas escaped into an adjacent area (University of Iowa Hazardous Waste
Storage Facility, A.O. Smith Automotive Products Company). In a 1993 incident in Japan, CO2
was intentionally discharged into an outdoor pit as part of a training exercise. Personnel
subsequently entered the pit, unaware of the discharge. Two deaths occurred during a "puff test
of the carbon dioxide system onboard the Cape Diamond cargo vessel. Subsequent investigations
indicated that shipboard personnel were not evacuated from the engine room during the test, as
should have occurred in accordance with established safety procedures. Furthermore, the main
discharge valve was not closed completely, releasing more carbon dioxide than anticipated.
Carbon Dioxide as a Fire Suppressant: 18
-------
Table 3. Causes of Injuries and/or Death Associated with Carbon Dioxide Discharges After
1975."
Cause of Injuries/Death
Accidental Discharge During
Maintenance/Repairs to the Carbon
Dioxide System
Accidental Discharge During
Maintenance in the Vicinity of
Carbon Dioxide System
Accidental Discharge During
Testing
Accidental Discharge During Fire
Situation
Accidental Discharge from Faulty
Installation or System Component
Accidental Discharge from
Operator Error
Accidental Discharge - False Alarm
Intentional Discharge During
Testing/Training
Intentional Discharge During Fire
Situation
Intentional Discharge - False Alarm
Incident
Navy Aircraft Carrier (1993)
USS Sumter
Turbo Generator
Little Creek Naval
Navy Aircraft Carrier (1980)
Cartercliffe Hall Cargo Vessel
Carolina Fire Protection
Automated Fire Suppression
Systems
Autoridad Energia Electrica-Planta
Daguao
Brazilian Oil Tanker
Murray Manufacturing Co.
Navy Replenishment Oiler
Oiler Kalamazoo
Navy Submarine Tender
SS Lash Atlantico
Stevens Technical Services Inc.
Test Reactor Area, Idaho National
Engineering and Environment Lab
Cape Diamond
LNG Carrier
Surry Nuclear Power Station
Dresden Sempergalerie
Hope Creek
French Data Center
Car Park (Japan)
Consolidated Edison Co. Barge
Meredith/Burda Corporation
U. of Iowa Hazardous Waste
Storage Facility
Japanese Outdoor Pit
A.O. Smith Automotive Products
Company
Navy Aircraft Carrier (1966)
Australian Naval Ship Westralia
Airline Constellation
Ravenswood Aluminum
Corporation
Muscle Shoals Construction Site
Japan
Reference13
Darwin 1997
Heath 1993
Allen 1997
Heath 1993
Darwin 1997
Warner 1991
Allen 1997
OSHA 1999
OSHA 1999
Bromberg 1998
McDonald 1996
Darwin 1997
Heath 1993
Darwin 1997
Hagerl981
OSHA 1999
Caves 1998
Marine Casualty Investigation
Report 1996
Paci 1996
Wamick 1986
Drescher and Beez 1993
Caves 1998
Grosetal. 1987
Ishiyamal998
OSHA 1998
OSHA 1999
Bullard 1994
Ishiyamal998
OSHA 1999
Darwin 1997
Webb 1998
Gibbons 1997
OSHA 1999
OSHA 1999
Ishiyamal998
a Incidents where the cause of discharge was uncertain are not included in the table.
b References from Table 3 are listed in Appendix A.
Carbon Dioxide as a Fire Suppressant: 19
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Examining the Risks Associated with Carbon Dioxide
Extinguishing Systems
The risk involved with the use of carbon dioxide systems is based on the fact that the level of
carbon dioxide needed to extinguish fires (and, thus, to protect an enclosure) is many times
greater than the lethal concentration. For instance, the minimum design concentration to suppress
a propane fire is 36 percent. This concentration of carbon dioxide can produce convulsions,
unconsciousness, and death within several seconds. Since carbon dioxide cylinder store rooms are
often relatively small compared to the protected areas, inadvertent discharges into these store
rooms will also produce levels much higher than the lethal level. Because the consequences of
exposure happen quickly and without warning, there is little or no margin for error.
It is intended that total flooding carbon dioxide systems be designed such that human exposure
does not occur during fire-fighting scenarios. Predischarge alarms and time delays are prescribed
in NFPA 12, OSHA, and SOLAS guidelines to prevent such exposure. Hence, relatively few
accidents involving carbon dioxide systems occur during fire events; rather, accidents most often
occur during maintenance of the carbon dioxide system itself, during maintenance around the
carbon dioxide system, or to a more limited extent, during testing of the fire suppression system.
Of the accidental discharges that occurred during maintenance, results of the survey indicated that
the deaths and/or injuries from carbon dioxide exposure were caused by: 1) inadvertently
actuating the system because there was a lack of adequate safety procedures to prevent such
discharges, 2) failure to adhere to safety procedures, or 3) low technical proficiency of personnel
in the vicinity of the carbon dioxide system.
Although the risk associated with the use of carbon dioxide for fire protection in protected
enclosures is fairly well understood by regulators, standard-setting bodies, and insurers, the risk of
carbon dioxide may not be well understood by the maintenance workers who perform functions
on or around carbon dioxide systems. The failure to adhere to prescribed safety measures is a
demonstration of this lack of understanding and appreciation of the dangers associated with
carbon dioxide. Precautionary measures must be mandated to ensure that personnel follow strict
guidelines, even if those personnel are simply entering the storage areas where the carbon dioxide
system cylinders and components are being housed.
This point is exemplified by the German experience with the use of carbon dioxide in fire
protection. In Germany, a large number of carbon dioxide systems are used to protect facilities
and installations. Most of these are equipped with automatic release of carbon dioxide, even in
occupied spaces. Despite the relative abundance of carbon dioxide systems in Germany and an
exhaustive search of German records for accidents involving carbon dioxide, only one reported
nonfire event was found. Personal communication with a number of sources (Brunner 1998,
Schlosser 1997, Lechtenberg-Autfarth 1998) supports the finding that relatively few accidents
during nonfire events have occurred with carbon dioxide in Germany. (It should be noted,
however, that accidents during fire events were more difficult to locate because German data
sources did not distinguish between fatalities and injuries caused by the fire and fatalities and
injuries caused by the use of carbon dioxide.) The good safety record of the German experience
may be attributed to their approach in installing and operating carbon dioxide systems.
Carbon Dioxide as a Fire Suppressant: 20
-------
In Germany (and much of Europe), unlike in the United States, only certified carbon dioxide-
specialized installers are allowed to install the carbon dioxide systems. Once the system is
installed, it is checked and approved by VdS Schadenverhiitung (VdS), an approval body
much like Factory Mutual. Regulations on system operations are strictly enforced and ensure that
time delays are adequate to allow egress, that the alarms are functioning properly, and that rules
and warnings are posted in the vicinity of the carbon dioxide system. Approval is granted to use
the system only if it meets all the standards and requirements. In addition, according to the
Comite Europeen des Assurances (CEA),13 the carbon dioxide installation and protected risk are
required to be inspected at least once a year by an expert of the AHJ (CEA 1997).
In addition to the system of double and triple checks imposed by the German authorities, the
prevalence of carbon dioxide use in Germany may have provided increased awareness and
education of the agent's risks and dangers.
Because of the widespread use of Hal on 1301 in the United States, which is safer than carbon
dioxide at fire-fighting concentrations, there may be a lower awareness of the hazards surrounding
carbon dioxide use. Experience has shown that a relatively higher margin of safety has been
experienced with the use of Hal on 1301 compared to carbon dioxide. This high safety margin may
add to the lack of awareness of the dangers involved with using carbon dioxide systems.
Conclusion and Recommendations
A review of accidental deaths or injuries related to carbon dioxide use in fire protection indicates
that the majority of reported incidents occurred during maintenance on or around the carbon
dioxide fire protection system. In many of the situations where carbon dioxide exposure led to
death or injury during maintenance operations, the discharge resulted from personnel
inadvertently touching, hitting, or depressing a component of the system. In some cases,
personnel did not adhere to the precautionary measures prescribed. In other cases, the safety
measures were followed, but other accidental discharge mechanisms occurred.
Examination of the accident records shows that a disproportionately large number of accidents
involving carbon dioxide have occurred on marine vessels. A number of factors may play a part in
these occurrences. First, a limited number of personnel on the ship's crew have training and
authority to activate the carbon dioxide system (Gustafson 1998). These few crew members are
very well trained regarding the system's operation, however, the remaining personnel would not
have the same level of sophisticated knowledge. In particular, new crew members and contracted
maintenance workers may be unfamiliar with a ship's particular installation, even if they are aware
of the potential dangers of carbon dioxide systems in general. This unfamiliarity could result in an
inadvertent actuation, and it is therefore important that ship operators provide instruction on and
require adherence to ship-specific procedures (Hansen 1999). The lack of training may cause
certain personnel to touch, tamper, or hit system components, which then trigger activation. In
addition, untrained personnel may disregard warning signs or alarms because they have not been
adequately informed of the hazards. In addition, because of the design of many shipboard systems,
the manual activation mechanism is sometimes a cable connected from a lever to the actuation
13 The CEA is the federation of national insurance company associations in European market economy
countries (CEA 1997).
Carbon Dioxide as a Fire Suppressant: 21
-------
device. In some designs the cable is not enclosed in a protective casing where it attaches to the
pilot cylinders. The exposed nature of this device makes accidental deployment easier. In most
system designs, however, the cable runs in conduit with pulleys to provide for turns and bends in
the cable run. Furthermore, two separate controls are necessary to activate USCG-approved
shipboard systems over 300 Ib, thereby reducing the risk of accidental discharge resulting from
exposed cables (Wysocki 1999).
Another factor influencing the safety record of marine applications is the nature of the regulatory
requirements governing use of carbon dioxide systems. Maritime regulations (46 CFRPart 76.15
and SOLAS) do not provide detailed requirements to ensure safety of personnel. These maritime
regulations can be contrasted with the NFPA standard that has more specific suggestions to
protect personnel against the adverse effect of carbon dioxide. Improvement of maritime
regulations would at least provide specific requirements that would presumably help reduce the
accidental exposures that occur in marine applications.
Additionally, in certain instances language barriers may present a source of additional risk. For
example, if signage and training manuals are available only in English, non-English-reading
personnel may not receive adequate or timely warning. Hence, making these materials available in
the predominant language of non-English-reading workers may help to educate personnel and
thereby reduce risks.
Carbon Dioxide as a Fire Suppressant: 22
-------
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Carbon Dioxide as a Fire Suppressant: 25
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APPENDIX A
Death and Injury Incidence Report
Carbon Dioxide as a Fire Suppressant (Appendix A): Al
-------
DEATH AND INJURY INCIDENCE REPORTS ASSOCIATED WITH CARBON DIOXIDE TOTAL FLOODING FIRE EXTINGUISHING SYSTEMS
Name/Site
Date
Location
Use Category
Number
Killed
Number
Injured
Summary of Cause
Sources
UNITED STATES AND CANADA1*
1
2
3
4
5
6
7
Test Reactor Area, Idaho
National Engineering and
Environment Lab
Consolidated Edison Co.
University of Iowa Hazardous
Waste Storage Facility
Murray Ohio Manufacturing
Company
M/V Cape Diamond/Norshipco
Navy Aircraft Carrier
Navy Ship USS Sumter/Little
Creek Naval Amphibious Base
July 28,
1998
February
15, 1996
June 16,
1994
December
31, 1993
March 3,
1993
January 16,
1993
July 30,
1992
Idaho
New York
Iowa City, IA
Lawrenceburg,
TN
Norfolk, VA
In Port, U.S.
Norfolk, VA
Government-
Owned Test
Facility
Commercial
State
Commercial
Military
Military
Military
1
1
0
0
2
0
2
13
0
2
2
6
3
1
The CO2 system in an electrical switchgear building of the
Engineering Test Reactor Building complex unexpectedly
actuated during routine preventative maintenance on an
electrical system.
A false fire trip of the system occurred on a barge used to
generate electricity. The victim was probably overcome while
working to reset a CO2 distribution valve and a plunger
controlling the switch for the ventilation system.
A fire suppression system test released too much CO2. During
the release, a door was blown open and CO2 escaped into an
adjacent area.
A total flooding CO2 system accidentally discharged during
installation of a new piece of duct work on a flammable liquid
paint spray booth (located near the CO2 detector).
The injuries and fatalities occurred during a "puff" test of the
ship's low pressure CO2 fire suppression system. Reports
indicated that personnel had not been evacuated from the
engine room during the test, and that the main discharge valve
was not closed completely, releasing more carbon dioxide than
anticipated.
A CO2 fire suppression system was accidentally tripped during
routine maintenance.
Three sailors were performing planned maintenance on a CO2
system in a paint locker when the system discharged. They
were asphyxiated and two died. The sailors skipped three of
the four preliminary steps on the Maintenance Requirement
Card.
Caves 1998
The Idaho
Statesman
1998
OSHA 1998
Bullard 1994
McDonald
1996
Hurley 1996
Marine
Casualty
Investigation
Report 1996
Willms 1999
Darwin 1997
Heath 1993
14 North American incidents are listed in reverse chronological order.
Carbon Dioxide as a Fire Suppressant (Appendix A): A2
-------
8
9
10
11
12
13
14
15
16
Name/Site
Muscle Shoals Construction Site
Autoridad Energia Electrica-
Planta Daguao
Preserver Warship
Ravenswood Aluminum
Corporation
Lukens Steel Company
Oiler Kalamazoo
Meredith/Burda Corporation
Navy Replenishment Oiler
Surry Nuclear Power Station
Date
September
26, 1991
April 3,
1991
January 14,
1991
June 18,
1990
July 14,
1988
1987
December
3, 1987
January,
1987
December
9, 1986
Location
Muscle Shoals,
Alabama
San Juan, PR
Quebec City,
Canada
Ravenswood,
WV
Conshohocken,
PA
Kalamazoo, MI
Casa Grande, AZ
At Sea, U.S.
Richmond, VA
Use Category
Commercial
State
Government
Commercial
Commercial
Commercial
Military
Commercial
Military
Commercial
Number
Killed
1
0
1
2
1
1
0
1
4
Number
Injured
2
2
5
0
0
0
15
0
4
Summary of Cause
An employee was performing construction work in an oil
filtration building when the CO2 fire suppression system was
activated in response to a fire. The employee was trapped and
died from asphyxia. The CO2 seeped into the basement of
another building where two other employees were working.
The two employees regained consciousness.
A fixed extinguishing system was accidentally activated
during installation of CO2 cylinders. The employees were
untrained and failed to follow procedures regarding connection
of the control head on the cylinder valve.
The fatality was due to an accidental discharge of the CO2 fire
extinguishing system.
The CO2 system was triggered by a small fire on the cold
rolling mill. Two security guards attempted to enter the
basement underneath the mill to reset the system 6 hours later.
There was a known concentration of CO2 in the basement but
the self-contained breathing apparatus (SCBA) units were left
in the guards' vehicle. The guards collapsed when they
reached the bottom of the stairwell leading to the basement,
where they died.
The fire suppression system for the rolling mill was manually
released, allowing CO2 into the oil cellar. The safety doors on
the cellar did not close and permitted CO2 into the hallway,
where the employee was found.
Sailors changing a light bulb in a paint locker hit the CO2
switch by accident.
A false alarm resulted in the release of a CO2 fixed
extinguishing system in a press room. The overhead door was
opened to ventilate the room because of a malfunction of the
manual shut-off valve. The CO2 spread into the fire brigade
room across the hall from the open door, exposing personnel to
the gas.
During maintenance on the overhead lighting system, a worker
lost his footing and accidentally stepped on the activation
valve.
An accidental discharge of both the CO2 and Halon
extinguishing systems was caused by water damage to the
extinguishing system control panels. The water came from a
pipe break in the feedwater system. Four died and four were
injured in a fire associated with the accident. However, it is
not clear if the release of the gases from fire extinguishing
systems were responsible for these injuries and deaths.
Sources
OSHA 1999
OSHA 1999
Sinclair 1997
Warner 1991
OSHA 1999
OSHA 1999
Heath 1993
OSHA 1999
Darwin 1997
Sinclair 1997
Warnick 1986
Carbon Dioxide as a Fire Suppressant (Appendix A): A3
-------
17
18
19
20
21
22
23
24
25
26
Name/Site
Stevens Technical Services Inc.
A.O. Smith Automotive Products
Company
Hope Creek Generating Station
Automated Fire Suppression
Systems
Ford Motor Company
Navy Repair Ship
Turbo Generator
Dry-Docked SS Lash Atlantico at
the Sun Ship, Inc. Yard
Little Creek Naval Amphibious
Base
Carolina Fire Protection
Navy Aircraft Carrier
Date
March 5,
1986
November
29, 1985
September
4, 1985
October 13,
1984
April 29,
1982
1981
June 9,
1981
1980
1980
June 20,
1980
Location
Bronx, NY
Milwaukee, WI
Hancocks
Bridge, NJ
Hapevilles, GA
At Sea, U.S.
U.S.
Chester, PA
Norfolk, VA
North or South
Carolina
At Sea, U.S.
Use Category
Commercial
Commercial
Commercial
Nuclear
Power Reactor
Commercial
Military
Commercial
Commercial
Military
Commercial
Military
Number
Killed
1
1
0
1
0
0
3
2
1
1
Number
Injured
0
0
23
1
1
1
2
0
0
2
Summary of Cause
The CO2 cylinders for a fire suppression system accidentally
discharged into the chamber in which they were stored. Upon
entering the chamber, the employee was asphyxiated.
During a test discharge of the CO2 fire suppression system, the
gas entered a larger space than anticipated by personnel,
resulting in the death of one employee. Only one of the three
employees conducting the test discharge was wearing a
respirator.
Carbon dioxide (10 tons) was inadvertently discharged into a
diesel generator fuel storage area. The warning bell and
beacon light did not operate and workers who were cleaning
the corridor walls outside of the fuel storage room with
air/water guns under pressure were not alerted. The cause of
the discharge was determined to be moisture (that entered the
CO2 control panel through openings at the top of an
inadequately installed protective panel) that shorted the CO2
control panel circuitry. The moisture was believed to have
originated from the workers cleaning the corridor walls.
During work on the CO2 suppression system protecting the pit
under the gas fill at the end of the chassis line, 18 50-lb bottles
and 6 75-lb bottles of the gas were accidentally discharged.
One employee was trapped in the pit and a second employee
passed out in an attempt to rescue him.
A CO2 fire suppression system was accidentally tripped during
routine maintenance.
An employee was checking an extended-discharge system
protecting a turbo-generator (under the acoustical hood) when
the system accidentally discharged. A transformer vault was
total-flood protected by the same system, employing a total of
1,800 Ib of C02.
The CO2 fire suppression system was tripped accidentally
during welding work in the engine room. The system
discharged CO2 and automatically shut the compartment
doors, trapping the workers in the engine room.
Similar to the USS Sumter incident described above (reference
#7), the victims ignored preliminary steps on the Maintenance
Requirement Card.
An employee of Carolina Fire Protection was checking a CO2
system in a bus garage when the system accidentally
discharged.
During routine maintenance on the system, heavy seas caused
a worker to fall and accidentally grab the conduit through
which the CO2 system activation cord ran.
Sources
OSHA 1999
OSHA 1999
U.S. NRC
1985
Caves 1998
OSHA 1999
OSHA 1999
Darwin 1997
Allen 1997
Hager 1981
Heath 1993
Allen 1997
Darwin 1997
Carbon Dioxide as a Fire Suppressant (Appendix A): A4
-------
27
28
29
30
31
32
33
34
35
36
37
Name/Site
Bulk Cargo Vessel Cartercliffe
Hall
Navy Submarine Tender
Airline Constellation
Navy Yard Oil Barge
Ship (Name Unknown)
Navy Fleet Oiler
Navy Aircraft Carrier
Pan American Pilot Training
Center
Columbia Geneva Steel Rolling
Mill (now USS Posco Industries)
DC-6 Airplane
Biscayne Fire
Date
May, 1980
March 26,
1979
1977
March 22,
1972
1970s
March 21,
1969
November
4, 1966
Late 1960s
Before
1954
1948
N/A
Location
Quebec City,
Canada
In port under
construction at a
private shipyard,
U.S.
U.S.
In Port, U.S.
Anchorage, AK
At Sea, U.S.
At Sea, U.S.
Miami, FL
Pittsburg, CA
U.S.
Miami, FL
Use Category
Commercial
Military
Commercial
Military
Commercial
Military
Military
Commercial
Industrial
Commercial
Commercial
Number
Killed
1
1
0
2
0
1
8
0
2
43 "
1
Number
Injured
0
2
1 or more
0
1
0
0
2
0
0
0
Summary of Cause
Accidental discharge during repairs resulted in a fatality.
The ship was not in commission and was undergoing
construction. Civilian shipyard workers were painting the
space behind the cage containing the CO2 cylinders when one
worker accidentally pulled the release cable.
Crew members responded to a fire alarm in the plane's cargo
compartment by releasing CO2. The CO2 also entered the
cockpit and partially incapacitated one or more of the crew.
Maintenance workers were replacing the CO2 cylinders and
accidentally discharged old cylinders during removal.
The automatic features of the CO2 system had been disabled
on the ship during repairs. A painter aboard the ship
accidentally hit the trip lever and the system discharged.
A CO2 fire suppression system was accidentally tripped during
routine maintenance.
The CO2 system tripped in response to a fire. The victims were
in a compartment separate from the fire, and did not realize
that the CO2 would be released into their location.
A CO2 system was being tested in a shop at the Pilot Training
Center. Two pilots were working on a radio in the shop,
unbeknownst to the testers. When the discharge sequence
started, they ignored the flashing red lights, hom, and
illuminated sign.
Two workers were killed by a CO2 fire extinguishing system.
A DC-6 crashed killing all the passengers. The last
transmission indicated that the CO2 fire extinguishers had been
released in the forward cargo pit moments before the crash. It
is not clear if any of the deaths can be directly attributed to
CO2 exposure.
An employee of Biscayne Fire died while servicing a CO2
system in the engine compartment of a large cruiser boat.
Sources
Sinclair 1997
Warner 1991
Darwin 1997
Gibbons 1977
CAB 1948
Darwin 1997
Vining 1997
Darwin 1997
Darwin 1997
Vining 1997
Vining 1997
CAB 1948
Gibbons 1977
Allen 1997
15 These deaths are attributed to the plane crash and are not included in the calculations of the total number of
deaths from CO2 exposure.
Carbon Dioxide as a Fire Suppressant (Appendix A): A5
-------
1975 - PRESENT
INCIDENT
TOTALS
BEFORE 1975
INCIDENT
TOTALS
TOTAL DOMESTIC
Name/Site
Date
29
Incidents
8
Incidents16
37
Incidents
Location
Use Category
' ' ' .
9 Military
20
Nonmilitary
3 Military
5 Nonmilitary
12 Military
25
Nonmilitary
Number
Killed
29 Deaths
14 Deaths
43 Deaths
Number
Injured
00
oo
Injuries
3 Injuries
91
Injuries
Summary of Cause
Sources
16 This number includes two incidents for which the date is not specified (references #35 and #37).
Carbon Dioxide as a Fire Suppressant (Appendix A): A6
-------
Location I Use Category
Summary of Cause
INTERNATIONAL1'
38
39
40
41
42
43
44
45
46
47
48
49
50
Australian Naval Ship Westralia
Oil Tanker
Unknown
French Data Processing Center
Dresden Sempergalerie
LNG Carrier SNAM Porto venere
Car Park Building
Power Station
Car park Building
Building
Outdoor pit
Underground Power Station
Building
April, 1998
1994/95?
Before
1963
December
25, 1986
January 14,
1993
October 2,
1996
October 19,
1996
May 18,
1996
December
1, 1995
October 18,
1995
November
5, 1993
October 12,
1993
February 5,
1991
Indian Ocean off
the coast of
Fremantle,
Australia
Angra dos Reis,
Brazil
England
France
Dresden,
Germany
Genoa, Italy
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Military
Commercial
Unknown
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
4
11
20
1
2
6
0
0
2
0
1
1
0
5
0
Unknown
0
10
3
4
4
1
3
0
0
2
Four sailors were repairing a fuel leak in the engine room
when the fuel ignited and started a fire. The room was sealed
and flooded with CO2.
A cleaning team working below deck accidentally tripped the
CO2 system.
A total of 20 deaths occurred in England prior to 1963 due to
theuseofCO2.
A fatal accident occurred in a data processing center in its
developmental stages. The operator activated the CO2
extinguishing manual trigger switch instead of an automatic-
manual rocker switch.
A faulty installation allowed a climate technician at the gallery
to choose the CO2 release button. In 1 1 minutes 3700 kg of
gas was released in public areas and 12 people began to suffer
from asphyxiation, 2 later died. The installers of the fire
suppressant system were held accountable.
A technician aboard the carrier accidentally activated the CO2
extinguisher during a fire. The discharge saturated 85% of the
engine room within 2 minutes. Six men who were fighting the
fire with hand extinguishers were killed.
An inadvertent discharge occurred during maintenance
activities.
An inadvertent discharge occurred during repair work.
A child locked in the space pushed the discharge button.
Guards entered the space in response.
An inadvertent discharge occurred during maintenance
activities.
CO2 was discharged during a training session in an outdoor
pit. Personnel entered the pit unaware of the discharge.
A repair worker accidentally cut a system wire causing a
discharge of CO2. Personnel entered the space after the
discharge.
An inadvertent discharge occurred during maintenance
activities.
Webb 1998
Bromberg
1998
Young 1998
Gros et al.
1987
^^^=^^^
Drescher and
Beez 1993
Paech 1995
Paci 1996
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
17 International incidents are listed in alphabetical order by country.
Carbon Dioxide as a Fire Suppressant (Appendix A): A7
-------
51
52
53
54
55
56
57
58
59
60
61
62
1975 - PRESENT
INCIDENT
TOTALS
BEFORE 1975
INCIDENT
TOTALS
TOTAL
INTERNATIONAL
Name/Site
Building
Building
Underground Car Park
Building
Cargo Ship
Underground Car Park
Building
Building
Building
Building
Car Park Building
Norwegian shipyard
Date
November
9, 1987
August 9,
1987
June 9,
1987
September
5, 1986
June 24,
1986
September
5, 1985
January 8,
1982
January 25,
1978
June 16,
1977
November
19, 1975
October 29,
1971
1970
22
Incidents
3 Incidents
25
Incidents
Location
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Japan
Norway
Use Category
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
Commercial
1 Military
21
Nonmilitary
0 Military
2 Non-
military
1 Unknown
1 Military
23
Nonmilitary
1 Unknown
Number
Killed
0
3
2
1
8
0
0
0
1
0
1
12
43 Deaths
33 Deaths
76 Deaths
Number
Injured
4
0
3
0
5
3
3
3
1
3
1
3
57
Injuries
4 Injuries
61
Injuries
Summary of Cause
A false alarm resulted in a manual discharge of the system.
An inadvertent discharge occurred during maintenance
activities.
An inadvertent discharge occurred during maintenance
activities.
An inadvertent discharge occurred during maintenance
activities.
An inadvertent discharge occurred during maintenance
activities.
An inadvertent discharge occurred during maintenance
activities.
Personnel entered the building following discharge.
An inadvertent discharge occurred during maintenance
activities.
An inadvertent discharge occurred during repair work.
An inadvertent discharge occurred during maintenance
activities.
Caused by operator.
Twelve crew members died in the ship's engine room (while
conducting routine assembly and repair work) when they were
exposed to an undetected CO2 leak from a fire-extinguishing
system.
Sources
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Ishiyama
1998
Jorde 1973
Carbon Dioxide as a Fire Suppressant (Appendix A): A8
-------
INCIDENT FINAL
TOTALS
Name/Site
Date
62
Incidents
Location
37 Domestic
25 International
Use Category
13 Military
48
Nonmilitary
1 Unknown
Number
Killed
119
Deaths
Number
Injured
152
Injuries
Summary of Cause
< . . : / . ' '..'''
Sources
Carbon Dioxide as a Fire Suppressant (Appendix A): A9
-------
References
Allen, Fred. 1997. Personal communication.
Bromberg, Richard. 1998. Gespi Aeronautics and Hal on Services, HTOC representative from
Brazil, personal communication.
Bullard, Charles. 1994. 1 hurt in test of U of I's fire system. Des Moines Register. June 18.
CAB. 1948. Civil Aeronautics Board, Accident Investigation Report. United Air Lines, Inc.,
nearMt. Carmel, Pa. CAB File No. 1-0075-48. June 17.
Caves, C. 1998. U.S. Department of Energy. Personal communication.
Darwin, B. 1997. U.S. Department of Navy, NAVSEA, personal communication.
Drescher, Jiirgen; Beez, Matthias. 1993. EINSATZ: GasausstroemungSempergalerie. UB,
December, pp. 10-11.
Gibbons, H.L. 1977. CO2 Hazards in General Aviation. Aviation, Space, and Environmental
Medicine. 48 (3): 261-263.
Gros, P., De Madre, J.; Dobel, M. 1987. Fatal Accident in a Computer Science Center:
Prevention of Risks Caused by Accidental Discharge of Gaseous Extinguishing Agents.
CCOHS Translation Series, No. 347.
Hager, Jerry. 1981. Chester Tragedy. Evening Journal. Delaware. June 10.
Heath, C. C.F. III. 1993. Paint Locker Turns Death Trap. Fathom. January/February, pp. 2-5.
Hurley, Morgan J. 1996. Accidental Discharge of CO2 Extinguishing System Kills Two. NFPA
Journal. March/April, pp. 83-84.
Idaho Statesman, The. 1998. Operations Resume at INEEL. July 31.
Ishiyama, M. 1998. Nohmi Bosai, Ltd., HTOC representative from Japan, personal
communication.
Jorde, R. 1973. Carbon Dioxide Poisoning: An Industrial Accident. Tidsskr Nor Laegeforen.
93 (21-22):1520-1521.
Marine Casualty Investigation Report. 1996. U.S. Coast Guard.
. January 17.
McDonald, R. 1996. Quick Response By An Industrial Structural Fire Brigade Saves A Man's
Life. Fire Engineering. Volume 149. pp. 28-29. August.
Carbon Dioxide as a Fire Suppressant (Appendix A): A10
-------
OSHA. 1998. Fatality Inspections Conducted Nationwide Where Carbon Dioxide Was
Implicated. Office of Management Data Systems, Occupational Safety and Health
Administration. August.
OSHA. 1999. Accident Search Detail. Occupational Safety and Health Administration, January
and February.
Paci, G. 1996. Two Men Investigated After LNG Ship Deaths. Lloyd's. October 12.
Paech, Hans Jaochim. 1995. Tod in der Dresdner Sempergalerie. Sicherheitsingenieur. pp. 18-
23. October.
Sinclair, John. 1997. Syncrude Canada Ltd. P.O. Box 4009, MD 0060, Fort McMurray,
Alberta, Canada, personal communication.
U.S. NRC. 1985. Preliminary Notification of Event or Unusual Occurrence-PNO-I-85-64a.
U.S. Nuclear Regulatory Commission Region I. September 5.
Vining, Ed. 1997. Martinez, CA, personal communication.
Warner, P. 1991. Carbon Dioxide Flooding System Kills Shipyard Worker. The Canadian
Firefighter.
Warnick, L. 1986. Inadvertent Actuation of Fire Suppression Systems - A Surry Nuclear
Power Station. Feedwater Pipe Failure. Virginia Power: Richmond, VA.
Webb, Gervase. 1998. Skipper Sacrifices Four Crew. Evening Standard. England. April
Willms, Charles. 1999. Fire Suppression Systems Association, Baltimore, MD, personal
communication.
Young, R. 1998. Loss Prevention Council, UK, Personal communication.
Carbon Dioxide as a Fire Suppressant (Appendix A): Al 1
-------
APPENDIX B
Overview of Acute Health Effects
Carbon Dioxide as a Fire Suppressant (Appendix B): B 1
-------
APPENDIX B - Overview of Acute Health Effects
Appendix B presents an overview of the acute health effects associated with carbon dioxide. Part
I discusses the dangerous, lethal effects of carbon dioxide at high exposure concentrations. The
minimum design concentration of carbon dioxide for a total flooding system is 34 percent
(340,000 ppm). When used at this design concentration, carbon dioxide is lethal. Part II discusses
the potentially beneficial effects of carbon dioxide at low exposure concentrations and the use of
added carbon dioxide in specialized flooding systems using inert gases.
PART I: Acute Health Effects of Carbon Dioxide
Carbon dioxide acts as both a stimulant and depressant on the central nervous system (OSHA
1989, Wong 1992). Table B-l summarizes the acute health effects that are seen following
exposure to high concentrations of carbon dioxide. Exposure of humans to carbon dioxide
concentrations ranging from 17 percent to 30 percent quickly (within 1 minute) leads to loss of
controlled and purposeful activity, unconsciousness, coma, convulsions, and death (OSHA 1989,
CCOHS 1990, Dalgaard et al. 1972, CATAMA 1953, Lambertsen 1971). Exposure to
concentrations from greater than 10 percent to 15 percent carbon dioxide leads to dizziness,
drowsiness, severe muscle twitching, and unconsciousness within a minute to several minutes
(Wong 1992, CATAMA 1953, Sechzeretal. 1960).
Exposure to 7 to 10 percent carbon dioxide can produce unconsciousness or near
unconsciousness within a few minutes (Schulte 1964, CATAMA 1953, Dripps and Comroe
1947). Other symptoms associated with the inhalation of carbon dioxide in this range include
headache, increased heart rate, shortness of breath, dizziness, sweating, rapid breathing, mental
depression, shaking, and visual and hearing dysfunction that were seen following exposure periods
of 1.5 minutes to 1 hour (Wong 1992, Sechzer et al. 1960, OSHA 1989). In a study of 42 human
volunteers, following inhalation of 7.6 and 10.4 percent carbon dioxide for short periods of time
(2.5 to 10 minutes), it was reported that only about 30 percent of the subjects complained of
difficult breathing (dyspnea), although respiration was vigorously stimulated (Lambertsen 1971,
Dripps and Comroe 1947). In this study, the most common symptoms were headache and
dizziness (Lambertsen 1971, Dripps and Comroe 1947). Other symptoms described included
mental clouding or depression, muscle tremors or twitching, tingling or cold extremities, and
exhaustion (Lambertsen 1971, Dripps and Comroe 1947). Confusion to the point of
unconsciousness was reported in several subjects at both concentrations (Lambertsen 1971).
Increasing concentrations of carbon dioxide up to 7.5 percent for a period of 20 minutes had no
significant effects on accuracy of reasoning and short-term memory, although speed of
performance of reasoning tasks was significantly slowed at the higher levels (Sayers et al. 1987).
Exposure to a concentration of 6 percent carbon dioxide can produce hearing and visual
disturbances within 1 to 2 minutes (Gellhorn 1936, Gellhorn and Spiesman 1935). Acute
exposures (minutes) to 6 percent carbon dioxide affected vision by decreasing visual intensity
discrimination in 1 to 2 minutes (Gellhorn 1936) and resulted in a 3 to 8 percent decrease in
hearing.
Carbon Dioxide as a Fire Suppressant (Appendix B): B 2
-------
Table B-l. Acute Health Effects of High Concentrations of Carbon Dioxide
Carbon Dioxide Concentration
(Percent)
17-30
>10-15
7-10
6
4-5
O
2
Time
Within 1 minute
1 minute to several minutes
Few minutes
1.5 minutes to 1 hour
1-2 minutes
<16 minutes
Several hours
Within a few minutes
1 hour
Several hours
Effects
Loss of controlled and purposeful activity, unconsciousness,
convulsions, coma, death
Dizziness, drowsiness, severe muscle twitching,
unconsciousness
Unconsciousness, near unconsciousness
Headache, increased heart rate, shortness of breath, dizziness,
sweating, rapid breathing
Hearing and visual disturbances
Headache, dyspnea
Tremors
Headache, dizziness, increased blood pressure, uncomfortable
dyspnea
Mild headache, sweating, and dyspnea at rest
Headache, dyspnea upon mild exertion
Carbon Dioxide as a Fire Suppressant (Appendix B): B 3
-------
threshold in six human subjects (Gellhorn and Spiesman 1935). Headache and dyspnea were also
seen during a 16-minute exposure to 6 percent carbon dioxide in air or oxygen (White et al. 1952,
Wong 1992). Tremors were produced in human subjects exposed to 6 percent carbon dioxide for
several hours (Schulte 1964). Mental depression occurred following exposures (several hours) to
5 percent carbon dioxide (Schulte 1964, Consolazio et al. 1947). Exposure to 4 to 5 percent
carbon dioxide for 15 to 32 minutes can produce headache and dizziness, increased blood
pressure, and can produce uncomfortable dyspnea within a few minutes (Schulte 1964, Schneider
and Truesdale 1922, Patterson et al. 1955).
A concentration of 3 percent carbon dioxide produced headache, diffuse sweating, and dyspnea at
complete rest after an exposure period of several hours (Schulte 1964). Sinclair et al. (1971)
showed that 1-hour exposures of 4 human volunteers to 2.8 percent carbon dioxide resulted in
occasional mild headaches during strenuous, steady-state exercise. Menn et al. (1970) found that
in 30-minute exposures to 2.8 percent carbon dioxide, dyspnea was detected in 3 out of 8 human
volunteers during maximal exercise, but not during half-maximal or two-thirds maximal exercise.
After several hours exposure to atmospheres containing 2 percent carbon dioxide, headache and
dyspnea can occur with mild exertion (Schulte 1964). Table B-2 shows the physiological
tolerance time for various carbon dioxide concentrations in healthy males under exercising
conditions. Short-term exposures (5 to 22 minutes) to carbon dioxide-air mixtures (2 percent to
8.4 percent carbon dioxide) also caused a distinct hearing loss at >3 percent carbon dioxide
(Gellhorn and Spiesman 1934, 1935). No effect on the hearing threshold was observed at 2.5
percent (Gellhorn and Spiesman 1935).
Table B-2. Physiological Tolerance Time for Various Carbon Dioxide Concentrations
Concentration of Carbon Dioxide
in Air (percent by Volume)
0.5
1.0
1.5
2.0
3.0
4.0
5.0
6.0
7.0
Maximum Exposure Limit
(Minutes)
indefinite
indefinite
480
60
20
10
7
5
Less than 3
Source: Compressed Gas Association 1990.
Carbon Dioxide as a Fire Suppressant (Appendix B): B 4
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Carbon dioxide is normally present in the atmosphere at a concentration of 0.03 percent (NFPA
12, Wong 1992). It is also a natural end product of human and animal metabolism. As a result,
carbon dioxide dramatically influences the function of major vital processes, including control of
breathing, vascular dilation or constriction (particularly in certain brain tissues), and body fluid
pH.
The most familiar effect of inhaled carbon dioxide is its stimulant action upon respiration
(Lambertsen 1971). The respiratory system acts as a physiologic buffer system (Jensen 1980). It is
controlled by a typical feedback mechanism where the respiratory center responds directly to
alterations in blood pH (i.e., changes in blood H+ concentrations), and the alveolar ventilation rate
in turn can regulate H+ concentration. When blood H+ concentrations rise above normal levels,
alveolar ventilation is stimulated, and the concentration of carbon dioxide in the blood is reduced.
The H+ concentration falls toward normal level, eliminating the stimulus to an increased
ventilatory rate. Greatly elevated carbon dioxide concentrations can lead to respiratory acidosis if
the capacity of the blood buffering system is exceeded. In response, respiratory excretion of
carbon dioxide occurs rapidly through an increase in the ventilation rate.
Immediately after exposure to elevated carbon dioxide levels, the minute ventilation, tidal volume
(total volume of air inhaled and exhaled during quiet breathing), alveolar carbon dioxide, and
acidity of the blood are elevated (Glatte et al. 1967). Acute exposure to 1 percent and 1.5 percent
carbon dioxide is tolerated quite comfortably. Very little noticeable respiratory stimulation occurs
until the inspired carbon dioxide concentration exceeds about 2 percent (Glatte et al. 1967,
Lambertsen 1971). At 3 percent carbon dioxide, measurable increases in pulmonary ventilation,
tidal volume, and arterial PC02 occur (Glatte et al. 1967). Respiratory stimulation then increases
sharply until inspired carbon dioxide concentrations of about 10 percent are reached (Lambertsen
1971). Between 10 and 30 percent inspired carbon dioxide, the increase in respiratory minute
volume (the product of tidal volume and respiratory rate) is less per unit of rise in inspired carbon
dioxide than with the lower concentrations (Lambertsen 1971). Within 1.5 minutes of inhalation
of 30 percent carbon dioxide in oxygen, ventilation suddenly declines, and convulsions occur
(Lambertsen 1971).
Carbon dioxide also affects the circulatory system. If the concentration of carbon dioxide in the
inspired air increases, the body will compensate by increasing the respiratory depth and rate with
an accompanying increase in cardiac output (Schulte 1964). If the carbon dioxide in the breathing
atmosphere continues to increase, the increases in cardiac and respiratory rates cannot effectively
compensate (i.e., eliminate carbon dioxide) and carbon dioxide will accumulate in the blood and
other body tissues (Schulte 1964). A short-term exposure of 17 to 32 minutes in humans to 1 or 2
percent carbon dioxide has been shown to cause a slight increase in systolic and diastolic pressure
(Schneider and Truesdale 1922). A 15 to 30 minute exposure to 5 or 7 percent carbon dioxide
caused increases in blood pressure and cerebral blood flow and a decrease in cerebrovascular
resistance but no change in cardiac output (Kety and Schmidt 1948). However, in another study,
exposure to 7.5 percent carbon dioxide for 4 to 25 minutes showed an increase in cardiac output
and blood pressure (Grollman 1930). Dripps and Comroe (1947) studied the respiratory and
circulatory responses of 42 normal young men to inhalation of 7.6 and 10.4 percent carbon
dioxide for 2.5 to 10 minutes. Inhalation of both 7.6 and 10.4 percent carbon dioxide increased
the average minute volume of respiration, pulse rate, and blood pressure. Acute exposures to
Carbon Dioxide as a Fire Suppressant (Appendix B): B 5
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higher concentrations of carbon dioxide (30 to 70 percent carbon dioxide for 38 seconds) may
result in electrocardiogram changes (Wong 1992).
PART II: Effects of Added Carbon Dioxide at Low Concentrations
Carbon dioxide is useful for counteracting the effects of oxygen deficiency (Gibbs et al. 1943). In
the presence of low oxygen, carbon dioxide is beneficial because it exerts a vasodilator effect on
cerebral blood vessels (Patterson et al. 1955, Gibbs et al. 1943). Patterson et al. (1955) studied
the threshold of response of the cerebral vessels in humans following exposure to 2.5 and 3.5
percent carbon dioxide for up to 30 minutes. The results showed that the threshold for cerebral
vasodilator effects was greater than 2.5 percent, based on the absence of changes in cerebral
blood flow, vascular resistance, and arteriovenous oxygen difference seen at this exposure
concentration (Patterson et al. 1955). In the same study, inhalation of 3.5 percent carbon dioxide
produced a 10 percent mean increase in cerebral blood flow, but little change in blood pressure in
most subjects. Dilation of cerebral blood vessels may account for the severe headache also
produced by carbon dioxide inhalation (Lambertsen 1971).
Other beneficial effects of carbon dioxide in the presence of low oxygen include the fact that it
increases the ventilation of the lungs, and it shifts the hemoglobin dissociation curve so that with a
given oxygen saturation more oxygen is delivered to the tissues. A study of arterial and internal
jugular blood oxygen, carbon dioxide content, and brain function in eight healthy young men who
breathed mixtures containing low percentages of oxygen and varying ratios of carbon dioxide
indicated that normal brain function can be maintained for very short periods of time in spite of
low percentages of oxygen in the inspired air (as low as 2 percent oxygen). This study can be
summarized as follows: in four experiments, the subjects breathed 6 percent oxygen plus 5
percent carbon dioxide for 3 minutes and then 4 percent oxygen plus 5 percent carbon dioxide for
three minutes. None of the subjects lost consciousness, response to commands and memory
remained normal, and the electroencephalograms were unchanged. Two subjects were given 2
percent oxygen plus 5 percent carbon dioxide. For over 2 minutes, both were able to subtract and
obey commands, and the electroencephalograms remained unchanged. Then the deep rapid
breathing was interrupted by a single shallow respiration, the arterial oxygen saturation dropped,
and consciousness was lost (Gibbs et al. 1943).
Lambertsen and Gelfand (1995) conducted an experiment with human volunteers to study the
physiological effects of abrupt exposures to 10 percent oxygen with 4 percent carbon dioxide.
Their results showed that for 3 minute exposures at 10 percent oxygen with 4 percent carbon
dioxide and for 3 minute exposures at 10 percent oxygen without carbon dioxide, there were
several advantages that resulted from breathing carbon dioxide in the presence of low oxygen.
These included a higher end tidal oxygen partial pressure, increased ventilation, slightly lower
heart rate, stable hemoglobin saturation (above 90 percent), higher middle cerebral artery blood
velocity, and increased (above normal) brain oxygenation flow.
In instances where carbon dioxide is added in specialized flooding systems using inert gases,
different regulatory agencies treat these agents differently. For example, in the United States, EPA
does not distinguish between inert gas blends with and without added carbon dioxide. However,
Carbon Dioxide as a Fire Suppressant (Appendix B): B 6
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in the UK, inert gas blends containing added carbon dioxide are granted longer "safe exposure"
times (HAG 1995).
In conclusion, uptake of oxygen into the bloodstream in low oxygen environments can be
enhanced by the presence of carbon dioxide within a narrow concentration range.
Carbon Dioxide as a Fire Suppressant (Appendix B): B 7
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