The following information has been extracted from our CHEMINFO database, which also contains hazard control and regulatory information. [More about...] [Sample Record]

Access the complete CHEMINFO database by contacting CCOHS Client Services.


CHEMINFO Record Number: 746
CCOHS Chemical Name: Carbon dioxide gas

Carbonic acid anhydride
Carbonic acid gas
Carbonic anhydride
Carbon oxide
Liquefied carbon dioxide
Refrigerated carbon dioxide
Anhydride carbonique
Carbon dioxide liquide
Carbon dioxide (non-specific name)

Chemical Name French: Dioxyde de carbone (gaz)
Chemical Name Spanish: Dióxido de carbono
CAS Registry Number: 124-38-9
UN/NA Number(s): 1013, 2187
RTECS Number(s): FF6400000
EU EINECS/ELINCS Number: 204-696-9
Chemical Family: Inorganic carbon compound / carbon oxide / carbon dioxide / inorganic acid gas / compressed gas / liquefied gas
Molecular Formula: C-02
Structural Formula: O=C=O


Appearance and Odour:
Colourless, odourless gas or extremely cold liquid under pressure or refrigeration.(24,25)

Odour Threshold:

Warning Properties:
NONE - colourless and odourless.

Depending on temperature and pressure, carbon dioxide (CO2) can exist as a solid, liquid or a gas. This review is for CO2 gas which is shipped or stored in high pressure cylinders as a liquid under its own vapour pressure of 5729 kPa at 20 deg C, in insulated containers as a refrigerated liquid, or is made and used on-site.(21) Refer to CHEMINFO 747 for information on the solid. May contain nitrogen, oxygen, argon, hydrogen, carbon monoxide, hydrogen sulfide and amines as impurities, depending on source.

Uses and Occurrences:
CO2 gas is used for the carbonation of beverages; for pH control; as a chemical intermediate; in chemical processing; as a food preservative; as an inert "blanket"; and in enhanced oil and gas recovery. Liquid CO2 is used as a refrigerant; for low temperature testing of aviation, missile and electronic components; as a fire-extinguishing agent; for stimulation of oil and gas wells and for controlling temperature in chemical reactions.(21,22,23) CO2 gas is a by-product of carbonaceous fuel combustion; is found in naturally occurring gases; is a product of animal and human metabolism, and is found naturally in the atmosphere (about 0.035%).


Colourless, odourless gas or extremely cold liquid under pressure or refrigeration. Will not burn. COMPRESSED GAS. Can displace oxygen in air. May accumulate in low areas and is a confined space hazard. Very mild central nervous system depressant. Very high concentrations may cause headache, nausea, dizziness, sweating, restlessness and disorientation. Liquefied gas may cause frostbite.


Effects of Short-Term (Acute) Exposure

Carbon dioxide (CO2) is naturally present in the atmosphere at levels of approximately 0.035%.(1,2,21) Short-term exposure to CO2 at levels below 2% (20000 ppm) has not been reported to cause harmful effects. Higher concentrations can affect respiratory function and cause excitation followed by depression of the central nervous system. High concentrations of CO2 can displace oxygen in the air, resulting in lower oxygen concentrations for breathing. Therefore, effects of oxygen deficiency may be combined with effects of CO2 toxicity.
Volunteers exposed to 3.3% or 5.4% CO2 for 15 minutes experienced increased depth of breathing. At 7.5%, a feeling of an inability to breathe (dyspnea), increased pulse rate, headache, dizziness, sweating, restlessness, disorientation, and visual distortion developed.(3) Twenty-minute exposures to 6.5 or 7.5% decreased mental performance. Irritability and discomfort were reported with exposure to 6.5% for approximately 70 minutes.(4) Exposure to 6% for several minutes, or 30% for 20-30 seconds, has affected the heart, as evidenced by altered electrocardiograms.(2,5)
Workers briefly exposed to very high concentrations showed damage to the retina, sensitivity to light (photophobia), abnormal eye movements, constriction of visual fields, and enlargement of blind spots.(6) Exposure to up to 3.0% for over 15 hours, for six days, resulted in decreased night vision and colour sensitivity.(7)
Exposure to 10% for 1.5 minutes has caused eye flickering, excitation and increased muscle activity and twitching.(2) Concentrations greater than 10% have caused difficulty breathing (dyspnea), impaired hearing, nausea, vomiting, a strangling sensation, sweating, stupor within several minutes and loss of consciousness within 15 minutes.(3) Exposure to 30% has quickly resulted in unconsciousness and convulsions.(2) Several deaths have been attributed to exposure to concentrations greater than 20%.(1,2)
Effects of CO2 can become more pronounced upon physical exertion, such as heavy work.(8,9)

Skin Contact:
CO2 gas is not irritating to the skin. Contact with liquefied CO2 can cause frostbite. Symptoms of mild frostbite include numbness, prickling and itching in the affected area. Symptoms of more severe frostbite include a burning sensation and stiffness of the affected area. The skin may become waxy white or yellow. Blistering, tissue death and gangrene may also develop in severe cases.

Eye Contact:
Exposure to very high concentrations of the gas may cause a stinging sensation.(6) Inhalation of high concentrations of CO2 has been reported to produce effects on vision. See "Inhalation" above for details. Direct contact with liquefied CO2 may cause freezing of the eye. Permanent eye damage or blindness could result.

Ingestion is not a relevant route of exposure for gases or for liquefied CO2.

Effects of Long-Term (Chronic) Exposure

Several studies have monitored workers repeatedly exposed to elevated levels of CO2 gas. Exposure to 1-1.5% for 42-44 days caused a reversible acid-base imbalance in the blood and an increased volume of air inhaled/minute (minute volume).(10,11) In another study, harmful effects were not observed in 19 brewery cellar workers repeatedly exposed to average concentrations of 1.1% CO2, with levels occasionally up to 8% for a few moments.(2) Submarine occupants exposed to 3% CO2, 16 hours/day for several weeks experienced flushing of the skin, an impaired response of the circulatory system to exercise, a fall in blood pressure, decreased oxygen consumption, and impaired attentiveness.(12) Adaptation to some of the effects of long-term exposure to CO2 has been reported.(2,9)


There is no human information available. One limited animal study cannot be evaluated.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human information available. There is limited evidence in animal studies that exposure to very high levels of CO2 gas during pregnancy may cause developmental effects.(13) It is not possible to fully evaluate these studies due to lack of information on maternal toxicity.

Reproductive Toxicity:
There is no human information available. No conclusions can be drawn from the limited animal information.

There is no information available.

Toxicologically Synergistic Materials:
Animal studies indicate that a combination of CO2 and carbon monoxide causes an increase in the rate of carbon monoxide-binding to hemoglobin.(14)

Potential for Accumulation:
Small amounts of CO2 are produced during cellular metabolism and CO2 is a normal component of the body. CO2 is present in the blood as dissolved CO2, carbonic acid, and the bicarbonate ion. The majority of CO2 is excreted from the body in exhaled air.(2)


If symptoms are experienced, remove source of contamination or move to fresh air and obtain medical advice.

Skin Contact:
GAS: Not applicable. LIQUEFIED GAS: Quickly remove victim from source of contamination and briefly flush with lukewarm, gently flowing water until the chemical is removed. DO NOT attempt to rewarm the affected area on site. DO NOT rub area or apply dry heat. Gently remove clothing or jewellery that may restrict circulation. Carefully cut around clothing that sticks to the skin and remove the rest of the garment. Loosely cover the affected area with a sterile dressing. DO NOT allow victim to drink alcohol or smoke. Quickly transport victim to an emergency care facility.

Eye Contact:
GAS: No effects expected. If irritation occurs, remove source of contamination or move to fresh air. LIQUEFIED GAS: Quickly remove victim from source of contamination. Immediately and briefly flush with lukewarm, gently flowing water until the chemical is removed. DO NOT attempt to rewarm. Cover both eyes with a sterile dressing. DO NOT allow victim to drink alcohol or smoke. Quickly transport victim to an emergency care facility.

Ingestion is not an applicable route of exposure for gases or liquefied gases.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
Non-flammable gas. Will not burn.

Lower Flammable (Explosive) Limit (LFL/LEL):
Not applicable

Upper Flammable (Explosive) Limit (UFL/UEL):
Not applicable

Autoignition (Ignition) Temperature:
Not applicable

Sensitivity to Mechanical Impact:
Stable liquid or gas. Probably not sensitive.

Sensitivity to Static Charge:
At fast flow rates from cylinders, can cause a build-up of static electricity which can ignite any flammable or explosive mixture present.(24)

Combustion and Thermal Decomposition Products:
None known

Fire Hazard Summary:
Carbon dioxide (CO2) does not burn and does not support combustion. However, cylinders or containers may rupture or explode in the heat of a fire. CO2 can displace air to the point where there is not enough oxygen to breath. It is slightly heavier than air and may accumulate in low areas posing a confined space hazard.

Extinguishing Media:
Use extinguishing media appropriate to surrounding fire conditions. CO2 is used as a fire extinguishing agent.

Fire Fighting Instructions:
Will not burn or support combustion. Evacuate area and fight fire from a safe distance or protected location.
Isolate cylinder or containers not involved in the fire and move them from the fire area, if this can be done without risk. Otherwise, cool containers or cylinders by application of hose streams and protect personnel. Application of water should begin as soon as possible and should concentrate on any unwetted portions of the container or cylinder. If exposed to high heat, cylinders or containers may rupture or explode and suddenly release massive amounts of CO2. Stay away from ends of tanks. Withdraw immediately in case of rising sounds from venting safety device or any discolouration of tanks due to fire.
CO2 is only slightly hazardous to health. Firefighters may enter the area if positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) and full Bunker gear is worn.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 44.01

Conversion Factor:
1 ppm = 1.796 mg/m3; 1 mg/m3 = 0.557 ppm at 25 deg C (calculated)

Physical State: Gas
Melting Point: Sublimes at -78.5 deg C (-109.3 deg F) at 101.3 kPa (1 atm) (21,22)
Boiling Point: Sublimes (21,22)
Relative Density (Specific Gravity): Not applicable (gas)
Solubility in Water: Slightly soluble; 83.5-90 mL/100 g at 20 deg C (21,27)
Solubility in Other Liquids: Soluble in acetone, ethanol, diethyl ether, benzene, toluene, methanol, heptane and methyl acetate and most organic liquids at 20 deg C (27)
Coefficient of Oil/Water Distribution (Partition Coefficient): Not applicable
pH Value: 3.7 (saturated aqueous solution) at 101.3 kPa (carbonic acid) (21,22)
Vapour Density: 1.522 at 21.1 deg C and 101.3 kPa (air=1) (21) 1.833 kg/m3 (0.0018 g/mL) at 21.1 deg C; 1.977 kg/m3 (0.00198 g/mL at 0 deg C; at 101.3 kPa (21)
Vapour Pressure: 3485 kPa (34.4 atm) at 0 deg C; 5729 kPa (56.5 atm) at 20 deg C (saturated liquid and vapour) (26,27)
Vapour Pressure at 50 deg C: 7200 kPa (71 atm) (estimated from graph) (21b)
Saturation Vapour Concentration: Not applicable (gas)
Evaporation Rate: Not applicable, gas.
Critical Temperature: 31.1 deg C (88 deg F) (21,22)
Critical Pressure: 7383 kPa (72.9 atm) (22,23)

Other Physical Properties:
TRIPLE POINT: -56.6 deg C (-69.9 deg F) at 518 kPa (22,27)
ABSOLUTE DENSITY: 1.833 kg/m3 (0.0018 g/mL) at 21.1 deg C; 1.977 kg/m3 (0.00198 g/mL at 0 deg C; at 101.3 kPa (21)


Normally stable. In the presence of ultraviolet light or electrical discharges, CO2 decomposes to carbon monoxide and oxygen.(22,27)

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

ACROLEIN or AZIRIDINE - violently polymerizes with the production of heat.(28)
MAGNESIUM, TITANIUM, ZIRCONIUM or MAGNESIUM-ALUMINUM ALLOY DUSTS - can ignite and/or explode when suspended in CO2.(25,28)
SODIUM PEROXIDE and ALUMINUM or MAGNESIUM or TIN POWDERS - mixtures explode in CO2 gas.(28,29)
POWDERED METALS and NITROGEN (e.g. beryllium, cerium and alloys, thorium, uranium, titanium and zirconium) - ignite on heating in mixtures of CO2 and nitrogen.(28)
LITHIUM or SODIUM - molten metal burns vigorously in CO2 gas.(28)
METAL HYDRIDES (e.g. aluminum hydride) or ALUMINUM, CHROMIUM or MANGANESE DUSTS - may ignite and/or explode at elevated temperatures.(28)

Conditions to Avoid:
Temperatures higher than 52 deg C (approximately 125 deg F).(21)

Corrosivity to Metals:
Dry CO2 is a relatively inert gas and is not corrosive to the common, commercially available metals. It may be slightly corrosive to some metals, e.g. nickel ferrous alloy, in the presence of moisture.(21)


Standard animal toxicity values are not available.

Effects of Short-Term (Acute) Exposure:

Exposure to very high concentrations (1.3-15%) for short periods of time has not resulted in any harmful effects. Extremely high concentrations (approximately 40%) have resulted in death. Exposure to 1.3 to 14.7% carbon dioxide (CO2) for 30 minutes was not incapacitating and produced no deaths in rats. Rats exposed to 15% for 30 minutes did not lose consciousness, while 40% was reported to be lethal to rats exposed for 4 hours.(14) At lethal concentrations (up to 43.2%), effects have been seen in the central nervous system, lungs, liver, kidneys and the muscle tissue of the heart (myocardium) in rats.(15) Dogs exposed to 50% CO2 for approximately 90 minutes, or 80% for several minutes, died from respiratory and cardiac failure.(16)

Effects of Long-Term (Chronic) Exposure:

Changes in body weight, nutrient metabolism, adrenal cortical activity, and blood chemistry were observed in guinea pigs following inhalation of 1.5% CO2 for up to 91 days.(17) Rats exposed to 6-10% CO2 for up to 166 days developed a brownish hair discolouration and had reversible tissue changes in the central nervous system, lungs, liver, kidneys and the muscle tissue of the heart (myocardium).(15) In another study, harmful effects were not observed in monkeys exposed to 3% CO2 for 93 days.(18)

No conclusions can be made from one incompletely reported study in which mice had repeated dermal contact with solid carbon dioxide (dry ice).(2)

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
The potential developmental effects of CO2 have been evaluated in several studies.(13) All of the studies had deficiencies with respect to experimental design and reporting or involved exposures which would most certainly have produced maternal toxicity. Therefore, it is not possible to draw any conclusions regarding teratogenicity or embryotoxicity. In one study, rats were exposed to 6% CO2 for one 24 hour period on the single days of pregnancy (days 5-21). The incidence of cardiac malformations was higher in the offspring of treated animals than in the control group, particularly when exposure was on the tenth day of pregnancy. There was also an increased incidence of skeletal malformations and stillborn pups in the exposure groups.(19) In another study, rabbits, exposed to 8% CO2 on days 21-28 of pregnancy, had offspring with decreased body weight and an increased occurrence of advanced lung maturation, an effect which may not be harmful.(20) Both of these studies lacked reporting on maternal toxicity.

Reproductive Toxicity:
No conclusions can be made from two studies on the effect of CO2 on the male rodent reproductive system. In one study, sperm shape was altered and fertility decreased in male mice exposed to very high levels (approximately 35%) of CO2 and low levels of oxygen. However, the experimental design was inadequate and conclusions cannot be made.(2) In another study, male rats were exposed to 2.5%, 5.0% or 10% CO2 for 1, 2, 4 or 8 hours. Reversible dose- and time-dependent degenerative changes were observed in the testes.(2)


Selected Bibliography:
(1) Lipsett, M.J., et al. Inorganic compounds of carbon, nitrogen and oxygen. In: Patty's Industrial Hygiene and Toxicology. Edited by G.D. Clayton et al. 4th edition. Volume II. Toxicology. Part F. John Wiley and Sons, Inc., 1994. p. 4552-4557.
(2) Criteria for a recommended standard: occupational exposure to carbon dioxide. National Institute for Occupational Safety and Health, 1976.
(3) Busby, D.E. Carbon dioxide toxicity. Space Clinical Medicine. Vol. 1 (1968). p. 381-419
(4) Sayers, J.A. et al. Effects of carbon dioxide on mental performance. Journal of Applied Physiology. Vol. 63, no.1 (July, 1987). p. 25-30
(5) Macdonald, F.M. et al. Human electrocardiogram during and after inhalation of thirty per cent carbon dioxide. Journal of Applied Physiology. Vol. 6 (November, 1953). p. 304-310
(6) Grant, W.M. et al. Toxicology of the Eye. 4th edition. Charles C. Thomas, 1993. p. 317-318
(7) Weitzman, E.O. et al. Effect on vision of repeated exposure to carbon dioxide. U.S. Naval Submarine Medical Center Report, 1969. p. 1-6
(8) Carbon dioxide. In: Documentation of the threshold limit values and biological exposure indices. 6th edition. American Conference of Governmental Industrial Hygienists, 1991. p. 222-223
(9) Finkel, A.J. Hamilton and Hardy's Industrial Toxicology. 4th edition. John Wright, 1983. p. 154-156
(10) Pingree, B.J.W. Acid-base and respiratory changes after prolonged exposure to 1% carbon dioxide. Clinical Science and Molecular Medicine. Vol. 52, no. 1 (January, 1977). p. 67-74
(11) Schaefer, K.E. Acclimatization to low concentration of carbon dioxide. Industrial Medicine and Surgery. Vol. 32, no. 1 (January, 1963). p. 11-13
(12) Schaefer, K.E. Studies of carbon dioxide toxicity: (1) Chronic CO2 toxicity in submarine medicine. Navy Department, Bureau of Medicine and Surgery, Medical Research Laboratory Report no. 181. Vol. 10 (21 August, 1951). p. 156-176
(13) Scialli, A.R. et al. Reproductive effects of chemical, physical, and biologic agents: REPROTOX. The Johns Hopkins University Press, 1995. p. 367
(14) Levin B.C. et al. Toxicological interactions between carbon monoxide and carbon dioxide. Toxicology. Vol. 47 (1987). p. 135- 164
(15) Stephens, W.M The central nervous system changes resulting from increased concentrations of carbon dioxide. Journal of Neuropathology and Clinical Neurology. Vol. 1 (1951). p. 88-97
(16) Ikeda, N. et al. The course of respiration and circulation in death by carbon dioxide poisoning. Forensic Science International. Vol. 41, no. 1,2 (April/May, 1989). p. 93-99
(17) Schaefer, K.E. et al. Effects of prolonged exposure to 1.5% carbon dioxide in air for periods up to 91 days on body weight, carbohydrate metabolism, and adrenal cortical activity in guinea pigs. Navy Department, Bureau of Medicine and Surgery, Naval Submarine Medical Research Laboratory, Report No. 256, 12 October, 1954.
(18) Stein, S.N. et al. The effects of prolonged inhalation of hypernormal amounts of carbon dioxide: I. Physiological effects on 3 percent carbon dioxide for 93 days upon monkeys. Naval Medical Research Institute Report, Bethesda, Maryland. Vol. 17 (31 August, 1959). p. 527-536.
(19) Haring, O. Cardiac malformations in rats induced by exposure of the mother to carbon dioxide during pregnancy. Circulation Research. Vol. 8 (November, 1960). p. 1218-1227
(20) Nagai, A. et al. The effect of maternal CO2 breathing on lung development of fetuses in the rabbit: morphologic and morphometric studies. American Review Respiratory Disease. Vol. 135 (1987). p. 130-136
(21a) Compressed Gas Association. Handbook of compressed gases. 3rd edition. Chapman and Hall, 1990. p. 284-300
(21b) Yaws, C.L. Matheson gas data book. 7th ed. McGraw-Hill, 2001. p. 127
(22) Pierantozzi, R. Carbon dioxide. In: Kirk-Othmer encyclopedia of chemical technology. 4th edition. Volume 5. John Wiley & Sons, 1993. p. 35-53
(23) HSDB record for carbon dioxide. Date of last update: 9508
(24) Chemical safety sheets: working safely with hazardous chemicals. Kluwer Academic Publishers, 1991. p. 190
(25) NIOSH pocket guide to chemical hazards. National Institute for Occupational Safety and Health, June 1994. p. 52-53
(26) Braker, W., et al. Matheson gas data book. 6th edition. Matheson Gas Products, 1980. p. 120-129
(27) Topham, S. Carbon dioxide. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised edition. Vol. A 5. VCH Verlagsgesellschaft, 1986. p. 165-183
(28) Urben, P.G., ed. Bretherick's handbook of reactive chemical hazards. 5th edition. Volume 1. Butterworth-Heinemann, 1995. p. 220-222
(29) Fire protection guide to hazardous materials. 11th edition. National Fire Protection Association, 1994. NFPA 491
(30) National Institute for Occupational Safety and Health (NIOSH). Carbon Dioxide. In: NIOSH Manual of Analytical Methods (NMAM(R)). 4th ed. Edited by M.E. Cassinelli, et al. DHHS (NIOSH) Publication 94-113. Aug. 1994. Available at: <>

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1996-06-24

Revision Indicators:
TLV (comments) 1997-12-01
US transport 1998-03-01
Skin protection 1998-04-01
TDG 2002-05-29
US transport 2002-12-10
PEL-TWA final 2003-12-04
PEL-STEL final 2003-12-04
PEL transitional comments 2003-12-04
Passive Sampling Devices 2005-03-06
Bibliography 2006-01-18
Vapour pressure at 50 deg C 2006-01-18
Relative density 2006-09-28

©2007 Canadian  Centre  for  Occupational  Health  &  Safety  E-mail:  Fax: (905) 572-2206  Phone: (905) 572-2981  
Mail:  250  Main  Street  East,  Hamilton  Ontario  L8N  1H6