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SECTION 1. CHEMICAL IDENTIFICATION

CHEMINFO Record Number: 789
CCOHS Chemical Name: Argon liquid

Synonyms:
Argon
Argon, refrigerated liquid
Liquid argon
Argon
Argon liquide

Chemical Name French: Argon (liquide)
Chemical Name Spanish: Argón (líquido)
CAS Registry Number: 7440-37-1
UN/NA Number(s): 1951
RTECS Number(s): CF2300000
Chemical Family: Noble gas / inert gas
Molecular Formula: Ar
Structural Formula: Ar

SECTION 2. DESCRIPTION

Appearance and Odour:
Colourless, odourless, extremely cold liquid.(7,9,10)

Odour Threshold:
Odourless

Warning Properties:
NONE - Odourless, colourless liquid. Simple asphyxiant.

Composition/Purity:
Available commercially in grades up to 99.9995% purity by volume. Commercial argon may contain small amounts of nitrogen, oxygen, carbon dioxide, carbon monoxide, hydrogen, hydrocarbons such as methane and water.(9,10,11) Liquid argon is shipped as a cryogenic liquid in vacuum-insulated cylinders, insulated portable tanks, insulated tank trucks, and tank cars.(10)

Uses and Occurrences:
Argon makes up 0.94% of air. It is used in filling incandescent and fluorescent lamps and electronic tubes; as an inert gas shield for arc welding and cutting; in creating an inert atmosphere (blanketing) when nitrogen cannot be used, for example in the production of titanium, zirconium and other reactive metals; in flushing molten metals (steel) to remove dissolved gases; in decarburization of stainless steel; and to provide a protective shield for drawing silicon and germanium crystals. Used in lasers; in Geiger- counting tubes; in plasma-jet torches (with hydrogen); in doping semiconductors with controlled amounts of impurities. Used to carry a reactant to a reaction zone, to modify the rate of a reaction by dilution and to remove reaction products.(9,10,11) Liquid argon is used for isothermal baths near the oxygen boiling point where oxygen may be too hazardous.(11)


SECTION 3. HAZARDS IDENTIFICATION

EMERGENCY OVERVIEW:
Colourless, odourless, extremely cold liquid. Will not burn. COMPRESSED GAS. Simple asphyxiant. Can displace oxygen in air. Confined space hazard. May cause frostbite.



POTENTIAL HEALTH EFFECTS

Effects of Short-Term (Acute) Exposure

Inhalation:
Argon gas is not toxic at normal temperature and pressure. However, argon is a simple asphyxiant. Simple asphyxiants can displace oxygen in the air, especially in a confined space. The lack of oxygen then causes the victim to suffocate.
Air normally contains approximately 0.94% argon and 20.9% oxygen. At 15-16% oxygen, symptoms of sleepiness, fatigue, loss of coordination, errors in judgment and confusion are masked by a state of euphoria, giving the victim a false sense of security and well-being. An oxygen concentration of 12% or lower can cause unconsciousness quickly and without warning. In some cases, disturbed respiration, abnormal fatigue, nausea and vomiting. Concentrations below 6% can result in respiratory collapse and death.(1,3,7)
Should the victim survive the effects of breathing an oxygen deficient atmosphere, some or all organs, including the central nervous system and brain, may show damage due to oxygen deprivation. These effects may or may not be reversible with time, depending on the degree and duration of the oxygen deprivation and the extent of the tissue injury.(1,2)
Small amounts of liquid argon can evaporate into very large volumes of gas. For example, one litre of liquid argon vaporizes to 842 litres of argon gas when warmed to room temperature (21 deg C at 1 atmosphere).(3)
Super-cooled vapours, such as those released from liquid argon, can cause frostbite of the upper airways following prolonged exposure. Accumulation of fluid, inflammation, and blisters can result with eventual tissue death and ulceration in the areas of greatest exposure.(4,5)

Skin Contact:
Direct contact with liquid argon or prolonged exposure to the chilled gas can produce frostbite. Symptoms of mild frostbite include numbness, prickling and itching of 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, necrosis (dead skin) and gangrene have developed in several cases. There may be no pain experienced at first, but there is intense pain when the frozen tissue thaws.(4,6)
Unprotected skin can stick to metal that is cooled by cryogenic liquids, such as liquid argon. The skin can then tear when pulled away.(4) Cryogenic liquids will quickly penetrate woven or other porous clothing materials which will then stick to the skin.(7)

Eye Contact:
Direct contact with liquid argon or prolonged contact with the chilled gas can cause frostbite of the eyes. Permanent eye damage or blindness can result. There are no reports of accidental injury from splash contact of liquid argon with the eyes.

Ingestion:
Ingestion is not an applicable route of exposure for liquid argon.

Effects of Long-Term (Chronic) Exposure

No effects of long-term exposure have been reported.

Carcinogenicity:

There is no human or animal information available.

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 or animal information available.

Reproductive Toxicity:
There is no human or animal information available.

Mutagenicity:
There is no information available.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Argon does not accumulate in the body under normal pressure.

Health Comments:
People working at low temperatures, such as workplaces where liquid argon is used, may be at risk of developing reduced body temperature (hypothermia). Symptoms may include slowing down of physical and mental responses; irritability; difficulty in speech or vision; cramps and shivers.(6,7) Susceptibility depends on the length of exposure, temperature and the individual.


SECTION 4. FIRST AID MEASURES

Inhalation:
Take proper precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment, use the "buddy" system). Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen may be beneficial if administered by trained personnel, preferably on a doctor's advice. If breathing has stopped, trained personnel should begin artificial respiration (AR) or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately. Immediately transport victim to an emergency care facility.

Skin Contact:
If frostbite develops, 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 jewelry that may restrict circulation. Carefully cut around clothing or jewelry that sticks to the skin and remove the rest of the garment. Loosely cover the affected area with a sterile dressing. DO NOT allow the victim to drink alcohol or smoke. Quickly transport victim to an emergency care facility.

Eye Contact:
If frostbite develops, quickly remove the victim from the 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:
Ingestion is not an applicable route of exposure for gases.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
Some recommendations in the above sections, such as administration of oxygen, may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation of authority obtained, as required. All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.



SECTION 5. FIRE FIGHTING MEASURES

Flash Point:
Non-flammable liquid or gas

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. Not sensitive.

Sensitivity to Static Charge:
Information not available for liquid argon.

Combustion and Thermal Decomposition Products:
None known

Fire Hazard Summary:
Argon does not burn. The volume of a given quantity of liquid argon at 101.33 kPa and -246 deg C increases 842 times when warmed to room temperature (21 deg C and 101.33 kPa).(3) Closed argon-containing containers may rupture or explode due to overpressurization when allowed to warm or in the heat of fire. Argon can displace air to the point where there is not enough oxygen to breathe. Cryogenic liquids can be particularly dangerous during fires because of their potential to rapidly freeze water. Careless use of water can lead to heavy icing, possibly blocking pressure relief valves.(4) Furthermore, the relatively warm water greatly increases the evaporation rate of the argon. If large concentrations of argon gas are present, the water vapour in the surrounding air will condense, creating a dense fog that may make it difficult to find fire exits or equipment.(12)

Extinguishing Media:
Use extinguishing media appropriate for surrounding fire.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location.
If a fire occurs in an area where argon cylinders or containers are used or stored, move cylinder or container from fire area if it can be done without risk. Carefully use water in large quantities, preferably in spray form, to cool fire-exposed containers and equipment. Reverse flow into cylinder may cause rupture. Take care not to block pressure relief valves. Stay away from ends of tanks, but be aware that flying material from ruptured tanks may travel in any direction. Withdraw immediately in case of rising sounds from venting safety device or any discolouration of tanks due to fire. If possible, avoid spraying cold areas of equipment. If it is desirable to evaporate a liquefied argon spill quickly, water spray may be used to increase the rate of evaporation if the increased vapour evolution can be controlled. DO NOT discharge a solid stream of water into liquid argon.
If liquid argon is discharging into the air, judgment should be used in deciding whether to allow the gas to escape, with the possible risk of asphyxiation, or to attempt to cut off the gas flow, depending on which is safer.(4) Where asphyxiation is not a factor, it is preferable to let the gas escape.
Firefighters may enter the area if positive pressure self- contained apparatus (MSHA/NIOSH approved or equivalent) and full Bunker Gear is worn.



NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) HAZARD IDENTIFICATION

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


SECTION 9. PHYSICAL AND CHEMICAL PROPERTIES

Molecular Weight: 39.948

Conversion Factor:
1 ppm = 1.63 mg/m3; 1 mg/m3 = 0.61 ppm at 25 deg C (calculated)

Physical State: Gas
Melting Point: -189.2 deg C (-308.6 deg F) (10)
Boiling Point: -185.9 deg C (-302.6 deg F) (9,10,11)
Relative Density (Specific Gravity): Not applicable (gas)
Solubility in Water: Slightly soluble; 3.36 vol% at 20 deg C (11,13); 2.95 vol% at 37 deg C (14)
Solubility in Other Liquids: Soluble in organic liquids.(13) Soluble in olive oil (15.9 vol% at 37 deg C).(14)
Coefficient of Oil/Water Distribution (Partition Coefficient): Gas: Log P(oct) = 0.94 (15)
pH Value: Not applicable
Viscosity-Dynamic: 0.275 mPa.s (0.275 centipoise) at - 185.9 deg C (11)
Vapour Density: 1.38 at 21.1 deg C (70 deg F) and 101.3 kPa (air = 1) (10)
Vapour Pressure: 101.3 kPa at -185.9 deg C (9)
Vapour Pressure at 50 deg C: Greater than 7000 kPa (69 atm) (estimated from graph) (9b)
Saturation Vapour Concentration: Not applicable at normal temperatures; gas
Evaporation Rate: Rapid unless the liquid argon is contained in a well- insulated vessel.
Critical Temperature: -122.3 deg C (-188.1 deg F) (10,11)
Critical Pressure: 4898 kPa (710.2 psi or 48.3 atmospheres) (11,13)

Other Physical Properties:
TRIPLE POINT: -189.4 deg C (-308.9 deg F or 83.8 deg K) at 68.9 kPa (11,16)


SECTION 10. STABILITY AND REACTIVITY

Stability:
Normally stable.

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.


Argon is inert and unreactive.

Hazardous Decomposition Products:
None known

Conditions to Avoid:
None

Corrosivity to Metals:
Not corrosive. Type 18-8 stainless steel and other austenitic nickel-chromium alloys, copper, Monel, brass, and aluminum may be used with liquid argon.(7,10)

Stability and Reactivity Comments:
When in contact with refrigerated or liquid argon, many materials (e.g. ordinary carbon steel and most alloy steels) become brittle and are likely to break without warning.
When argon is cooled below its solidification point (-189 deg C), the solid material may survive exposure to high vacuum for a considerable period. Subsequent evaporation on warming can generate high pressure and result in an explosion.(17)


SECTION 11. TOXICOLOGICAL INFORMATION

There is no animal toxicity information available.


SECTION 16. OTHER INFORMATION

Selected Bibliography:
(1) Wilkenfeld, M. Simple asphyxiants. In: Environmental and occupational medicine. 2nd ed. Edited by W.N. Rom. Little, Brown and Company, 1992. p. 535-538
(2) Casarett and Doull's toxicology : the basic science of poisons. 3rd ed. Macmillan Publishing Company, 1986. p. 359-362
(3) Compressed Gas Association. Safety guidelines for compressed gases and cryogenic liquids. In: Handbook of compressed gases. 3rd ed. Chapman and Hall, 1990. p. 70-92
(4) Riklik, L. How to work safely with cryogenic liquids (P90-24E). Canadian Centre for Occupational Health and Safety, 1990
(5) Rockswold, G., et al. Inhalation of liquid nitrogen vapour. Annals of Emergency Medicine. Vol. 11, no. 10 (Oct. 1982). p. 553-555
(6) Code of practice for safe operation of small-scale storage facilities for cryogenic liquids. (BS 5429 : 1976). British Standards Institution, 1976
(7) British Cryogenics Council. Cryogenics safety manual: a guide to good practice. 3rd ed. Butterworth Heinemann, 1991. p. 1-51
(8) Grant, W.M., et al. Toxicology of the eye. 4th ed. Charles C. Thomas, 1993. p. 1049
(9a) Braker, W., et al. Argon. In: Matheson gas data book. 6th ed. Matheson Gas Products, 1980. p. v-vii, 34-40, 710-711
(9b) Yaws, C.L. Matheson gas data book. 7th ed. McGraw-Hill, 2001. p.30
(10) Compressed Gas Association. Argon. In: Handbook of compressed gases. 3rd ed. Chapman and Hall, 1990. p. 253-258
(11) Hwang, S-C., et al. Helium group: gases. In: Kirk- Othmer encyclopedia of chemical technology. 4th ed. Vol. 13. John Wiley and Sons, 1995. p. 1-38
(12) Matheson guide to safe handling of compressed gases. Matheson Gas Products, Inc., 1983
(13) The Merck index: an encyclopedia of chemicals, drugs, and biologicals. 12th ed. Merck and Co., Inc., 1996. p. 132
(14) Lever, M.J., et al. Decompression characteristics of inert gases. Underwater physiology. Proceedings of the fourth symposium on underwater physiology. Edited by C.J. Lambertsen. Academic Press, 1971. p. 123-136
(15) Leo, A., et al. Partition coefficients and their uses. Chemical Reviews. Vol. 71, no. 6 (Dec. 1971). p. 525-616
(16) Haussinger, P., et al. Noble gases. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised ed. Volume A 17. VCH Verlagsgesellschaft, 1991. p. 485-539
(17) Urben, P.G., ed. Bretherick's handbook of reactive chemical hazards. 5th ed. Vol. 1. Butterworth- Heinemann, Ltd., 1995. p. 54

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: 2000-01-04

Revision Indicators:
WHMIS disclosure list 2003-07-09
Carcinogenicity 2003-07-09
PEL-TWA transitional 2003-12-19
Bibliography 2006-01-17
Vapour pressure at 50 deg C 2006-01-17
Relative density 2006-09-28



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