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SECTION 1. CHEMICAL IDENTIFICATION

CHEMINFO Record Number: 63
CCOHS Chemical Name: Nitrogen, liquid

Synonyms:
Molecular nitrogen
Nitrogen
Liquid nitrogen
Azote, liquide
Nitrogen (non-specific name)

Chemical Name French: Azote (liquide)
Chemical Name Spanish: Nitrógeno
CAS Registry Number: 7727-37-9
UN/NA Number(s): 1977
RTECS Number(s): QW9700000
Chemical Family: Inorganic nitrogen compound / elemental nitrogen / molecular nitrogen
Molecular Formula: N2
Structural Formula: N#N (# denotes a triple bond)

SECTION 2. DESCRIPTION

Appearance and Odour:
Colourless, odourless, extremely cold liquid.

Odour Threshold:
Odourless liquid.

Warning Properties:
POOR - The bubbling of liquid nitrogen in containers and a fog in the vicinity, due to condensation of moisture in the air, are not reliable warning properties, since they are not always present.

Composition/Purity:
Liquid nitrogen is shipped as a cryogenic liquid at pressures below 1379 kPa gage in specially authorized, thermally insulated cylinders, in heavily insulated portable containers, and in bulk in thermally insulated tank trucks and tank cars.(1,6) Liquid nitrogen may contain small amounts of liquefied oxygen, argon and other inert gases, carbon monoxide, hydrocarbons such as methane and water. See CHEMINFO record 56E for information on nitrogen gas.

Uses and Occurrences:
Nitrogen is the main component of air, comprising 78 to 79% by volume. Liquid nitrogen is used primarily as an expendable refrigerant. It is also used in the food packaging industry for refrigeration, freeze-drying and quick-freezing of foods; for bright-annealing of steel and for chilling in aluminum foundries; cryopulverizing of plastics, rubber and spices; cryoforming of metals; shrink fitting of metal parts; in medicine for quick freezing of tissues and microorganisms, as a cryotherapeutic agent; and for preservation of biological samples; as a coolant in laboratories; and in low-temperature research.(1,2,3,4)


SECTION 3. HAZARDS IDENTIFICATION

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



POTENTIAL HEALTH EFFECTS

Effects of Short-Term (Acute) Exposure

Inhalation:
Nitrogen gas is non-toxic at normal temperature and pressure. However, nitrogen is a simple asphyxiant. Simple asphyxiants displace oxygen in air and can cause symptoms of oxygen deprivation (asphyxiation) when present in high enough concentrations to significantly lower the oxygen concentration. Air normally contains approximately 78% nitrogen and 21% oxygen. The oxygen content must not fall below 18% or harmful effects will result.
Effects of oxygen deficiency are: 12-16%: breathing and pulse rate increase, muscular coordination is slightly disturbed; 10-14%: emotional upset, abnormal fatigue, disturbed respiration; 6-10%: nausea and vomiting, collapse or loss of consciousness; below 6%: convulsive movements, possible respiratory collapse and death. Since exercise increases the body's need for oxygen, symptoms will occur more quickly during exertion in an oxygen-deficient environment.(11)
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.(11,12)
Small amounts of liquid can evaporate into very large volumes of gas. For example, one litre of liquid nitrogen vaporizes to 695 litres of nitrogen gas when warmed to room temperature (21 deg C at 1 atmosphere).(1,7) In large amounts it may displace oxygen in the air and give rise to a hazardous situation. This is a particularly serious hazard in enclosed or confined spaces.
Prolonged breathing of extremely cold air may damage the lungs.(7) Super-cooled vapours, such as liquid nitrogen vapour, can cause thermal injury to the upper airways. Edema (accumulation of fluids), inflammation, charring and blisters can result with eventual dead mucosal tissue and ulceration in the areas of greatest exposure.(4)

Skin Contact:
Liquid nitrogen and the associated cold vapours and gases can produce effects on the skin similar to a thermal burn. Prolonged exposure of the skin or contact with cold surfaces can cause frostbite. There is no initial pain, but there is intense pain when the frozen tissue thaws.(7,13) 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.
Unprotected skin can stick to metal that is cooled by cryogenic liquids. The skin can then tear when pulled away.(7)

Eye Contact:
Liquid nitrogen and the associated cold vapours and gases can cause frostbite of the eyes, even when the contact is very brief. Permanent eye damage or blindness can result. There are no reports of accidental injury from splash contact of liquid nitrogen with the eyes.(10)

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

Effects of Long-Term (Chronic) Exposure

No effects of long-term exposure have been reported.

Carcinogenicity:

No human or animal information is 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:
No human or animal information is available.

Reproductive Toxicity:
No human or animal information is available.

Mutagenicity:
No information is available.

Toxicologically Synergistic Materials:
No information is available.

Potential for Accumulation:
Nitrogen does not accumulate in the body.

Health Comments:
People working at low temperatures, such as workplaces where liquid nitrogen is used as a refrigerant, may be at risk of developing reduced body temperature. Symptoms may include slowing down of physical and mental responses; irritability; difficulty in speech or vision; cramps and shivers.(5,13) 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:
Avoid direct contact. Wear chemical protective clothing if necessary. 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 any 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 emergency care facility.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves if necessary. Quickly remove victim from source of contamination. Immediately and briefly, flush with lukewarm, gently flowing water until 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 liquid nitrogen in occupational situations.

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:
Non-flammable liquid or gas. Not sensitive.

Combustion and Thermal Decomposition Products:
None known

Fire Hazard Summary:
Nitrogen does not burn. However, containers may rupture or explode in the heat of a fire. Nitrogen can displace air to the point where there is not enough oxygen to breathe.(1) 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.(7) Furthermore, the relatively warm water greatly increases the evaporation rate of the nitrogen. If large concentrations of nitrogen 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.(15)

Extinguishing Media:
Use extinguishing media appropriate for surrounding fire.

Fire Fighting Instructions:
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. Take care not to block pressure relief valves. Stay away from ends of tanks. If possible, avoid spraying cold areas of equipment. If it is desirable to evaporate a liquefied nitrogen 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 nitrogen.
If liquid nitrogen is discharging into the air, judgment should be used in deciding whether to allow the gas to escape, or to cut off the gas flow, depending on which is safer.(1) Where asphyxiation is not a factor, it is preferable to let the gas escape.



NATIONAL FIRE PROTECTION ASSOCIATION (NFPA) HAZARD IDENTIFICATION

NFPA - Health: 3 - Short exposure could cause serious temporary or residual injury.
NFPA - Flammability: 0 - Will not burn under typical fire conditions.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.

SECTION 9. PHYSICAL AND CHEMICAL PROPERTIES

Molecular Weight: 28.013

Conversion Factor:
1 ppm = 1.14 mg/m3; 1 mg/m3 = 0.875 ppm at 25 deg C (calc.)

Physical State: Gas
Melting Point: -210 deg C (-346 deg F) at 1 atmosphere.(1,2,3,5)
Boiling Point: -195.8 deg C (-320.5 deg F) at 1 atmosphere.(1,3,5,6)
Relative Density (Specific Gravity): Not applicable (gas)
Solubility in Water: Poorly soluble (1.49% v/v at 25 deg C and 1 atmosphere).(6)
Solubility in Other Liquids: Soluble in liquid ammonia
Coefficient of Oil/Water Distribution (Partition Coefficient): Not applicable
pH Value: Not applicable
Vapour Density: 0.967 at 21.1 deg C and 1 atmosphere (air = 1) (1,3)
Vapour Pressure: Not applicable. Gas at room temperature.
Vapour Pressure at 50 deg C: Greater than 7000 kPa (69 atm) (estimated from graph) (6b)
Saturation Vapour Concentration: Not applicable. Gas at room temperature.
Evaporation Rate: Rapid, unless the liquid nitrogen is contained in a well-insulated vessel.
Critical Temperature: -147 deg C (-232.6 deg F) (1,3,5)
Critical Pressure: 3400 kPa (33.54 atmospheres) (1,6)

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.


FATTY MATERIALS - Use of liquid nitrogen in cryogenic grinding of fatty materials can lead to an explosion.(8,9)
MAGNESIUM - A mixture of magnesium powder and liquid nitrogen reacts very violently when lit with a fuse, forming magnesium nitride.(8)

Hazardous Decomposition Products:
None

Corrosivity to Metals:
Not corrosive

Stability and Reactivity Comments:
For information on materials incompatible with nitrogen gas, see CHEMINFO record 56E for details.
If liquid nitrogen is exposed to air, oxygen from the air may condense into the liquid nitrogen. Liquid nitrogen contaminated with oxygen may present the same hazards as liquid oxygen and could react violently with organic materials, such as oil and grease.(8,9)


SECTION 11. TOXICOLOGICAL INFORMATION

Standard animal toxicity values are not available.

Eye Irritation:

Liquid nitrogen poured onto the eyes of rabbits for one or two seconds with the lids held apart, produced no discernable injury. When the exposure was extended to five seconds, slight lesions of the corneal were observed. By the next day, all eyes were entirely normal.(10)


SECTION 16. OTHER INFORMATION

Selected Bibliography:
(1) Compressed Gas Association. Handbook of compressed gases. 2nd ed. Van Nostrand Reinhold, 1981. p. 205-227, 412-417
(2) Kirk-Othmer encyclopedia of chemical technology. 3rd ed. Vol. 15. John Wiley & Sons, 1981. p. 932-941
(3) Nitrogen. (Data sheet I-742-89). National Safety Council, 1989. 4p.
(4) Rockswold, G., et al. Inhalation of liquid nitrogen vapour. Annals of Emergency Medicine. Vol. 11, no. 10 (Oct. 1982). p. 553-555
(5) British Cryogenics Council. Cryogenics safety manual: a guide to good practice. 3rd ed. Butterworth Heinemann, 1991. p. 1-51
(6a) Braker, W., et al. Matheson gas data book. Matheson Gas Products, Inc., 1980. p. 522-530
(6b) Yaws, C.L. Matheson gas data book. 7th ed. McGraw-Hill, 2001. p. 563
(7) Riklik, L. How to work safely with cryogenic liquids (P90-24E). CCOHS, 1990
(8) Bretherick, L. Bretherick's handbook of reactive chemical hazards. 4th ed. Butterworths, 1990. p. 49-50, 1189, 1346-1347
(9) Hempseed, J.W. Safety considerations in using liquid nitrogen. Loss Prevention Bulletin. No. 097 (Feb. 1991). p. 1-3
(10) Grant, W.M. Toxicology of the eye. 3rd ed. Charles C.Thomas, 1986. p. 664-665
(11) Wilkenfeld, M. Simple asphyxiants. Environmental and Occupational Medicine. 2nd edition. Edited by Brown and Company, 1992. p. 535-538
(12) Casarett and Doull's toxicology : the basic science of poisons. 3rd ed. Macmillan Publishing Company, 1986. p. 359-362
(13) Code of practice for safe operation of small-scale storage facilities for cryogenic liquids. (BS 5429 : 1976). British Standards Institution, 1976
(14) Position paper on the safe handling of cryogenic liquids. Canadian Standards Association, 1988
(15) Matheson guide to safe handling of compressed gases. 2nd printing. Matheson Gas Products, Inc., 1983. p. 216-225
(16) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 49

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: 1994-08-22

Revision Indicators:
Respiratory guidelines 1995-09-01
Resistance of materials 1995-09-01
EU number 1995-09-01
EU class 1995-09-01
TLV-TWA 1995-10-01
TLV comments 1995-10-01
US Transport 1998-03-01
TDG 2002-05-27
US transport 2002-12-06
Bibliography 2006-01-18
Vapour pressure at 50 deg C 2006-01-18
Relative density 2006-09-28



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