Disclaimer: These guidelines were developed under contract using generally accepted secondary sources. The protocol used by the contractor for surveying these data sources was developed by the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and the Department of Energy (DOE). The information contained in these guidelines is intended for reference purposes only. None of the agencies have conducted a comprehensive check of the information and data contained in these sources. It provides a summary of information about chemicals that workers may be exposed to in their workplaces. The secondary sources used for supplements 111 and 1V were published before 1992 and 1993, respectively, and for the remainder of the guidelines the secondary sources used were published before September 1996. This information may be superseded by new developments in the field of industrial hygiene. Therefore readers are advised to determine whether new information is available.

OCCUPATIONAL SAFETY AND HEALTH GUIDELINE FOR NITROGEN

INTRODUCTION

This guideline summarizes pertinent information about nitrogen for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.

SUBSTANCE IDENTIFICATION

* Formula

N(2)

* Structure

(For Structure, see paper copy)

* Synonyms

Nitrogen gas

* Identifiers

1. CAS No.: 7727-37-9

2. RTECS No.: QW9700000

3. DOT UN: 1066 12 (compressed gas), 1977 21 (refrigerated liquid)

4. DOT label: Nonflammable gas

* Appearance and odor

Nitrogen is a colorless, odorless, and tasteless gas. It is often shipped under refrigeration as a cryogenic liquid.

CHEMICAL AND PHYSICAL PROPERTIES

* Physical data

1. Atomic weight: 14.0

2. Boiling point (at 760 mm Hg): -195.8 degrees C (-320.4 degrees F)

3. Specific gravity: 1.25 at 0 degrees C (32 degrees F) and 1 atmosphere pressure

4. Vapor density: 0.967

5. Melting point: -210 degrees C (-346 degrees F)

6. Vapor pressure: Not applicable.

7. Solubility: Slightly soluble in water and alcohol.

8. Evaporation rate: Not applicable.

* Reactivity

1. Conditions contributing to instability: None reported.

2. Incompatibilities: Nitrogen can combine with oxygen at high temperatures to form oxides of nitrogen and may form ammonia if in contact with hydrogen at elevated temperatures. When heated to a red heat, nitrogen can also form nitrides in contact with lithium, barium, silicon, calcium, or strontium. Cyanides can form if nitrogen is heated with carbon in the presence of alkalies or barium oxide. In contact with ozone, nitrogen can oxidize explosively.

3. Hazardous decomposition products: Not applicable.

4. Special precautions: None reported.

* Flammability

Nitrogen is not combustible.

The National Fire Protection Association has assigned a flammability rating of 0 (minimal fire hazard) to nitrogen.

1. Flash point: Not applicable.

2. Autoignition temperature: Not applicable.

3. Flammable limits in air: Not applicable.

4. Extinguishant: For small fires use dry chemical or carbon dioxide. Use water spray, fog, or regular foam to fight large fires involving nitrogen.

Fires involving nitrogen should be fought upwind from the maximum distance possible. Keep unnecessary people away; isolate the hazard area and deny entry. Isolate the area for 1/2 mile in all directions if a tank, rail car, or tank truck is involved in the fire. Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Containers of nitrogen may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. If this is not possible, cool fire-exposed containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Personnel should withdraw immediately if a rising sound from a venting safety device is heard or if there is discoloration of a container due to fire. Firefighters should wear a full set of protective clothing and self-contained breathing apparatus when fighting fires involving nitrogen.

EXPOSURE LIMITS

* OSHA PEL

The Occupational Safety and Health Administration (OSHA) does not currently regulate nitrogen.

* NIOSH REL

The National Institute for Occupational Safety and Health (NIOSH) has not established a recommended exposure limit for nitrogen.

* ACGIH TLV

The American Conference of Governmental Industrial Hygienists (ACGIH) lists nitrogen as a simple asphyxiant [ACGIH 1994, p. 28].

HEALTH HAZARD INFORMATION

* Routes of Exposure

Exposure to nitrogen can occur through inhalation of the gas or contact of the skin or eyes with the cryogenic liquid [Sittig 1991, p. 1216; Genium 1986].

* Summary of toxicology

1. Effects on Animals: Nitrogen is a simple asphyxiant that is without other significant physiologic effects [ACGIH 1991]. Applied to the eyes of rabbits for 2 seconds, liquid nitrogen caused no adverse effect. When the duration of exposure was lengthened to 5 seconds, the corneal epithelium showed slight staining when tested with fluorescein, but this effect had cleared by the next day [Grant 1986].

2. Effects on Humans: Nitrogen is a simple asphyxiant that is without other significant physiologic effects [ACGIH 1991]. Inhalation of nitrogen is dangerous only when it lowers the available oxygen in air to below life-sustaining levels [ACGIH 1991; Rom 1992]. The principal hazard associated with liquid nitrogen is rapid freezing of fingers, hands, or other tissues that contact the liquid [ACGIH 1991].

* Signs and symptoms of exposure

1. Acute exposure: The signs and symptoms of overexposure to nitrogen may include nausea, drowsiness, blue coloration of the skin and lips, unconsciousness, and death [Sittig 1991].

2. Chronic exposure: No signs or symptoms of chronic exposure to nitrogen have been reported in humans.

EMERGENCY MEDICAL PROCEDURES

* Emergency medical procedures: [NIOSH to supply]

3. Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard [29 CFR 1910.1200]). All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations.

EXPOSURE SOURCES AND CONTROL METHODS

The following operations may involve nitrogen and lead to worker exposures to this substance:

* The production and transportation of nitrogen

* Use as an inert gas (barrier or purge gas) to prevent oxidation during processing, storage, and packaging in the metallurgical, chemical, and food industries

* Use in the manufacture of incandescent lamps (bulbs)

* Use in fertilizers

* Use as a liquid to freeze or refrigerate food and biological samples

* Use in pneumatic instruments, hydraulic accumulators, and in pressure transfer equipment

* Use in the manufacture of explosives

Methods that are effective in controlling worker exposures to nitrogen, depending on the feasibility of implementation, are as follows:

* Process enclosure
* Local exhaust ventilation
* General dilution ventilation
* Personal protective equipment

Workers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR 1910.120].

Good sources of information about control methods are as follows:

1. ACGIH [1992]. Industrial ventilation--a manual of recommended practice. 21st ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

2. Burton DJ [1986]. Industrial ventilation--a self study companion. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

3. Alden JL, Kane JM [1982]. Design of industrial ventilation systems. New York, NY: Industrial Press, Inc.

4. Wadden RA, Scheff PA [1987]. Engineering design for control of workplace hazards. New York, NY: McGraw-Hill.

5. Plog BA [1988]. Fundamentals of industrial hygiene. Chicago, IL: National Safety Council.

WORKPLACE MONITORING AND MEASUREMENT

No method for the determination of a worker's exposure to airborne nitrogen has been published.

PERSONAL HYGIENE PROCEDURES

If liquid nitrogen contacts the skin, workers should flush the affected areas immediately with plenty of tepid water to reduce the freezing of tissue. Do not apply direct heat or rub frozen areas.

Clothing contaminated with liquid nitrogen should be removed immediately.

STORAGE

Compressed nitrogen should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of nitrogen should be protected from physical damage and heat and should be stored separately from ozone.

SPILLS AND LEAKS

In the event of a leak or spill involving nitrogen gas or liquid nitrogen, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:

1. Stop the leak if it is possible to do so without risk.

2. Notify safety personnel of major spills or leaks.

3. Evacuate all personnel until ventilation can restore oxygen concentrations to safe levels.

4. Emergency personnel need self-contained breathing equipment.

5. Allow the spilled nitrogen to evaporate.

SPECIAL REQUIREMENTS

U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available.

* Emergency planning requirements

Nitrogen is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (Title III) in 42 USC 11022.

* Reportable quantity requirements for hazardous releases

Employers are not required by the emergency release notification provisions in 40 CFR Part 355.40 to notify the National Response Center of an accidental release of nitrogen; there is no reportable quantity for this substance.

* Community right-to-know requirements

Employers are not required by EPA in 40 CFR Part 372.30 to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of nitrogen emitted or released from their facility annually.

* Hazardous waste management requirements

EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Although nitrogen is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above.

Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance.

RESPIRATORY PROTECTION

* Conditions for respirator use

Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Air supply respirators must be worn if the ambient concentration of nitrogen is high enough to cause an oxygen-deficient atmosphere. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergencies. Workers should only use respirators that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA).

* Respiratory protection program

Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a].

PERSONAL PROTECTIVE EQUIPMENT

Workers should use appropriate personal protective clothing and equipment that must be carefully selected, used, and maintained to be effective in preventing skin contact with liquid nitrogen. The selection of the appropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to liquid nitrogen. There are no published reports on the resistance of various materials to permeation by liquid nitrogen.

To evaluate the use of various PPE materials with liquid nitrogen, users should consult the best available performance data and manufacturers' recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components.

Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve liquid nitrogen.

Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, caustic, or other toxic substance may be splashed into the eyes.

In addition to the possible need for wearing protective outer apparel (e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk.

Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness.

Protective clothing may interfere with the body's heat dissipation, especially during hot weather or during work in hot or poorly ventilated work environments.

REFERENCES

ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

CFR. Code of Federal regulations. Washington, DC: U.S. Government Printing Office, Office of the Federal Register.

DOT [1993]. 1993 Emergency response guidebook, guides 12, 21. Washington, DC: U.S. Department of Transportation, Office of Hazardous Materials Transportation, Research and Special Programs Administration.

Genium [1986]. Material safety data sheet No. 61. Schenectady, NY: Genium Publishing Corporation.

Grant WM [1986]. Toxicology of the eye. 3rd ed. Springfield, IL: Charles C Thomas.

Lewis RJ, ed. [1993]. Hawley's condensed chemical dictionary. 12th ed. New York, NY: Van Nostrand Reinhold Company.

Mickelsen RL, Hall RC [1987]. A breakthrough time comparison of nitrile and neoprene glove materials produced by different glove manufacturers. Am Ind Hyg Assoc J 48(11): 941-947.

Mickelsen RL, Hall RC, Chern RT, Myers JR [1991]. Evaluation of a simple weight-loss method for determining the permeation of organic liquids through rubber films. Am Ind Hyg Assoc J 52(10): 445-447.

NFPA [1986]. Fire protection guide on hazardous materials. 9th ed. Quincy, MA: National Fire Protection Association.

NIOSH [1987a]. NIOSH guide to industrial respiratory protection. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-116.

NIOSH [1987b]. NIOSH respirator decision logic. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 87-108.

NIOSH [1995]. Registry of toxic effects of chemical substances: Nitrogen. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, Division of Standards Development and Technology Transfer, Technical Information Branch.

NLM [1995]. Hazardous substances data bank: Nitrogen. Bethesda, MD: National Library of Medicine.

Parmeggiani L [1983]. Encyclopedia of occupational health and safety. 3rd rev. ed. Geneva, Switzerland: International Labour Organisation.

Rom WN [1992]. Environmental and occupational medicine. 2nd ed. Boston, MA: Little, Brown and Company.

Sittig M [1991]. Handbook of toxic and hazardous chemicals. 3rd ed. Park Ridge, NJ: Noyes Publications.

USC. United States code. Washington. DC: U.S. Government Printing Office.

Windholz M, ed. [1983]. Merck Index 10th ed. Rahway, NJ: Merck & Company.