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Chemical Sampling Information (CSI)
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General Description

Synonyms: Dinitrogen monoxide; Hyponitrous acid anhydride; Laughing gas; Nitrogen oxide

OSHA IMIS Code Number: 1953

Chemical Abstracts Service (CAS) Registry Number: 10024-97-2

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: QX1350000

Department of Transportation Regulation Number (49 CFR 172.101) and Guide: 1070 122; 2201 122 (refrigerated liquid)

NIOSH Pocket Guide to Chemical Hazards, Nitrous oxide: chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

OSHA Permissible Exposure Limit (PEL):

Construction Industry: 29 CFR 1926.55 Appendix A -- Simple asphyxiants. The limiting factor is the available oxygen which shall be at least 19.5% and be within the requirements addressing explosion in part 1926.

Maritime: 29 CFR 1915.1000 Table Z-Shipyards -- Simple asphyxiants. The limiting factor is the available oxygen which shall be at least 18 percent and be within the requirements addressing explosion in subpart B of part 1915.

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 50 ppm, 90 mg/m3 TWA; Appendix A4 - Not Classifiable as a Human Carcinogen

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 25 ppm, 46 mg/m3 TWA over the time exposed. [Note: REL for exposure to waste anesthetic gas.]

Health Factors

Carcinogenic Classification:

International Agency for Research on Cancer (IARC): Anaesthetics, volatile - Group 3, not classifiable as to its carcinogenicity to humans [1 MB PDF, 454 pages]

Potential Symptoms: Dyspnea; euphoria, drowsiness; headache; asphyxia; reproductive effects; frostbite (from contact with liquid), lowering of consciousness.

Health Effects: Reproductive Hazard (Male and Female) (HE5); CNS effects (HE7); Asphyxiant (HE17); Bone marrow depression (HE12). <

Affected Organs: Respiratory system, CNS, peripheral nervous system, reproductive system


  1. OSHA does not have a PEL for nitrous oxide. [See also Waste Anesthetic Gases.]
  2. Occupational exposure to nitrous oxide is primarily via its use in anesthesia and analgesia by health care personnel.
  3. Nitrous oxide is a drug of abuse by inhalation and has caused a number of deaths from asphyxia.
  4. Long-term exposure to nitrous oxide can result in some symptoms of pernicious anemia: megaloblastic bone-marrow depression or peripheral and central neuropathy (tingling, numbness, impairment of equilibrium, difficulty in thinking clearly).
  5. These symptoms result from the inhibition of methionine synthase by the nitrous oxide-induced inactivation of the reduced form of vitamin B12.

Literature Basis:

  • NIOSH Pocket Guide to Chemical Hazards: Nitrous oxide.
  • International Chemical Safety Cards (WHO/IPCS/ILO): Nitrous oxide.
  • Pohanish, R.P. (editor): Nitrous Oxide. In, Sittig’s Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 2. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1748-1749.
  • Rowland, A.S., Baird, D.D., Shore, D.L., Weinberg, C.R., Savitz, D.A. and Wilcox, A.J.: Nitrous oxide and spontaneous abortion in female dental assistants. Am. J. Epidemiol. 141(6): 531-538, 1995.
  • Suruda, A.J. and McGlothlin, J.D.: Fatal abuse of nitrous oxide in the workplace. J. Occup. Med. 32(8): 682-684, 1990.
  • Weimann, J.: Toxicity of nitrous oxide. Best Pract. Res. Clin. Anaesthesiol. 17(1): 47-61, 2003.

Date Last Revised: 05/30/2007

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: VAPOR-TRAK Nitrous Oxide Monitor
    maximum time: 16 Hours
    minimum time: 15 Minutes
    current analytical method: Infrared; IL33
    method reference: Follow Manufacturer's Instruction Sheet. The Salt Lake Technical Center has not evaluated this product.
    method classification: Not Validated
    note: Analysis performed by manufacturer of badge. Badges are sent to the OSHA Technical Center. The Salt Lake Technical Center has not evaluated this product. CSHO's should consult OSHA instruction CPL 2-2.60 prior to taking any samples where exposure to bloodborne pathogens could occur.

  • sampling media: Five Layer Aluminized Gas Sampling Bag (5 liter)
    maximum volume: 5 Liters
    maximum flow rate: 0.05 L/min
    current analytical method: Infrared; IL52
    method reference: OSHA In-House File
    method classification: Not Validated

Laboratory Sampling/Analytical Method (Wisconsin OHL):

  • sampling media: Evacuated Cans - Back Filled with Nitrogen (Hold button down for a full 10 seconds)
    maximum volume: 120 mLiters
    current analytical method: Mass Spectrometry; GC/MS
    method reference: (WOHL In-House File)
    method classification: Not Validated
    note: Call WOHL for instructions and evacuated cans

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