World Library  
Flag as Inappropriate
Email this Article

Asphyxiant gas

Article Id: WHEBN0007276747
Reproduction Date:

Title: Asphyxiant gas  
Author: World Heritage Encyclopedia
Language: English
Subject: Inert gas asphyxiation, Argon, Blackdamp, Davy lamp, Toxicology
Collection: Toxicology
Publisher: World Heritage Encyclopedia

Asphyxiant gas

An Asphyxiant gas is a nontoxic or minimally toxic gas which reduces or displaces the normal oxygen concentration in breathing air. Breathing of oxygen-depleted air can lead to death by asphyxiation (suffocation). Because asphyxiant gases are relatively inert and odorless, their presence in high concentration may not be noticed, except in the case of carbon dioxide (hypercapnia).

Toxic gases, by contrast, cause death by other mechanisms, such as competing with oxygen on the cellular level (e.g., carbon monoxide) or directly damaging the respiratory system (e.g., phosgene). Far smaller quantities of these are deadly.

Notable examples of asphyxiant gases are nitrogen, argon, helium, butane and propane. Along with trace gases such as carbon dioxide and ozone, these compose 79% of Earth's atmosphere. The atmosphere is mostly harmless because the remaining 21% is O2.


  • Asphyxia hazard 1
  • Risk management 2
    • United States 2.1
      • Odorized gas 2.1.1
  • In mining 3
  • See also 4
  • References 5

Asphyxia hazard

Asphyxiant gases in the breathing air are normally not hazardous. Only where elevated concentrations of asphyxiant gases displace the normal oxygen concentration a hazard exists. Examples are:

Risk management

The risk of breathing asphyxiant gases is frequently underestimated leading to fatalities, typically from breathing helium in domestic circumstances and nitrogen in industrial environments.[13]

The term asphyxiation is often mistakenly associated with the strong desire to breathe that occurs if breathing is prevented. This desire is stimulated from increasing levels of carbon dioxide. However, asphyxiant gases may displace carbon dioxide along with oxygen, preventing the victim from feeling short of breath. In addition the gases may also displace oxygen from cells, leading to loss of consciousness and death rapidly.

United States

The handling of compressed asphyxiant gases and the determination of appropriate environment for their use is regulated in the United States by the Occupational Safety and Health Administration (OSHA). The National Institute for Occupational Safety and Health (NIOSH) has an advisory role.[14] OSHA requires employers who send workers into areas where the oxygen concentration is known or expected to be less than 19.5% to follow the provision of the Respiratory Protection Standard [29 CFR 1910.134]. Generally, work in an oxygen depleted environment requires an SCBA or airline respirator. The regulation also requires 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."[15] Containers should be labeled according to OSHA's Hazard Communication Standard [29 CFR 1910.1200]. These regulations were developed in accordance with the official recommendations of the Compressed Gas Association (CGA) pamphlet P-1. The specific guidelines for prevention of asphyxiation due to displacement of oxygen by asphyxiant gases is covered under CGA's pamphlet SB-2, Oxygen-Deficient Atmospheres.[16] Specific guidelines for use of gases other than air in back-up respirators is covered in pamphlet SB-28, Safety of Instrument Air Systems Backed Up by Gases Other Than Air.[17]

Odorized gas

To decrease the risk of asphyxiation, there have been proposals to add warning odors to some commonly used gases such as nitrogen and argon. However, CGA has argued against this practice. They are concerned that odorizing may decrease worker vigilance, not everyone can smell the odorants, and assigning a different smell to each gas may be impractical. Another difficulty is that most odorants (e.g., the thiols) are chemically reactive. This is not a problem with natural gas burned as a fuel, but a major use of asphyxiants such as nitrogen, helium, argon and krypton is to protect reactive materials from the atmosphere.[18][19]

In mining

The dangers of excess concentrations of nontoxic gases has been recognized for centuries within the mining industry. The concepts of black damp (or "stythe") and afterdamp reflect an understanding that certain gaseous mixtures could lead to death with prolonged exposure.[20] Early mining deaths due to mining fires and explosions were often a result of encroaching asphyxiant gases as the fires consumed available oxygen. Early self-contained respirators were designed by mining engineers such as Henry Fleuss to help in rescue efforts after fires and floods. While canaries were typically used to detect carbon monoxide, tools such as the Davy lamp and the Geordie lamp were useful for detecting methane and carbon dioxide, two asphyxiant gases. When methane was present, the lamp would burn higher; when carbon dioxide was present, the lamp would gutter or extinguish. Modern methods to detect asphyxiant gases in mines led to the Federal Mine Safety and Health Act of 1977 in the United States which established ventilation standards in which mines should be "...ventilated by a current of air containing not less than 19.5 volume per centum of oxygen, not more than 0.5 volume per centum of carbon dioxide..."[21]

See also


  1. ^ Terazawa K, Takatori T, Tomii S, Nakano K. Methane asphyxia. Coal mine accident investigation of distribution of gas. Am J Forensic Med Pathol. 1985 Sep;6(3):211-4. PMID 3870672
  2. ^ Discussion of the Kursk disaster and death on submarines
  3. ^ Kirk JC. Proposed minimum requirements for the operational characteristics and testing of submersible atmosphere monitoring and control units. Life Support Biosph Sci. 1998;5(3):287-94. PMID 11876195
  4. ^ a b Gill JR, Ely SF, Hua Z.Environmental gas displacement: three accidental deaths in the workplace. Am J Forensic Med Pathol. 2002 Mar;23(1):26-30. PMID 11953489
  5. ^ Sahli BP, Armstrong CW.Confined space fatalities in Virginia. J Occup Med. 1992 Sep;34(9):910-7. PMID 1447597
  6. ^ BBC article on the Lake Nyos incident
  7. ^ Yoshitome K, Ishikawa T, Inagaki S, Yamamoto Y, Miyaishi S, Ishizu H. A case of suffocation by an advertising balloon filled with pure helium gas. Acta Med Okayama. 2002 Feb;56(1):53-5. PMID 11873946
  8. ^
  9. ^ OSHA article on asphyxiant gases accidentally fed into respirators
  10. ^ Gallagher KE, Smith DM, Mellen PF. Suicidal asphyxiation by using pure helium gas: case report, review, and discussion of the influence of the internet. Am J Forensic Med Pathol. 2003 Dec;24(4):361-3. PMID 14634476
  11. ^ Gilson T, Parks BO, Porterfield CM. Suicide with inert gases: addendum to Final Exit. Am J Forensic Med Pathol. 2003 Sep;24(3):306-8. PMID 12960671
  12. ^ Shields LB, Hunsaker DM, Hunsaker JC 3rd, Wetli CV, Hutchins KD, Holmes RM. Atypical autoerotic death: part II. Am J Forensic Med Pathol. 2005 Mar;26(1):53-62. PMID 15725777
  13. ^ BBC Family of 'helium death' teen warn of inhalation
  14. ^ 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.
  15. ^ OSHA page for nitrogen, a representative asphyxiant gas
  16. ^ Link to pamphlet SB-2
  17. ^ Link to pamphlet SB-28
  18. ^ [1] Summary of CGA position on odorizing. Accessed 10/11/06
  19. ^ [2] Full text of CGA position on odorizing. Accessed 10/11/06
  20. ^ Mine Safety and Heath Administration article about mine fire survival. Accessed 10/12/06
  21. ^ MSHA copy of the Mine Act of 1977. Accessed 10/12/06
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.