The Hazards of Nitrogen Asphyxiation

To combat these needless deaths, the CSB provided very useful training information for workers who may be exposed to hazardous nitrogen atmospheres. This valuable information is available in three different forms that can be downloaded from their website. They have a one-page tri-fold brochure entitled, Nitrogen-Enriched Atmospheres Can Kill For the more seri- 

Hazards of Nitrogen Asphyxiation provides a number of case studies and highlights good safety practices. The bulletin indicates that failure to detect an oxygen-deficient (nitrogen-enriched) atmosphere was a significant factor in case studies. Many of the incidents involved a situation in which personnel were in or around a confined area, such as a rail-car, room, or tank. The safety bulletin includes a chart on the effects of oxygen deficiency on the human body. [7] Several critical points from that chart are shown below  

At oxygen concentrations of 16.0%, the possible results to humans include increased pulse and breathing rate, impaired thinking and attention, and reduced coordination. 

In atmospheres in which the oxygen content is 14.0%, the possible results include abnormal fatigue upon exertion, faulty coordination, poor judgment, etc. 

At oxygen concentrations of 12.5%, the possible results to humans include very poor judgment and coordination, impaired respiration that may cause permanent heart damage, nausea, and vomiting. 

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In its safety bulletin on the hazards of nitrogen asphyxiation, CSB identified 80 nitrogen asphyxiation deaths and 50 injuries occurring in 85 incidents between 1992 and 2002 (CSB, Hazards of Nitrogen Asphyxiation, Safety Bulletin no. 2003-10-B, 2003). 

Asphyxiation and Toxicity Hazards An asphyxiant is a chemical (either a gas or a vapor) that can cause death or unconsciousness by suffocation (BP, Hazards of Nitrogen and Catalyst Handling, 2003). A simple asphyxiant is a chemical, such as N2, He, or Ar, whose effects are caused by the displacement of 02 in air, reducing the 02 concentration below its normal value of approximately 21 vol %. The physiological effects of oxygen concentration reduction by simple asphyxiants are illustrated in Table 23-18 (BP, Hazards of Nitrogen and Catalyst Handling, 2003). 

Injuries and fatalities from asphyxiation are often associated with personnel entry into inerted equipment or enclosures. Guidance on safe procedures for confined space access are provided by OSHA (OSHA, 29 CFR 1910.146, Confined Space Entry Standard, 2000), the American National Standards Institute (ANSI, Z117.1, Safety Requirements for Confined Spaces, 2003), Hodson (Hodson, Safe Entry into Confined Spaces, Handbook of Chemical Health and Safety, American Chemical Society, 2001), and BP (BP, Hazards of Nitrogen and Catalyst Handling, 2003). OSHA has established 19.5 vol % as the minimum safe oxygen concentration for confined space entry without supplemental oxygen supply (see Table 23-18). Note that OSHA imposes a safe upper limit on 02 concentration of 23.5 vol % to protect against the enhanced flammability hazards associated with 02-enriched atmospheres. 

It is important not only to consider the hazards associated with the low temperatures of cryogens, but to remember that each cryogen itself may have other hazardous properties specifle to that particular chemical. Liquid nitrogen and liquid helium present only asphyxiation hazards as gases while carbon... 

Inhalation. Nitrogen is generally inert and can cause asphyxiation due to displacement of oxygen in the atmosphere. Rescuers wearing an SCBA or air-line respirators should move the affected person from the hazardous exposure to fresh air at once. If supplemental oxygen is available, administer by nasal canula or mask. Perform artificial respiration if the person is not breathing. Persons who have been unconscious should be taken to a hospital for evaluation and care. 

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