Nitrogen hazards of asphyxiation

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). 

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 ... 

U.S. Chemical Safety and Hazard Investigation Board, Hazards of Nitrogen Asphyxiation, Safety Bulletin No 2003-10-B, June 2003. 

Compressed Gas Association, 2001. Found in U.S. Chemical Safety Hazard Investigation Board. Safety Bulletin. Hazards of Nitrogen Asphyxiation available at http //www.csb.gov/assets/document/SB-Nitrogen-6-ll-03.pdf (accessed September 14, 2009). 

To combat these needless deaths, the CSB provided very useM training infonna-tion for workers who may be exposed to hazardous nitrogen atmospheres. This valuable information is available in different forms that can be downloaded from then-website. They have a one-page trifold brochure entitled, Nitrogen-Enriched Atmospheres Can Kill There is also a 10-page safety bulletin entitled. Hazards of Nitrogen Asphyxiation, No. 2003-10-B, June 2003 [7]. 

No Escape Dangers of Confined Spaces or Hazards of Nitrogen Asphyxiation. 

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. 

Provide nitrogen backup to instrument air (caution be aware of potential asphyxiation hazards)... 

Workers must be aware that nitrogen and other inert gases are hazardous and can quickly and easily cause asphyxiation. People working near leaking flanges have been affected (210) a burst of nitrogen can cause a fatality. Detailed discussion is presented elsewhere (210). 

Argon (87.4 K) is the most plentiful of the rare gases, but makes up only about 1% of the earth s atmosphere. It is inert, so safety is not a hazard except for asphyxiation. It is not often used because nitrogen is both colder and cheaper - if a temperature of 87 K is needed, it is relatively easy to use LN as a coolant and heat the object above LN temperature. 

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