The United States Chemical Safety and Hazard Investigation Board (CSB) is an independent Federal agency whose mission is to ensure the safety of workers, the public, and the environment by investigating and preventing chemical incidents. In 1998, CSB investigated a nitrogen asphyxiation incident that occurred in Hahnville, Louisiana, in which one worker died and a contractor was seriously injured. As a result of that investigation, CSB began informally tracking the prevalence of these types of incidents. Based on this effort, CSB determined that nitrogen asphyxiation is a serious problem in the chemical industry and developed a safety bulletin as an educational tool to help prevent such incidents in the future. This bulletin, a downloadable PowerPoint presentation, and a 1-page flyer are available at www.csb.gov.
Every year people are killed from breathing "air" that contains too little oxygen. Because 78 percent of the air we breathe is nitrogen gas, many people assume that nitrogen is not harmful. However, nitrogen is safe to breath only if it is mixed with an appropriate amount of oxygen. These two gases cannot be detected by the sense of smell. A nitrogen-enriched environment, which depletes oxygen, can be detected only with special instrumentation. If the concentration of nitrogen is too high (and oxygen too low), the body becomes oxygen deprived and asphyxiation occurs.
This Safety Bulletin is published to bring additional attention to the continuing hazards of nitrogen asphyxiation: Nitrogen is widely used commercially and is often used to keep material free of contaminants (such as oxygen) that may corrode equipment or be flammable or toxic; Nitrogen asphyxiation hazards in industry have accounted for 80 deaths over the last 10 years. These incidents occurred in a variety of facilities including industrial plants, laboratories, and medical facilities; almost half involved contractors; and Good practices and awareness of hazards minimize the risk of nitrogen asphyxiation. nitrogen is safe to breath
Many incidents reviewed by CSB while developing this bulletin were caused by inadequate knowledge of the hazard or inadvertent use of nitrogen rather than breathing-air delivery systems.
Although the use of nitrogen presents other hazards, such as cryogenic hazards from liquid nitrogen and hazards from high-pressure nitrogen, this bulletin focuses only on the hazard of asphyxiation.
One of the most important commercial uses of nitrogen is as an inerting agent to improve safety. Nitrogen is inert under most conditions (meaning that it does not react with or affect other material). It is often used to keep material free of contaminants, including oxygen-which can present a fire and explosion hazard when in contact with flammable materials or corrode equipment. In such cases, a flow of nitrogen is maintained in a vessel to keep oxygen out. Nitrogen is also used to purge air from equipment prior to introducing material or to purge flammable and toxic material from equipment prior to opening it for maintenance.
