Board Releases Safety Bulletin on Nitrogen Asphyxiation Hazards, Underscores Need for Good Safety Practices

June 25, 2003
Washington, DC - June 25, 2003) Reporting that nitrogen asphyxiation has caused 80 fatalities in the U.S. over the last decade, the U.S. Chemical Safety and Hazard Investigation Board (CSB) today released a new safety bulletin that presents a series of good safety practices to prevent nitrogen-related incidents.

"While nitrogen makes up the majority of the air we breathe and is not toxic, people shouldn't assume it's benign," according to CSB Chairman Carolyn W. Merritt. "Nitrogen does not support life, and when nitrogen displaces the oxygen we breathe, it can prove very deadly. Since nitrogen is odorless and colorless, our senses provide no protection against nitrogen-enriched atmospheres. Good safety management practices are essential if we are to reduce the annual toll of nitrogen-related deaths and injuries."

In addition to the full safety bulletin, the CSB has developed a one-page safety brochure and a downloadable Powerpoint® presentation on nitrogen hazards. The safety brochure and slide presentation provide useful training information for workers who may be exposed to hazardous nitrogen atmospheres. Free copies of the bulletin, brochure, and presentation are available from the agency website,, or by contacting the agency at (202) 261-7600.

Nitrogen is an inert gas, which means that it does not react with other chemicals under most normal circumstances. Nitrogen is often used in industrial settings to displace other gases that are toxic, corrosive, reactive, or present fire or explosion hazards, making processes safer. Using nitrogen to remove oxygen from process equipment decreases the chances of a fire or explosion, but it also can make the atmosphere in and around the equipment hazardous for humans to breathe.

As part of this project, the CSB reviewed a number of nitrogen asphyxiation incidents that have occurred in the past decade. Findings from this study included the following:

- 85 incidents occurred in the past decade that resulted in an average of 8 deaths and 5 injuries each year;

- Causes of the incidents included personnel not knowing they were entering an oxygen-depleted environment or not realizing that the environment had changed, and also mistaking nitrogen gas for breathing air;

- Incidents occurred in a variety of settings including chemical plants, food processing and storage facilities, laboratories, and medical facilities;

- Almost half the incidents and over 60% of the fatalities involved contractors, including construction workers;

- A number of deaths were caused by personnel attempting rescue without proper training and equipment.

Several good practices are highlighted in the bulletin to address the causes of incidents. Also, a number of case studies are presented, including one that occurred in a nursing home that resulted in the death of four patients. The bulletin follows a 1998 CSB investigation of a nitrogen asphyxiation incident that occurred in a temporary enclosure at the then-Union Carbide plant in Hahnville, Louisiana. Acting upon a recommendation from the CSB, the U.S. Occupational Safety and Health Administration (OSHA) issued a bulletin in 2002 on the use of temporary enclosures. Another CSB recommendation from that case -- that the National Institute for Occupational Safety and Health (NIOSH) study the feasibility of odorizing nitrogen - awaits further action.

The CSB is an independent federal agency established in 1998 with the mission of protecting workers, the public, and the environment by investigating and preventing chemical accidents. The CSB determines the root causes of these accidents and makes safety recommendations to government agencies, companies, and other organizations. The CSB issues accident investigation reports, hazard investigations, safety bulletins, and other safety products.

For more information visit or contact Stephen J. Wallace at 202-261-7612.

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