Safety board issues safety bulletin that addresses nitrogen asphyxiation

Sept. 1, 2003
A SAFETY bulletin that addresses nitrogen asphyxiation has been released by the Chemical Safety and Hazard Investigation Board (CSB). The CSB issued the

A SAFETY bulletin that addresses nitrogen asphyxiation has been released by the Chemical Safety and Hazard Investigation Board (CSB). The CSB issued the bulletin, noting that 80 fatal asphyxiations have occurred over the last 10 years.

Numerous deaths have been reported over the years at tank cleaning facilities and tank truck carrier terminals. Both food-grade and chemical operations have been affected. News reports of these accidents are all too common, those familiar with the industry say.

The CSB report notes that a number of deaths resulted when workers attempted to rescue others without proper training and equipment.

The bulletin presents a series of good safety practices to prevent nitrogen-related incidents. The bulletin also contains a brochure and slide presentation for use in training sessions for workers who may be exposed to hazardous nitrogen atmospheres.

“While nitrogen makes up the majority of the air we breathe and is not toxic, people shouldn't assume it's benign,” Carolyn Merritt, CSB chairman said. “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.”

Nitrogen, an inert gas, does not react with other chemicals under most normal circumstances, and is often used in industrial settings to displace other gases that are toxic, corrosive, reactive, or present fire or explosion hazards.

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:

  • 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 case studies are presented in the bulletin, 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 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.

More information can be found on the CSB Web site at csb.gov.

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