Union Carbide Corp. Nitrogen Asphyxiation Incident

On March 27, 1998, one worker was killed and another severely injured when they were asphyxiated by nitrogen, an odourless gas that was venting through the large open pipe where the men were working at Union Carbide’s Taft/Star plant in Hahnville, Louisiana. The Taft plant manufactures industrial chemicals, and the accident occurred in the plant’s ethylene oxide production unit.

The ethylene oxide unit was undergoing a major maintenance project, in which some process equipment had been temporarily removed. The equipment removal left the pipe connected into the process unit but open to the air at one end. The two victims, both skilled and experienced workers, were inspecting the inside of the 48-inch open pipe end to gauge the effectiveness of an earlier cleaning effort. While the men worked, nitrogen gas was being used to purge air and moisture from the unit, protecting the chemicals inside.

During their inspection of the inside of the pipe, the two workers used a black light, which causes grease, oil, and other contaminants to glow in the dark. But the midday sun would make it difficult to see, so the workers asked two contractors to hold a black plastic sheet over the open pipe end while they crouched just inside. Unknown to any of the workers, the plastic sheet created a dangerous enclosure where nitrogen gas could accumulate, displacing oxygen and causing asphyxiation.

The two contract workers holding the sheet became concerned when they had not heard from the workers inside for some 15 minutes. When there was no response to their calls, they pulled the sheet away and found one worker unconscious and the other in a daze. The first worker was pronounced dead on arrival at a hospital.

The second man was hospitalized in critical condition but survived. The U.S. Chemical Safety Board investigated the accident and found that inadequate confined-space warnings and entry procedures were at the root of the tragedy.