Confined Space Accident at Chemical Plant Leaves One Dead, One Injured

Hahnville, LA -- A routine inspection of a pipe at the Union Carbide Taft/Star Manufacturing Plant in Hahnville, LA turned deadly when two workers were overcome due to nitrogen asphyxiation. One plant worker was killed and an independent contractor was seriously injured when nitrogen gas was trapped and failed to vent safely.

The plant, which produces chemicals for industry, is located about 30 miles west of New Orleans. The incident occurred in the plant's Taft Oxide I Unit, which primarily produces ethylene oxide, ethylene glycol, and glycol ethers. At the time of the incident, the Unit had been closed for maintenance for about six weeks while workers replaced equipment and cleaned an oxygen feed mixer.

At approximately 12:15 pm, workers on the fifth level of the structure, approximately 60 feet above the ground, were performing a black light inspection at an open end of a 48-inch-wide horizontal pipe, which had been opened for the purpose of maintenance. The two open pipe ends were wrapped with clear plastic sheeting in order to keep the pipe free of debris until the oxygen feed mixer was reinstalled. Nitrogen was being injected into the process equipment to protect new catalyst in reactors from exposure to moisture. The nitrogen was also flowing through some of the piping systems connected to the reactors. The nitrogen was venting from one side of the open pipe where formerly it had been connected to an oxygen feed mixer. No warning sign was posted on the pipe opening identifying it as a confined space or warning that the pipe contained potentially hazardous nitrogen.

No warning sign was posted on the pipe opening identifying it as a confined space or warning that the pipe contained potentially hazardous nitrogen.

Nitrogen is an odorless, tasteless, and invisible gas that can cause asphyxiation at high concentrations. When used in confined spaces, nitrogen is especially hazardous because it cannot be detected by human senses but can cause injury or death within minutes by displacing oxygen within the bloodstream.

The two workers had secured a sheet of black plastic over the end of the pipe where they were working to provide shade to make it easier to conduct the black light test during daylight. While working just outside the pipe opening and inside of the black plastic sheet, the two workers were apparently overcome by nitrogen. At approximately 12:20 pm, a contractor noticed blood on one of the worker's hands when he looked through a gap in the plastic sheet. He alerted his foreman. The foreman called to the two workers behind the sheet and, getting no reply, removed the sheet.

Witnesses said that one worker was found in front of the pipe, unconscious and slumped over with his head lying inside the open pipe. The other was found seated beside the pipe opening, dazed and leaning against the side of the pipe.

The plant emergency response team arrived and removed the two men from the scene and administered cardiopulmonary resuscitation. The two workers were transported by ambulance to St. Charles Parish Hospital. One man was dead on arrival; the other was admitted to the hospital in critical condition and given oxygen therapy over the next several days. He was released after five days in the hospital.

Above photo is from Emergency Film Group's program Confined Space Emergency."

OSHA defines a confined space as a space that is large enough to enter, has limited or restricted means for entry or exit, and has not been designed for continuous human occupancy. One factor that makes entering a confined space hazardous is that the space may contain a hazardous atmosphere. A confined space may contain a toxic gas, such as hydrogen sulfide, in concentrations hazardous to health. Other confined spaces may contain a nontoxic gas, such as nitrogen, in concentrations that displace the oxygen in the air in the space. The air we normally breathe contains about 21% oxygen, 78% nitrogen, and trace amounts of other gases. In this incident, the nitrogen acted as an asphyxiant, causing suffocation by displacing oxygen-containing air.

It is not necessary for nitrogen to displace all of the 21% of oxygen normally found in the air in order to cause harm to people. OSHA requires that oxygen levels be maintained at or above 19.5% in order to prevent injury to workers. According to the Compressed Gas Association, "exposure to atmospheres containing 8-10 percent or less oxygen will bring about unconsciousness without warning and so quickly that the individuals cannot help or protect themselves." Exposure to an atmosphere containing 6-8 percent oxygen can be fatal in as little as 6 minutes. Exposure to an atmosphere containing 4-6 percent oxygen can result in a coma in 40 seconds and subsequent death.