SGT. 1ST CLASS GEORGE MCKNIGHT  
U.S. Army Central
Shaw Air Force Base
Sumter, South Carolina  

On a sunny day with the temperature in the 80s, two maintenance employees were given a work order to complete fabrication work inside a vessel to elevate pressure on the piping system. The company they worked for produced plastic chips used to make various types of containers. Portions of the system use nitrogen to push the chips through the maze of pipes for further production. The workers were located on the top floor of the building, which was seven stories high. The vessel was located on a platform another eight feet in the air.

The maintenance employees called safety personnel to inform them of their work order. They asked that someone come to the work area to perform the safety requirements and issue the permits to start the job. When the safety staff arrived, the manhole cover was removed so they could perform all necessary checks and measurements and complete the permits.

The vessel was only big enough for one of the workers, so the other employee stood watch outside for additional safety purposes. The man inside the vessel worked on the initial fabrication job for several hours, but was not able to complete it by the close of business, so he packed his tools and replaced the manhole cover in case of inclement weather.

The next day, the two workers returned to complete the job. They opened the manhole cover just as they had the previous day with no issues. Once again, one worker got into the vessel while the other prepared the gear and other work items. As the worker outside the vessel handed down some tools, he noticed his buddy had gone silent. He peeked into the vessel and saw the other worker slumped over and unconscious. The worker yelled and banged on the side of the vessel in an attempt to revive his buddy. He then tried to reach into the vessel to grab him, but his body was too big to get far enough inside.

As panic set in, the worker ran to the nearby emergency phone to call for help. Their supervisor was the first one the scene, running up seven flights of stairs and not knowing what he would encounter. When he arrived, the panicked worker explained what happened. Fortunately, the supervisor was small enough to get into the vessel and reach the unconscious employee. Soon, though, the supervisor also passed out as the man outside the vessel looked on helplessly.

Safety personnel arrived shortly afterward, connected an emergency safety airline and stuck it into the vessel. As oxygen was pushed into the vessel, the supervisor awoke — groggy and disoriented but fully aware of his surroundings. The safety personnel tried to pull out the supervisor, but he was just out of their reach. They then threw down a rope, which the supervisor tied around the unconscious maintenance worker before climbing up and out of the vessel and passing out again. After a couple of attempts, the unconscious maintenance employee was also pulled to safety and the two men were transported to a hospital for medical attention. Fortunately, both survived.

Afterward, the safety personnel confirmed the cause of the mishap. While the manhole cover was closed overnight, nitrogen seeped from a non-air-tight valve and displaced the oxygen content of air. This caused the maintenance worker and his supervisor to fall unconscious when they entered the vessel.

When the vessel was checked by safety personnel to confirm it could be safely entered for maintenance, that measurement and permit were only good for that particular day. If work is not completed within that day, all of the safety checks must be conducted again before work can resume inside. There should also be a device inside the confined space to continuously monitor the air quality. In addition, ventilator fans can provide extra protection by ensuring a steady oxygen flow inside the vessel.

If you ever find yourself in a similar situation, resist the urge to go inside the confined space to attempt a rescue. The air quality could be hazardous and result in you, too, being rendered unconscious. It’s always best to call for help immediately and monitor the situation from the outside.

FYI
For more information on preventing confined space mishaps, visit the U.S. Army Combat Readiness Center’s workplace safety website at https://safety.army.mil/ON-DUTY/Workplace/Confined-Space.