On February 4, 2004, a 23-year-old tank mechanic died from lack of oxygen after entering a chemical transport tank prior to a scheduled inspection.
The employer was a longtime Oregon company, based in Portland, specializing in the manufacture and maintenance of transportation tanks. At the time, the firm had 5 factories and 11 sales branches in several western states, employing over 550 workers, with about one-third in Oregon. On the day of the incident, at least two management and three coworkers were present in the vicinity of the tank department where the incident occurred.
The firm had a written confined-space entry policy, which stated, “No tank entry is permitted until the tank passes the Confined Space Pre-entry Atmospheric Check and the reclassification Confined Space Form is completed.” The OSHA investigation found that documentation was not always completed, however, and employee interviews indicated that atmospheric testing was not always performed. In late 2003, the employer trained a designated person to perform atmospheric testing on all tanks prior to entry. The individual was transferred 2 weeks prior to this incident and the duties were not reassigned.
The tank mechanic had worked for the employer since 1999, with duties that included inspecting and repairing tanks. He completed a 45-minute hazardous materials training course and test certificate in his first year, and was promoted to journeyman in 2001. Interviews by OSHA and the Medical Examiner indicated that he had been given positive performance appraisals, had never been known to bypass safety measures, and reportedly had completed “hundreds” of tank inspections similar to the one in this incident.
INVESTIGATION
On the day of the incident, the tank mechanic arrived at work at 6:30 a.m., and was told to prepare a container for dual inspection with an industry shipping inspector. About 7:45 a.m., the foreman helped the mechanic back the chemical transport truck into a bay of the tank shop. The mechanic was last seen about 45 minutes later, and was not missed until the industry inspector arrived shortly before 10 a.m.
The tank due for inspection that day was designated for the transport of silicon tetrachloride. Chemical transport tanks go through two inspections: an annual visual inspection, and a 2.5 year visual and pressure check as in this case. The visual and pressure check requires work inside the tank to verify structural integrity, and possible welding.
The tank had been purged with inert nitrogen. A dated memo posted on the outside of the tank by the owner stated:
“… this container has been washed, and is free of any hazardous materials … This container has a breathable atmosphere only when proper tank entry is followed (fresh air moved through the container and use of oxygen monitor before entering).”
The tank mechanic had placed a ladder next to the tank, opened the top manhole cover, and lowered a drop light inside. Without testing the atmosphere, he then entered the tank for an unknown reason and collapsed at the bottom of the ladder from lack of oxygen. His footprints did not extend beyond the base of the ladder. A man-hole cover at the top of the transport tank provided access into the interior.
When the inspector arrived, a coworker went looking for the tank mechanic and discovered him lying face down inside the tank. He called for help, then took a deep breath and entered the tank to retrieve the victim, without testing the atmosphere. The rescuer ran out of breath while trying to lift the victim up to others at the top of the tank, and was only able to take very shallow breaths. He emerged from the tank unharmed.
Resuscitation efforts failed, and the victim was pronounced dead by emergency responders shortly afterward. There were no injuries to indicate the victim had fallen into the tank rather than descending on his own.
Source: https://www.ohsu.edu/sites/default/files/2019-02/ORFACE-IR-Other-PermitSpace-LackofOxygen.pdf
Fire department personnel tested the atmosphere in the tank and found about 12% oxygen at the
bottom of the tank, 15% in the middle, and 17% at the top, all below the minimum safe level of
19.5% oxygen. The manhole cover had been open by then for over an hour, and ambient air raised the oxygen level at the top of the tank. Investigators found the employer’s atmospheric monitor was missing the necessary strap to reach the bottom of the tank, indicating that even had the victim tested the atmosphere with available equipment, he would have been at risk as he descended into the confined vessel.