Fatality Case Shows Dangers of Deep Confined Spaces An AIHce EXP 2018 session presenter analyzed a 2012 fatality inside a sewer valve vault that was 18 feet, 6 inches deep. May 29, 2018 PHILADELPHIA -- This year's "Notable Confined Spaces" sessions on May 23 at the AIHce EXP conference, put on by the AIHA Confined Spaces Committee, included a report about one fatal incident and a discussion of how liquid hydrocarbon storage tanks with internal floating roofs can be safely entered for cleaning and maintenance. Presenters were Bonnie Lockhart, CIH, with Ameren Corp., and Jay Gieseke, CIH, CSP, with Andeavor's St. Paul Park refinery in Minnesota. Lockhart discussed an Aug. 28, 2012, fatal incident where a 53-year-old worker died. He was engaged in cleaning and coating surfaces inside several vertically entered confined spaces at a remote site, using the solvent MEK -- methyl ethyl ketone -- for cleaning and painting inside the spaces. At the time of the accident, one other person, a supervisor, was on site, sitting in a truck with the air conditioner running about 300 feet away from the sewer valve vault where the worker died, she said. The worker had worked in five of the other spaces the day before, all of them 7-10 feet deep. But this vault was 18 feet, 6 inches deep, which must have surprised the worker because he had brought his 8-foot ladder to the site that day, apparently expecting the sixth space to be the same depth, she said. When the supervisor checked on the worker, he had collapsed at the bottom of the vault. Firefighters were summoned and retrieved the fallen worker; the firefighters ventilated the space, and Lockhart said at least 1,000 air changes occurred in the space during the retrieval process. There was no entry permit prepared, no air sampling done (either pre-entry or continuous), no attendant on duty, no retrieval equipment on hand, and no ventilation of the space conducted for the worker's entry. Two days after his death, a reading of 1,800-1,900 ppm of MEK was taken in the space, more than three times higher than the IDLH of 500 ppm for the solvent, Lockhart said. The cause of death determined in the case was acute MEK toxicity, but Lockhart said she concluded that acute multiple solvent toxicity was the cause because the mixture he was using included other hazardous chemicals. She explained that the rungs in the side of the vault were difficult to access, and it's likely that some of his mixture spilled to the bottom as he reached for the first rungs. The victim's urine and blood indicated he'd been exposed to extremely high levels of MEK. She explained that her research, aided by personnel from an OSHA facility in Salt Lake City, showed very small amounts of MEK would produce an IDLH atmosphere at the 18-foot, 6-inch depth of the vault.