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Municipal water system operator dies after entering oxygen-deficient valve vault in Montana, May 23, 1991.
Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, FACE 91-17, 1991 Dec; :1-11
The case of a 35 year old male water system operator who died after entering a valve vault at a municipal water system facility was examined. The employer was a municipal public utilities department that had 98 employees and a written safety policy, safety program and established safe work procedures. The worker planned to open a valve on a water line serving a nearby tree farm. The valves on this line were inside a 7 foot deep, 6 foot diameter concrete valve vault below ground at the water treatment facility. The victim apparently entered the vault without testing or ventilating the atmosphere, which was later found to be oxygen deficient. He was apparently overcome and fell to the bottom of the vault. He was found lying at the bottom of the vault about 1 hour later. The cause of death was asphyxia due to oxygen displacement. The atmosphere in the vault was found to have as little as 2% oxygen when subsequently tested. Police officers investigating the incident attempted to enter the vault later the same day, but had trouble breathing. It was recommended that employers recognize that confined space atmospheres are dynamic environments and all written safe work procedures and worker training should emphasize this fact. Police, fire and rescue personnel should be trained in confined space entry and rescue.
NIOSH-Author; Region-8; FACE-91-17; Accident-analysis; Confined-spaces; Air-quality-monitoring; Air-sampling; Work-practices; Oxygen-deficient-atmospheres
Field Studies; Fatality Assessment and Control Evaluation
NTIS Accession No.
National Institute for Occupational Safety and Health
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division