See if this sounds all too familiar… three (3) workers remove a manhole cover to a sanitary sewer to check for water and blockage. Unable to see anything, Employee #1 climbs down into the sewer to look for problems. A co-worker working nearby sees Employees #2 and #3 enter the manhole and comes over to check on his co-workers. He finds Employees #2 and #3 trying to revive Employee #1 down in the sewer. This employee leaves to call 911. Upon his return to the manhole, he could hear no more sounds from his co-workers. The Fire Department arrived, tested the atmosphere, and found it to be 5% Oxygen. They donned their rescue gear, made entry, and found all three (3) workers (1 entrant and 2 would-be-rescuers) deceased – presumably from the Oxygen Deficient atm.
