Don't Normalise deviations!

 In 1994, a fatality caused by exposure to hydrogen sulfide occurred at a refinery. The accident  occurred while draining of a fuel gas knockout drum in a hydro treating unit. Normal work procedures included periodically opening a valve that carried a water-gas mixture to a separator which removed and vented hydrocarbon gases to a flare. During the preceding winter, the piping to the separator froze, and the drum was temporarily drained to the sewer. This deviation went unnoticed and the temporary practice of draining to the sewer continued. On the day of the incident, the operator opened the valve to the sewer believing it to be part of the draining procedure, resulting in the release of toxic amounts of hydrogen sulfide that killed the operator.

Source: osha.gov

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