Coroner Identifies Gas in Deaths : Accident: Report says three Rincon oil rig workers succumbed to lethal doses of carbon monoxide, not hydrogen sulfide, as first thought.

Three workers killed in a Rincon oil rig accident last week died after inhaling toxic levels of carbon monoxide gas, the Ventura County coroner’s office said Friday.

Authorities originally suspected that the workers were killed after breathing lethal doses of hydrogen sulfide, a colorless gas sometimes found in oil fields.

But the coroner’s report appears to debunk that theory. In a short news release, Chief Medical Examiner Ronald L. O’Halloran said preliminary analyses show that all three victims had lethal levels of carbon monoxide in their blood.

“At this time there is no indication that hydrogen sulfide gas played a role in their deaths,� he said.

Nevertheless, blood samples have been sent to a consulting lab for further tests for hydrogen sulfide. The workers’ cause of death will not be final until those results are back in several weeks, coroner’s officials said.

Carbon monoxide is a colorless, odorless gas emitted from car tailpipes and other sources of fire. It can attain lethal levels in enclosed spaces.

Cigarette smoking causes the largest human exposure to carbon monoxide, experts say. The gas kills by depriving the body of oxygen, causing quick deterioration of vital organs such as the brain and heart.

Mike Furrow, vice president of Pride Petroleum, which employed the three men who died, said the coroner’s findings will shift the focus of his company’s investigation to the possible source of the carbon monoxide.

The only combustion engine running at the time of the Aug. 10 accident was a small truck motor owned by Schlumberger Well Services, Furrow said. But it is rare for emissions from a single engine to cause problems because carbon monoxide gas dissipates quickly in open-air pits, such as the one in which the victims were working, he said.

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Some rig operations require the use of up to eight engines at one time, with no problems from carbon monoxide fumes, Furrow said.

“To my knowledge, I’ve never heard of a carbon monoxide poisoning in any case,� he said. “We’re really at a loss as to what could have been the source of the carbon monoxide.�

Schlumberger officials were not available for comment Friday. Nor were executives at Vintage Petroleum, the Tulsa, Okla.-based oil company that hired contractors Pride and Schlumberger to do the drilling.

But a state safety official said he also found the coroner’s report puzzling.

There has not been a single fatality from carbon monoxide poisoning in the oil industry statewide for the past 10 years, said John Duncan, who is spearheading an investigation for California Occupational Safety and Health Administration.

Still, Cal/OSHA investigators are not ruling out any possible cause for the deaths, including hydrogen sulfide poisoning, until their investigation is complete in about a month, Duncan said.

Pride workers Sean Harris, Jason Hoskins and Ronald Johnson were killed while working in a pit at the wellhead of a defunct rig near Seacliff. The men were making holes in a steel down pipe because Vintage wanted to convert the well into a disposal site for water used during oil operations, Furrow said.

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About noon, the men were overcome by fumes that sent them into cardiac arrest. Johnson died at the scene and the other two were declared dead at a Ventura hospital a short time later.

Four other workers who pulled the men from the pit were sickened by the fumes but recovered after medical treatment.

Furrow said Pride investigators right away did not believe the deaths were caused by a release of deadly hydrogen sulfide gas because nobody noticed the characteristic rotten-egg odor of the vapors.