Hydrogen sulfide lethal in confined spaces

Chemical has killed 47 workers in United States

Pittsburgh Post-Gazette

It was an unexpected burst of hydrogen sulfide gas from a pipe, authorities say, that claimed the lives of two workers and injured four others during routine night shift maintenance at the Bruce Mansfield coal-fired power plant.

As details emerged on Wednesday from the overnight accident in Beaver County, the deaths serve as a reminder of the perils of the Pittsburgh region’s work sites.

Hydrogen sulfide — a potent gas that lingers around sewers, wastewater treatment plants, oil and gas water tanks and wells — is found where organic material decomposes, said Wayne Vanderhoof, a workplace safety expert and president of RJR Safety Inc., based in Claysville, Washington County.

The colorless gas, which has a sulfurous “rotten egg” smell at low concentrations, can be lethal when inhaled in confined, underground spaces where workers could encounter stagnant pools of water or waste material, he said.

“It will get into your system and, above 100 parts per million, that’s essentially your body just can’t process it,” said Mr. Vanderhoof, who leads workshops for the region’s employers on how to prevent hydrogen sulfide deaths.

“It takes the place of the oxygen you’re breathing in,” he said. “It incapacitates you, so you cannot rescue yourself or get out of your situation.”

The Occupational Safety and Health Administration said on Wednesday it has opened an investigation into the incident. No finding of fault has been released.

At power plants, employees can encounter hydrogen sulfide when working near the wastewater treatment systems that clean or recycle the facility’s waste product, which can contain a slowmoving mixture of hazardous pollutants. “The sludge was likely a liquid to a muddy consistency,” Mr. Vanderhoof said.

In situations when workers have to repair piping, he advises them on the proper technique: Turn a valve to shut the flow of sludge and chain the valve to prevent any other employee from accidentally turning it back on. Carry an air monitor that can detect any abnormal gases.

While 100 parts per million of hydrogen sulfide can become fatal, he recommends workers wear a respirator that delivers a clean source of oxygen when concentrations reach just 10 parts per million.

The Bruce Mansfield workers had descended into a “confined, well-type” space and removed a piece of a pipe, according to a report from Pennsylvania State Police on Wednesday. Hydrogen sulfide gas was released.

The two fatalities are remarkable for the Pittsburgh region, which has not been a hydrogen sulfide death on the job in recent memory, Mr. Vanderhoof said.

Nationally, 47 workers have died from hydrogen sulfide inhalation on the job, according to fatality statistics collected by the U.S. Bureau of Labor Statistics. Most of the deaths have occurred on work sites in manufacturing, oil and gas, mining and construction.

OSHA reported 25 workplace deaths in the region in 2015, a sharp uptick from 18 in 2014, but lower than the annual average of 36 reported from 2008 to 2013.