Maryland Occupational Safety and Health officials finished yesterday an investigation of a carbon monoxide incident that displaced 16 people from the apartments above Johansson's restaurant early Sunday morning in Westminster.
It will be a few weeks before official results of the investigation are available, but firefighters and health officials said yesterday that a propane gas heater caused the problem, which sent all 16 residents to Carroll County General Hospital about 1:30 a.m. Sunday.
Officials said residents called 911 when they began to feel ill that night. Gil Chamblin, Carroll County General spokeswoman, said the residents -- including children -- were treated and released that morning.
"We had been down there in the beginning of the week," said Jeff Alexander, chief of the Westminster Volunteer Fire Department. "In both incidents, the carbon monoxide levels were above and beyond what is considered safe."
Mr. Alexander said that in each case, the level of carbon monoxide was at or above 70 parts per million. Three residents were hospitalized in the first incident on Feb. 5.
The legal limit for carbon monoxide exposure is 50 parts per million over an eight-hour day. Recommended exposures are closer to 25 parts per million over eight hours.
"According to the law, [50 parts per million and 25 parts per million are not] supposed to have an adverse effect on the average human being," said Chris Hawley, coordinator of the Baltimore County hazardous-materials unit, which helped test the air.
"Readings that are more than 100 parts per million are potentially lethal, so we don't let residents back into their houses," Mr. Hawley said. "At more than 10 but less than 100, we advise them to leave until the problem is corrected."
The culprit in Sunday's incident was a propane gas heater placed on a low burn; earlier in the week, it had been workers renovating the basement with gas-powered tools. Each involved improper ventilation, officials said.
The heater "was burning all the oxygen in the room and producing carbon monoxide instead," said Arthur Slusark, spokesman for Baltimore Gas and Electric Co., which was called in to inspect the building's gas furnace.
By the time Baltimore County arrived to help at about 3 a.m., carbon monoxide levels had dropped to 10 parts per million because firefighters had removed the heater and aired out the building, Mr. Hawley said.
"They are lucky someone figured out that it was carbon monoxide poisoning caused by the heater," he said. "It is a big, big problem. People need to be aware that this is a potential killer."
Deputy State Fire Marshall Robert B. Thomas Jr. said yesterday that residents were able to return to their homes by Sunday afternoon, but those in four apartments may be without heat. Mr. Slusark said BGE inspectors turned off the furnace for apartments C, D, E and H Sunday when they discovered it had been installed incorrectly.
"There was no cold air return in a separate room," Mr. Slusark said, which he explained would cause byproducts of the gas combustion to come back down the chimney into the furnace room.
"This hasn't caused a problem before, but it needs to be corrected," he said, adding that the heat will remain off until the furnaces are repaired.
David Johansson, whose family owns the building, was unavailable for comment.