Weather inversion triggers carbon monoxide alarms in Pittsburgh

| Thursday, Oct. 25, 2012, 9:02 a.m.

A rare weather inversion that set off several carbon monoxide alarms kept Pittsburgh paramedics busy Thursday morning, a city EMS official said.

The alarms began about 2:30 a.m. in Squirrel Hill and continued until just before 11 a.m., EMS Division Chief Bob Farrow said. Medics investigated 11 alarms in East End neighborhoods. No one was sickened, he said.

“I can't say all of them are inversion calls, but most likely the majority of them are,” Farrow said. “Normally, there's one or two a day, not 10.”

First responders became suspicious when four calls came between 7 a.m. and 8 a.m., and dispatchers contacted the National Weather Service.

“That's very, very unusual,” Farrow said. “Then you think there's something environmentally going on. The last one was about two years ago in the East End.”

An inversion occurs when a layer of warm air above Earth's surface traps contaminants beneath it, said meteorologist Lee Hendricks of the National Weather Center in Moon. About 500 feet up, the air is about 7 degrees warmer than it is at ground level, Hendricks said. The inversion breaks up when the air at the surface warms sufficiently.

Margaret Harding is a staff writer for Trib Total Media. She can be reached at 412-380-8519 or

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