'Foul' Odors In Delaware County Caused By 'Atmospheric Inversion'

DELAWARE COUNTY, PA — A unique atmospheric phenomena is to blame for bizarre smells lingering in the air around Delaware County in recent days, environmental experts have confirmed.

The "thermal inversion," first reported by NBC Philadelphia and confirmed by the U.S. Department of Environmental Protection, has caused residents in many parts of the county to take to social media with confusion and concern.

Reports of exactly what the smell was varied from person to person and place to place. Some described the smell of trash, others described a burning or a fuel odor, others smelled exhaust.

They were all right.

A thermal inversion causes air molecules and smells to be trapped close to the ground, so that when a bad smell wafts by, it doesn't dissipate in the way it normally would.

"A temperature inversion is a layer in the atmosphere in which air temperature increases with height," the National Weather Service explains. "An inversion is present in the lower part of a cap. The cap is a layer of relatively warm air aloft (above the inversion). Air parcels rising into this layer become cooler than the surrounding environment, which inhibits their ability to ascend."

In extreme cases, thermal inversions trap smog and other particulates close to the ground for extended periods of time and cause significant health hazards.

However, a shift in the weather in the coming days will end the inversion in Montgomery County, experts say.