Temperature inversion blamed for foul odor reported in Delaware County

Officials in Delaware County said a phenomenon called "temperature inversion" was to blame for creating a foul odor that many residents reported smelling this week.

Pennsylvania Department of Environmental Protection Regional Communications Manager Stephanie Berardi said the temperature inversion was confirmed by the after an inspection team was sent to Delaware County Tuesday.

The National Weather Service defines temperature inversion as "a layer in the atmosphere in which air temperature increases with height. 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," the National Weather Service glossary reads.

Delaware County's Office of Emergency Management began receiving calls about an unknown odor Monday morning. Some believed the smell was from a nearby fire, while others likened the odor to bug spray. 

Delaware County Emergency Services Director Tim Boyce said his office received calls all day, and officials had a tough time immediately pinpointing the source. The smell began to dissipate by Tuesday, and no new reports have been made.