Residents in eastern Montgomery County have been reporting weird odors with no identifiable source, writes Deanna Durante and Emily Rose Grassi for NBC Philadelphia.

Many people have called 911 over concerns about the safety of being exposed to these smells that ranged from burning plastic to chlorine. A Villanova professor however says it is not an emergency situation.

These smells are being sniffed out from East Norriton to Gwynedd, according to social media posts.

Dr. Stephen Strader, an associate professor of geology and the environment at Villanova University, said he experienced it as well.

“A box truck drove by and I smelled the exhaust and then it just never went away,” he said.

Strader said that he agrees with the Pennsylvania Department of Environmental Protection who said the smells are the result of an atmospheric inversion —when warm air is suppressed and pollutions like exhaust and trash linger in the air longer.

“That suppresses all that air from rising up. So, along with that heavy, dense fog anything that’s pollution or wildfires or just burning or anything that normally would get mixed into the atmosphere is kind of held down. Almost like the lid on a soda bottle,” he explained.

Once weather patterns change, the air quality will improve.

Read more about what residents have been saying about the strange smells at NBC Philadelphia.