2015 Jeep Cherokee - Fumes

jeep

#1

After returning from a car trip, began to get fumes into the interior. Seems like it’s after the engine warms up and comes thru the vents. One place I took it thought there was a dead animal (they couldn’t find it). The other place did a cursory look but couldn’t identify the source, maybe an oil drip. How do I track down the problem? It’s becoming a health issue because of getting ‘gassed’.