Last year we started to notice a strange, almost chemical type smell, when the heater ran. I changed the cabin filter and cleaned some debris out from under the exterior cowl section.( leaves , twigs, road dirt, rotted vegetation). Thought it helped for a bit but summer came and forgot about it, This year worse than ever. Wife is asthmatic and it bothers her big time. She drives car with window cracked and mouth covered.

Otherwise car pretty reliable. I've replaced the lower control arms since we've had the car. Very economical vehicle, great in snow but rides rough because it is so light. Had a problem with the sun roof leaking until I found out it was the drains blocked. I can't figure out this smell issue. Any suggestions would be appreciated. Surely I'm not the only one with this issue.