There is a easily gross smell in our motorcar for some reason

Lately, I have been noticing that there is a easily gross smell in our car.

I only notice it whenever I turn on the furnace, though.

This would be a plus if it were in the middle of the summer, but since it’s the middle of the Winter time & the hot & cold temperatures around here are chilly cold, I am consistently turning on the furnace. As a matter of fact, every single time I get into the car, the first thing I do is turn the heating program on full blast. The hot & cold temperatures where we live have been in the 20s & the teens for the past week, & it doesn’t seem savor it’s gonna start heating up around here anytime soon. According to the weatherman on our local up-to-date station, this has been 1 of the coldest winters on record for years. Anyway, I can’t exactly go without our heating program in our motorcar until the weather starts heating up. It’s just too chilly for that right now. I did some research online about what could be causing the smell issue in the car, even though I can’t easily find much of anything. My problem now is that I don’t recognize whether I should take the motorcar to a mechanic for them to check out the furnace, or to an Heating & Air Conditioning specialist. It seems as if either 1 of these professionals would be able to service the heating problem, even though I don’t recognize which 1 would be better. I believe it doesn’t easily matter, as long as I get the heating fixed!

commercial air conditioning system