Air Conditioner problems of the 2019 Subaru Ascent

When the car idles for even short periods of time (5 minutes) the inside of the car will start to smell like fumes (exhaust type smell). This happens in any environment (parking lot, our driveway, rural area) when the car is in park and still running. Rarely have I smelled the fumes upon starting the car, although it has happened before. The problem has occurred in every season and with the car blowing out warm, neutral, and air conditioned air. This was noticed very shortly after purchasing the car in September of 2018. I have taken the car in to the Subaru dealership three times and they haven't been able to find the issue. The first time they were able to detect the smell but found no problem to correct. The other two times they said they weren't able to replicate the smell even after leaving it on for an hour. I can elicit the smell every time if I let it run for a few minutes while parked. Others appear to be having this issue as well and are being told the same thing by their dealerships. I am very concerned about this issue as my children may be affected when they are in the car.