We are just concerned that if you are stuck in traffic for any significant period of time, the carbon monoxide might build up.
If you don't mind headaches and blue lips, then keep on truckin !

Reminds me of the time when I was assigned a company car that had an exhaust leak at the muffler.
I had headaches for days, and the boss wouldn't pay to have it fixed cause it wasn't making any noise.
I talked him into riding around with me for a day, the next day it was in the shop to get fixed.