It doesn't matter if it is a diesel truck in front of me, a very old car or pickup that is running rich, or a "street racer" car that has (??assuming) NOS, or the smell of raw gasoline. Is there any way of blocking that while in a car? It depends on what the smell actually is, but my symptoms can vary from pain in the sinuses, headache, nausea, or with long drives in heavy traffic: stoned. I try not to get behind a vehicle that I know will make me ill, and if I can get warning (blue smoke belching out of a tail pipe) I can turn the air to recirculated in the cabin. But that doesn't help much either. Is there anything that anyone uses that reduces or eliminates these awful and sickening odors?