[wang_li]

If you don't have a steady flow of outside air into your car's cabin, you will soon die.

[ctdonath]

The point is there's a difference between ambient outside air leaking into the car like a sieve, vs completely sealed with air supplied via biohazard rated filtration. Also, you'd be surprised how long you can function fine in a sealed box the size of a car cab.

If you haven't seen waves of pollen wafting thru the air for miles, like we regularly see near Atlanta, you may not grasp the interest.