I just test drove a used car that had been previously owned by a smoker.
The smell was overwhelming. The upholstery was stained.
And this was after a thorough dealership cleaning and detailing.
There may be just enough positive pressure in a car to keep gasoline fumes out, but that doesn't work for fumes that are initiated inside the car.
Put a gasoline can inside the car and then crack a window.
Again - bottom line here - if you smoke inside a car - so does everyone else inside the car.
If you wouldn't hand your 5 year old a cigarette and let him/her smoke it - then you have no business smoking while in your car with him/her.
Unless you're willing to state that 5 year old's should be allowed to smoke, please go back to my previous post with the ostrich.