My first question is: Who selected that awful tomato-red background for you site?
My real question though, is: From time to time I’ve read in the news of someone who became sick or even died due to a faulty exhaust system that fed carbon monoxide into a closed car. Because of this, I’ve long made a habit of leaving a window cracked open a bit even in bad weather.
It’s been awhile since I’ve seen one of those news stories. Does this mean that newer cars are less prone to this problem and I’m being cautious to a fault?
Overall modern cars are designed in a way that will reduce but not eliminate) the problem.
I believe you will find that modern cars allow some fresh air in even when it is cold. However that said, if you smell any exhaust when driving, don't ignore it. It can sneak up on you.It’s not necessary, and in fact depending on vagaries of airflow and which window you have open, you can actually admit exhaust into the cabin by only cracking a window. Drive with the windows up. You’ll be fine.
The CO poisoning your refer to is generally because of a leaking exhaust system. Leaks can develop in places that allow the exhaust to enter the vehicle’s passenger cabin, and even though modern cars produce much less carbon monoxide than old engines did, it’s still poisonous and can still kill you. Realize too that CO is reduced in the catalytic converter, and if the leak is foreward of the converter there’ll be more CO per volume than if it’s aft of the converter. And CO is odorless, colorless, and tasteless. You’ll just go to sleep and never wake.
The bottom line: leaky exhaust systems can be dangerous and should be repaired.
However, if the exhaust is in good shape it’s perfectly safe to roll the windows up. It’s also safe to leave one open a bit…I myself love the fresh air.