I suggest people check out part six of Adam Curtis' Pandora's Box, that cover this.
On top of all of this we had a generation that was hammered about the dangers of a nuclear war, including the potential poisoning of the environment around a blast by fallout.
And at the core of all this we have the issue that radiation is a silent killer. We can't smell it, we can't see it, we can't feel it. This amps up the fear element greatly.
As well it should. Dangerous things that you cannot detect with any of your human senses are rightly to be feared.
This behavior is well-preserved in humans for a reason.
I said that fear was justified - not that we should or should not use those things.
Similarly we should indeed be afraid of CO for those very same reasons. I know I certainly have a healthy respect for, and fear of, CO.
If you use fire, the "invisible" risks are oxygen deprivation or monoxide poisoning. You will be quite aware that something is wrong when there is too much CO2.