Don’t assume when someone brings up a health hyperoptimization they’re stressing out about it.
In fact, lots of people who do these sorts of things actually enjoy what amounts to a health hobby, in the same way any other hobbyist likes to geek out about their respective hobby.
Stressing out about minutiae of your own health is, in most cases, wasted effort.
However, putting that effort into fixing those small things for millions of people usually is worth it. For example, could OP contact their local building standards department and push for CO2 monitors in all new buildings? Could they do a study and publish the results to give a better scientific backing for any changes? Could they publish designs for a combined smoke and CO2 alarm?
If they are truly powerless to do anything like that, then they should just ignore the whole thing and worry about more day to day risks, like slipping on ice on their front yard.
In fact, lots of people who do these sorts of things actually enjoy what amounts to a health hobby, in the same way any other hobbyist likes to geek out about their respective hobby.