Koolau
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
IMO it's reasonable to be concerned about other contaminants in homes and other settings and CO2 is a relatively easy but imperfect way to measure indoor air quality.
Yeah, CO2 would give an indication of how tightly the home is sealed. CO2 will naturally build up in an enclosed space. The CO2 itself will not be an issue but might suggest other contaminants are also being concentrated. Of course, if there are no other actual contaminants to concentrate, it shouldn't matter.
You could look at it as a "good" thing if CO2 levels are higher inside than outside. It means all your efforts to plug leaks and seal windows and doors, etc., are w*rking. I'd never open my windows in the middle of winter because my CO2 levels were at 2000 or 3000ppm. I'd be celebrating how all my weather sealing and insulation was w*rking.
As mentioned earlier, the physiological effects of a few thousand ppm of CO2 should be minimal or non-existent.
If anyone has data that suggests otherwise, I'd like to see it.