Not trying to be rude, but yes carbon dioxide, not carbon monoxide, and
where can I buy a sensor?

As a veteran confined to my home, I have time to think and act only in my
small corner of the world. Since I am in my home almost 24 hours a day, 7
days a week, I would like to maximize the health I have. I exercise and get
fresh air outside my back door, but as it gets cold, I spend much more time
inside. So the subject line is my question and how do I monitor it.

I ask because this month when the furnace 1st kicked on I had to have a
repair person deal with a carbon monoxide issue, so now I have 3 carbon
monoxide detectors, 1 in the furnace roon, 1 in my bedroom and one in the
main room of the house.

Thanks in Advance!
Andy