Yes, but I mostly did it like some others around the start of the pandemic due to all the time everyone was spending indoors and I wound up getting a few device

Yes, but I mostly did it like some others around the start of the pandemic due to all the time everyone was spending indoors and I wound up getting a few devices from Awair. After doing this for a couple of years now, at least in my home, CO2 really never rises to the level that it's a concern. This is largely because my HVAC system is configured to circulate the air in my home every 30 minutes regardless of heating or cooling. With this feature off, yes, CO2 does eventually build up to unhealthy levels rather easily in rooms that have doors closed and related. Ultimately, this experiment gave me a greater appreciation for my HVAC system. On a side note, monitoring rising CO2 levels can, well, be used as a detection method to determine whether someone is in a room and for how long they've been there.