This is quickly becoming one of my best purchases to date. CO2 monitor.
I opened the box and put the batteries in and the reading was at 1600 ppm! I suspected there was a problem with airflow in my house. But now I know for sure.
In a bedroom at night with doors closed it’s almost 2,000 ppm.
Outdoor air is 400 ppm. Anything under 1,000 ppm is considered healthy indoor air, though under 800 is ideal. Cognitive function begins to decline over 1,000 and becomes pronounced over 1,600.