https://www.co2meter.com/products/personal-co2-monitor?variant=1604764762132 https://www.co2meter.com/products/personal-co2-monitor?varia... this one, it's 400

https://www.co2meter.com/products/personal-co2-monitor?variant=1604764762132 https://www.co2meter.com/products/personal-co2-monitor?varia... this one, it's 400$ and totally worth it. I've probably made up easily $400 in productivity in a month.