Product review (5 stars): CO2 meter
We have a very tightly constructed home and this unit allows us to monitor CO2 levels in the home. We just installed a replacement HRV (hear recovery ventilation system) in the home and started monitoring the CO2 levels. It is surprising how quickly CO2 builds when the house is closed up and there are more than a couple people in the home. Good thing this has a reset button because the alarm can get a bit obnoxious until the HRV gets more fresh air into the house.