iO HVAC Controls CO2-TH Co2, Temperature And Humidity MonitoriO HVAC Controls CO2 TH CO2, Temperature and Humidity Monitor The iO HVAC CO2 TH offers an intelligent way to monitor and reduce CO2 levels in an interior space by being able to introduce fresh outside air at a controlled rate. The CO2 TH requires very little user interaction. It can monitor the levels of carbon dioxide as well as humidity and temperature within the applied space and is capable of initiating alarms and corrective action if any of