This CO2 sensor not only measures the gas concentration, also due to the implementation of a PID algorithm can give a signal proportional to control the airflow of a fan, damper or an HRV.

This sensor combines the functions of a sensor and a controller at the same time being able to maintain optimal air quality through the jumper configuration of the indoor air quality reference or setpoint with the desired concentration in the room. This allowed maintaining air quality depending on the occupancy of the room and thus saving energy to be able to regulate the speed of a fan or an opening damper. 
 

Press_CO2PID82

Datasheet