QPM2100Duct CO2 Sensor, 0-10V / 4-20mA Output 
Duct sensor for CO2 concentrations with a CO2 measuring range over 0 to 2000 parts per million (PPM). This unit delivers a 0 to 10 Volt DC signal. Not suited for safety applications.
Maintenance-free CO2 sensing
Non Dispersive Infrared (NDIR) technology
CO2 temperature and humiditymultisensor optional
No recalibrations required
Operating voltage 24 VAC
Signal outputs 0 to 10 VDC