Carbon Dioxide Monitor by Control Wizard. 0-5000 PPM Range. 20 volt AC transformer. LCD display. Infrared sensor is very accurate. Adjustable silent flashing alarm. May be used in conjunction with the Control Wizard CO2 Controller to automatically turn CO2 systems ON and OFF a pre-set level. Turns CO2 ON at 150 ppm below set-point and OFF at 150 PPM above set-point. Truly a great value for the customer.