Carbon Dioxide Monitor by Control Wizard Products. 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 Control Wizard Products’ 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.