CO2 Controller (Stand alone) Solatel CO2 Controller (Stand alone) (SOLCO2-300)Simply set the desired CO2 level and the CO2-400 controller does the rest. The Sensor Unit has a display and 3 buttons (SET, +, and -). By default, the controller displays actual room CO2 PPM (Parts Per Million). Using the buttons, you can display and change the set point (also in PPM). The sensor unit is connected to the control uni... — Ships from HF: OR, CA, CO, MI, PA USA....more info.