The CPPM-4 controls your carbon dioxide levels with part-per-million accuracy. It uses a CO2 sensor that is extremely accurate and features a ten-year life expectancy. Our combination CO2 and light level sensor is housed in a separate remote sensor enclosure that can be located up to 100 ft from the controller. The CPPM-4 can also be connected to other controllers so that the CO2 is disabled (useful when operating exhaust fans). It can be operated in fuzzy-logic mode (for compressed CO2), or on-off (for CO2 generators).