This is a non-dispersive infrared (NDIR) measurement technique that measures CO2 concentration through infrared spectroscopy. This optical technology may exhibit measurement drift over time, which it automatically compensates by the OPEN’R product. This method is effective and reliable in an environment where the CO2 level reaches at least a minimum of 400 ppm for several consecutive hours: at night and on weekends for communal spaces, during the day in a room.