The Extech SD800 monitors air quality in schools, office buildings, greenhouses, hospitals and anywhere that high levels of carbon dioxide are generated. Selectable data sampling rate of 5, 10, 30, 60, 120, 300, 600 seconds or automatic. Maintenance free dual wavelength NDIR (non-dispersive infrared) CO2 sensor. Triple LCD simultaneously displays CO2, Temperature and Relative Humidity.