The Extech SD800 monitors air quality in schools, office buildings, commercial buildings, hospitals and places with high carbon dioxide levels. 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. The triple LCD display shows the CO2 concentration, temperature and relative humidity.