This compact device is a triumph in the field of economical digital CO2 monitors. Using a patented, dual-beam infrared sensing system, this unit displays carbon dioxide levels from 0 - 10,000ppm (accuracy of +/- 50ppm or 5%, whichever is greater), temperature from 32-122° F, 0-50° C (accuracy of +/- 2° F, 1° C). This unit can also be used to spot-check ventilation rates. Requires four "AA" batteries, or the included AC adapter. (Please note: this unit is for spot checking CO2 and temperature levels; it is not designed to be permanently installed in a high-humidity area. Long-term placement in a high-humidity environment may render the unit inoperable.)