Titan Controls® Atlas® 5 is a portable monitor that measures Carbon Dioxide (CO2), Temperature and Humidity. CO2 Range: 0 Parts Per Million (PPM) to 9,999 PPM. Temperature Range: 14°F to 140°F. Humidity Range: 0.1% to 99.0%. Backlit LCD display function and auto shut-off feature. Runs off 4 AA batteries (included).