Titan Controls Portable Carbon Dioxide (CO2) Temperature & Humidity Monitor, Handheld - Atlas 5 Measures Carbon Dioxide (CO2), Temperature and Humidity CO2 Range: 0 Parts Per Million (PPM) to 9,999 PPM Temperature Range: 14F to 140F Humidity Range: 0.1% to 99.0% Runs off 4 AA batteries (included)