The Extech CO100 is a desktop indoor air quality CO₂ monitor that measures carbon dioxide concentrations (CO₂) from 0 to 9,999 ppm, air temperature from -5°C to 50°C (23°F to 122°F), and humidity from 0.1 to 90% RH. It comes with a user programmable visible and audible CO₂ warning alarm. The meter has a maximum/minimum CO₂ value recall function. The CO100 is complete with a maintenance free NDIR (non-dispersive infrared) CO₂ sensor and a universal AC adaptor.