The Extech CO100 is a desktop indoor air quality CO2 monitor that monitors 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 includes an audible and visible CO2 warning alert that can be programmed by the user. The meter includes a maximum/minimum CO2 value recall function. The CO100 comes equipped with a maintenance-free NDIR (non-dispersive infrared) CO2 sensor and a universal AC adaptor.