The GasCheck is a series of low cost CO2 sensors that offer high accuracy, good long term stability, negligible cross sensitivity, small size and low power requirement. The basic GasCheck is available in three ranges 3000ppm, 3% and 10% with a 0 to 1 V non-linear output. A linearization board can be added as an option to give linear 4 to 20 mA output. The option of a diffusion assembly is available for the 3000ppm unit.