How often should the CO2 sensor be calibrated?

We recommend checking that the sensor is still properly calibrated every 6 to 9 months.

This is accomplished by simply placing the sensor outside on a day when the outside temperature is above 10C (50F) and when there is not too much wind. If after 10 minutes the sensor displays a value between 400 and 450ppm you can consider that it's still properly calibrated.

If the sensor is outside that range, calibration is recommended.