To complete a fresh air calibration on a CO2 Sensor, follow the procedure below (in both text and example menu map):

1] Ensure the Ax60+ is powered on and operating normally.
2] Press and hold Cancel+Cycle for 6 seconds to display Top-level Menu.
3] Press Cycle four times to display Calibration. Press Accept/Test to display Zero cal.
4] Press Accept/Test to show the Select sensor screen, press Cycle to select the sensor you want to
calibrate.
5] Press Accept/Test to select the sensor. The Zero level (#) screen displays.
6] Wait 1-2 minutes for the fresh air level to be measured.
7] The reading on the Zero level screen will begin to reduce. Wait for the reading to stabilise.
8] Press Accept/Test to confirm the zero calibration.
9] If zero calibration is successful, the Zero msg sent screen is displayed as per following example.
10] Press Cancel repeatably to return to the normal operation screen.