Techno Line WL 1020 Manuel D'utilisation page 32

Calibration of TVOC and CO2:
The sensor has an automatic factory calibration and can
therefore be used immediately. This usage variant is
recommended. A manual calibration is also possible.
Manual calibration:

When using adapter, press and hold the "+" button for 3
seconds and then press the "SET" button to confirm the
calibration operation ("CAL" and time display alternately).

The sensor will be calibrated after 2 hours. Please start the
calibration in a non-polluting and ventilated environment.
(Please open your window for ventilation while calibrating)

Calibration will be terminated if the DC power supply is
disconnected during calibration process.

It is recommended to repeat the manual calibration every 1
to 2 weeks.
EN12