Open the device by following these steps:

Place the device on a non-slip surface with the top facing downwards

Remove the filter cassette from the top part of the housing.

Undo and remove the 6 screws (34).

Open the bottom of the housing (35) away to the side.

Undo the connecting cables for the humidifier (42) and the alarm (43).

Make sure the power supply plug is disconnected.