ETNA AKI683 Série Mode D'emploi page 65

MAINTENANCE
Odour filter (recirculation use)
In the display of the extraction unit, 'F' and 'C' will be shown alternately after 120 (downdraft)
operating hours. The odour filter needs maintenance.
Depending on which filter is applied to your system, filter maintenance should be performed.
Please refer to the manual of the filter that has been installed.
After the maintenance, reset the memory of the filter saturation indication.
EN 31