There are two signs that the filter is full:
Indication on the display: The external control of the air filter has a display on which information such as the vacuum and the air flow rate are shown. When the filter is full, this will be reflected in the display.
Colouration of the filter: Another indication is the colouration of the filter itself. When the filter is saturated, it may have a brownish tint. This serves as a visual cue that it is time to replace the filter.
It is advisable to regularly check both the display and the filter itself to ensure that the filter is changed in a timely manner and that the air filter is maintaining its optimal performance.