The dust container is full.
Activating the ComfortClean self-cleaning function
Always run the interim cleaning function for the fine dust filter before emptying the dust container. You should also run it whenever the suction power begins to drop. This enables the vacuum cleaner to achieve the very best cleaning performance again straight away.

Turn the screw cap 3 times by 180°.
When turning the cap, you will hear a noise, which is a normal part of how the ComfortClean self-cleaning function works.
Emptying the dust container
Empty the dust container at the latest when the dust has reached the Max. marking on the dust container.
Hold the dust container close to the bin to prevent dust from billowing out.

Press the release button on the bottom of the dust container.
The flap will open and the dust will fall out.
Close the dust container flap, making sure it clicks into place.