You need to wash it at least once a month with warm water and let it dry completely for 24 hours. Using it damp will damage the machine.
- Twist the filter anti-clockwise and pull it away from the back of the machine.
- Tap it gently over a bin to remove loose dust.
- Wash it under warm, running tap water. Gently rub the filter with your fingers.
- For a deeper clean, place your hand over one end, fill the filter with warm water, cover the open end, and shake firmly.
- Shake out all excess water. Shake with the filter in both upward and downward positions until no water comes out.
- Dry the filter for at least 24 hours in a warm, well-ventilated place. Place it with the pleated filter end facing upwards.
If that didn't work: Make absolutely sure the filter is bone dry before refitting. Do not use a tumble dryer, microwave, or near a naked flame. A damp filter will damage the motor.
Heads up: Never use detergents, polishes, or air fresheners on the filter. Just warm water.