How often should I wash the filter, and how do I dry it properly?

You should wash your filter at least once a month to maintain optimum suction power. Wash it with warm, running tap water, gently rubbing with your fingers to remove dirt, then shake out excess water. Leave your filter to dry for at least 24 hours in a well-ventilated, warm place — do not dry it in a tumble dryer, microwave, or near a naked flame. (Page 9)

From the official Dyson V10 Cordless Stick Vacuum manual, page 9

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