Friction from fine dust (e.g. drilling dust, sand, plaster dust or flour) inside the suction tube and hose causes static charge to build up in the appliance.
To avoid the unpleasant effects of these electrostatic discharges, a metal inlay has been incorporated into the underside of the handle on most Miele vacuum cleaners. Please make sure that you keep your hand in constant contact with this metal strip during vacuuming.