The phenomenon described is common to all analogue hairdryers and is not dangerous. When an electrical circuit is activated or interrupted, an overvoltage occurs between the interruption terminals - the electrodes - which triggers an electric discharge (and therefore a spark). This event is better known as an “arc flash” and is not dangerous. On a technical-structural level it is considered a positive fact: it means that the switch is functioning properly. The phenomenon, present in all professional hairdryers, is more evident in light-coloured hairdryers (white/red for example) while it is almost invisible in black-coloured hairdryers or in any case dark enough to cover the sparks.