Vacuum cleaner for use in industry and household comprising a housing and an electric motor driving the blower generating the working vacuum, and optional maneuvering means for moving a suction nozzle over the material to be cleaned. There is provided in the area of the channel passed by the dust and dirt particles drawn in, an optical sensor comprising a light transmitter and a coacting light receiver so that the quantity of the dust and dirt particles drawn in at any time is detected. After comparison of the value so determined with a given threshold value, either a visual and/or an acoustic signal are obtained and/or a power variation of the electric motor driving the blower is effected.