vacuum cleaner, mechanical device using a draft of air to remove dust, loose dirt, or other particulate matter from dry surfaces. It is especially useful on highly textured surfaces, such as carpets and upholstery, that are difficult to clean by wiping or brushing. Usually, an electrically powered fan is used to produce a zone in which the air pressure is below atmospheric pressure, causing a draft of air to flow through the material to be cleaned, carrying the small particles with it. The draft passes through a filter bag which traps the particles, and the flow of air is then discharged back into the atmosphere. In some machines the electric motor and wiring are sealed so that wet surfaces can be cleaned safely.