An electrically-powered device designed to filter air [usually through a high-efficiency particulate air (HEPA) filter] in surgical theatres by producing a directed, non-turbulent flow of clean air to provide an area free of contaminants and reduce the risk of patient infection. It may be mobile (on wheels) or fixed [e.g., to the ceiling], and provides a curtain of fast moving air that helps to delineate the sterile field; some types allow connection of a hose with a nozzle designed to be adhered to the patient to direct the filtered air across the surgical site. An operating light or light system may be mounted to this unit.