the present invention is directed to methods and apparatus for cleaning industrial and commercial operations hard surfaces , e . g ., concrete and asphalt slabs , walls , tanks , grates , and ship hulls , contaminated by oil and chemical spills or barnacles . the methods and apparatus of the present invention produce a high velocity airflow about only the periphery of the area being cleaned by the device to provide improved entrainment and removal of cleaning fluid and dislodged debris . high velocity streams of cleaning fluid are directed against the surface from nozzles disposed on rotating arms of a hub suspended within the portable housing of the slab cleaner . the spent cleaning fluid and dislodged debris are removed by the application of a vacuum to a chamber extending about the periphery of the housing to create the high velocity airflow . thus , high velocity airflow is developed without fear that the slab cleaner will be sucked down and become temporarily stuck on the surface being cleaned . control of the airflow through the central housing also may be achieved through adjustment of an air vent therein , together with the action of a flexible skirt or seal about the exterior of the peripheral chamber .