Fogging is a technique in pest control that is used for killing all the pests in closed spaces (e.g. greenhouses, homes and basements). A fine pesticide spray (aerosol) is used and directed by a blower (fogger).
Fast acting pesticides like pyrethroids are typically used, but its amount is usually very small in the liquid (water) used with the method. In some cases, e.g. a hot vapor can be used to carry the spray and keep it airborne (more effective at the same time) for longer periods.