Abstract: A sealing device for protecting individuals within a building or home against harmful biological and chemical agents outside the building or home comprising a plastic sheet, pre-sized to fit, for example, over a standard-dimension window and having an adhesive strip, the adhesive strip being attached along an outer peripheral edge portion of the plastic sheet for securing the plastic sheet over the window and a method of separating at least one sealing device from a supply roll of identical sealing devices, peeling off a removable backing strip from the adhesive strip in order to expose a tacky surface of the adhesive strip, and systematically adhering the tacky surface of the adhesive strip along a window opening so as to secure the sealing device over the window or window area.