Abstract: A device in the form of a cap, for generating an isolation barrier for airborne pathogens between the wearer's face and the environment. A major part of the outer surface comprises filter material, allowing filtered air to flow from the environment into a chamber beneath the surface layer. A fan sucks air through the filter element and into the chamber. A horizontally oriented slot is situated across the visor portion of the cap structure, in front of the forehead of the person when the device is worn by the person. The slot has a width substantially smaller than the length. The flow of filtered air within the chamber is directed out of the slot as a curtain-like flow of filtered air in front of the face of the person. A cross-flow fan mounted just above the slot is most effective in generating the curtain flow.