US Patent 8146594 Flat-folded personal respiratory protection devices

A personal respiratory protection device that includes a multi-layered structure and first and second means for attaching a headband. The multilayered structure includes a filter medium and is divided into a flat upper panel, a flat non-rectangular central panel, and a lower panel. The central panel is separated from each of the upper and lower panels by first and second lines of demarcation. The first and second lines of demarcation converge towards the first and second means for attaching a headband. The multi-layered structure can be folded at the respective lines of demarcation so that the device can be folded flat for storage and can be opened to form a cup-shaped off the face air chamber over the nose and mouth of the wearer while an upper peripheral edge and a lower peripheral edge contact the wearer's face when the device is in use.