Abstract: The one-way valve is preferably formed of lightweight material such as plastic and includes a highly flexible rubber or plastic membrane which seals against a sealing edge to prevent the back flow of air therethrough but may be readily lifted off the edge by air flowing in the desired direction. A number of protuberances prevent seating of the membrane against the exhaust openings and the valve face and a spider member supports the valve within the valve housing. An enlarged flange extends about the valve which may be sealed by suitable means such as adhesive or heat to the protective clothing in which the valve is intended to be installed. The protective clothing is formed of impermeable material, preferably polyethylene plastic. An air supply hose is attachable to the clothing to supply air to the interior of the protective clothing from an outside air source.