CRPE HEPA filters are standardized on anodized aluminum framing. The imported submicronic glass fibre media, which is water resistant and has a high tensile strength, consists of one continuous sheet folded around machine pleated aluminum separators. A fluid fire retardant adhesive when dry hardened, providing a positive seal between filter pack and rigid frame. A closed cell neoprene gasket provides positive sealing. Each filter is individually tested by the DOP penetration method for efficiency as well as for air flow and pressure drop. All HEPA filters assure a filter that is 99.97% efficient on particles of 0.3 microns in size or larger