Permanent, self-charging electrostatic air filter. High efficiency in removing airborne particles. Self-charging as a result of air flow through the media (no expensive, troublesome power supply required). Permanent effects lasting the life of the filter. Attraction of all particles due to the presence of both plus and minus charge. Safety - No electrical hazard or performance loss due to power outage. Withstands temperature to 212 °F (100 °C) and is unaffected by humidity. TYPE CR Layers of woven polyethylene fabric collect airborne particles including pollen. Non-woven collector pad captures and retains a large amount of these particles. Reinforced by galvanized steel harware cloth. Enclosed in a rigid, rust resistant galvanized steel frame for easy servicing. Ideally suited for commercial and residential furnaces and air conditioners. TYPE HD Heavy duty industrial application features a unique 3-in-1 filter construction. Aluminum mesh intake screen prevents insects, lint and other large particles from entering the interior of the filter. Shredded polyethylene arrests troublesome fines (subvisible particles) and holds them throughout the depth of the media. A spray bonded, non-woven collector pad stops and holds airborne particles. Reinforced by galvanized steel hardware cloth. Enclosed in a rigid, rust resistant galvanized steel frame for easy servicing.