Rigid Box The Aero-cell is a rigid air filter engineered to provide medium and high efficiency filtration combined with a prolonged life cycle. Each Purolator Aero-cell filter utilizes a high-density filter media composed of ultra-fine glass fibers laminated to reinforced, high-strength nylon backing. The media is continuously bonded to expanded, corrosion-resistant, electro-galvanized steel which allows a 95% open face area. The Aero-cell is capable of withstanding 7" w.g. in Variable Air Volume (VAV) applications, the Aero-cell maintains consistent filtering performance throughout a full range of velocities. The filter media shall have an average efficiency of 65% when tested in accordance with ASHRAE Test Standard 52.1.