A-A-1419 Filter Element, Air Conditioning (Viscous-Impingement And Dry Types, Replaceable) (Replaced By Ansi/Ashrea 52.1 And Ul900)This commercial item description covers standard dust-holding capacity, flat panel-type air-conditioning filters designed for arresting particulate matter in heating and ventilation systems in which the face valocity of the air stream approximately 300 feet per minute (fpm).