The primary filter is suitable for the primary filtration of air conditioning system, mainly used to filter dust particles over 5m. There are three types of primary filters: plate type, folding type and bag type. The outer frame materials are paper frame, aluminum frame and galvanized iron frame. The filter materials are non-woven fabric, nylon net, activated carbon filter material and metal mesh. The protective net has double-sided plastic-sprayed barbed wire and double-sided galvanized barbed wire. Characteristics of primary filter: low price, light weight, good versatility and compact structure. Mainly used for: central air conditioning and centralized ventilation system pre-filtration, large air compressor pre-filtration, clean return air system, local high-efficiency filter pre-filtration, stainless steel frame for high-temperature resistant air filter, high-temperature resistant 250-300℃ filtration efficiency. This kind of efficient filter is commonly used in the primary filtration of an air conditioning and ventilation system, and is also suitable for simple air conditioning and ventilation systems that only need primary filtration.