HEPA filter unit box is an ideal terminal filter device for the 1000-, 10,000-, and 100,000-class air-conditioning systems. It can be widely used in the purification of air-conditioning systems in the pharmaceutical, health, electronics, and chemical industries. The high-efficiency air supply port is used as a terminal filtering device for retrofitting and newly-built clean rooms of 1000-300,000 levels, and is a key device to meet the purification requirements. It includes a static pressure box, a diffuser plate, a high-efficiency filter, and the interface with the air duct can be a top or a side connection.