Air Handling Unit (AHU): Air Handling Unit (AHU) is a centralized air handling system that originated from a forced hot air heating and ventilation system where equipment is centrally located and heated air is distributed through ducts. The basic centralized system is an all air single zone system, which generally includes components such as fans, heaters, coolers, and filters. The AHU referred to here refers to a primary return air system, whose basic working process is to mix fresh air from outside the room with a portion of the indoor return air, and filter out harmful substances such as dust, smoke, black smoke, and organic particles in the air through a filter. Clean air is sent through a fan to a cooler or heater for cooling or heating, to a comfortable and suitable level, and then sent into the room. The air conditioning process varies depending on the winter and summer seasons, and the typical centralized air handling system also has different conditioning processes. Equipment used to regulate indoor air temperature, humidity, and cleanliness. There are air heaters, air coolers, air humidifiers that meet the requirements of heat and humidity treatment, air filters for purifying air, mixing boxes for regulating fresh air and return air, and mufflers for reducing fan noise. All air handling units are equipped with ventilation fans. According to the annual air conditioning requirements, the unit can be equipped with an automatic regulation system connected to cold and heat sources. The fresh air unit mainly deals with the state points of outdoor fresh air, while the air handling unit mainly deals with the state of indoor circulating air. Compared with fan coil units with fresh air systems and unit air conditioners, it has the advantages of large air volume, high air quality, and energy saving, especially suitable for large space and high-volume systems such as shopping malls, exhibition halls, airports, etc. A good air handling unit should have the characteristics of less space occupation, multiple functions, low noise, low energy consumption, beautiful appearance, and convenient installation and maintenance. However, due to its multiple functional sections and complex structure, in order to achieve a comprehensive consideration, designers and construction units are required to compare materials, manufacturing processes, structural characteristics, and selection calculations from multiple perspectives in order to achieve satisfactory results.