An AHU, or air handling unit, is a piece of equipment used in HVAC systems to regulate and circulate air throughout a space. It is a large metal box that conditions the air, which helps in creating a perfect atmosphere. The AHU collects outside air and room air, removes dust and other particles from the collected air, adjusts the temperature and humidity, and then supplies comfortable and refreshing air-conditioned air into the rooms through ducts. The AHU is usually installed on the roof of buildings and, through ducts, the air is circulated to reach each of the rooms in the building in question. The ultimate aim of an air handling unit is energy efficiency, and this is mandatory since 2016 by the European Ecodesign Regulation 1235/2014. An AHU can also be used to ventilate places where air conditioning is provided by radiators or underfloor heating, for example. The AHU performs other functions, such as purifying, air-conditioning, or renewing the indoor air in a building or premises. The places for which the AHU is intended are those in which the flow of people is very large and accumulates many people at the same time and whose natural ventilation is limited, such as hotel dining rooms, function rooms, restaurants, convention halls, laboratories, clean rooms, or operating theatres, among others.