Air handling units, also known as ventilation and air conditioning systems, are essential systems for the mechanical ventilation of indoor spaces. Their main task is to optimize the air quality in buildings by ensuring the exchange and treatment of air. Treatment involves several important processes: First, the air is filtered to remove pollutants, dust and allergens. The air can then be heated or cooled as required to create a comfortable indoor climate. Air handling units are also able to humidify or dehumidify the air, which is particularly important in extreme climates. Thanks to these functions, air handling units not only contribute to improving comfort, but also to the health of users by creating an optimal indoor climate. In addition, they play an important role in the energy efficiency of buildings, as modern air handling systems are often equipped with heat recovery to minimize energy consumption.

Ventilation and air conditioning systems ( AHU systems) include devices for ventilating and air conditioning (heating, cooling, humidifying, dehumidifying the supply air) rooms .

Heating systems have the primary task of heating the room air in winter to create a comfortable indoor climate. They focus mainly on temperature control and are not usually designed to influence air quality or other climatic conditions. In contrast, ventilation and air conditioning systems (AHU systems) are responsible for maintaining the condition of the indoor air within certain limits in terms of purity, temperature, humidity and other factors. These systems not only provide adequate heating, but also effective ventilation and air conditioning by supplying fresh, filtered air and removing stale air. It is important to note that systems that provide direct space heating, such as radiators and convectors, are by definition not air handling units. HVAC systems, on the other hand, often integrate complex technologies such as air filtration, heat recovery and control technology to ensure an optimal indoor climate. To summarize, heating systems focus on temperature control, while air handling systems offer a more comprehensive system for regulating air quality and the indoor climate.

Free ventilation: With this method, air is conveyed by natural pressure and temperature differences that occur in and around the building. This type of ventilation uses natural conditions to let in fresh air and remove stale air. Mechanical ventilation: In this case, the air flow is actively supported by fans. These systems enable targeted control of air exchange and can operate independently of external weather conditions. Hybrid ventilation: This method combines the advantages of free and mechanical ventilation. Free ventilation is temporarily supported or replaced by mechanical ventilation to ensure optimum air quality at times of high load or unfavorable weather conditions. Within free ventilation, there are various ventilation systems that differ in the way they work. What they all have in common is that the air exchange rate is heavily dependent on the current weather conditions, the temperature conditions in the building and the outside temperature. For this reason, controlled ventilation is only possible to a limited extent with these systems. In contrast, mechanical ventilation systems allow precise control of indoor air conditions, regardless of the weather and the specific conditions in the building. These systems are particularly important in environments where constant air quality is required, such as offices, schools or medical facilities. Depending on the type of air treatment, these systems are classified as ventilation systems, partial air conditioning systems or air conditioning systems. They play a crucial role in creating a pleasant and healthy indoor climate by not only providing fresh air, but also regulating temperature and humidity.

Basically, it can be said that air conditioning systems are a special form of ventilation and air conditioning systems (AHU systems). If the outside air is only heated, these are simple ventilation systems. These systems are designed to bring fresh air indoors and regulate the temperature. However, if the air can also be cooled and humidified or dehumidified, we speak of air conditioning systems. These offer a more comprehensive approach to improving the indoor climate, as they can control not only the temperature, but also the humidity and air quality. Ventilation and air conditioning systems are therefore grouped together under the common term of ventilation and air conditioning systems, as they both fulfill essential functions to ensure a comfortable and healthy indoor climate.

VDI 6022 is a guideline issued by the Association of German Engineers that specifies hygiene requirements for ventilation and air conditioning systems and devices. It deals with the planning, manufacture, maintenance and operation of such systems in order to ensure hygienically perfect supply air quality. The aim is to protect the health of people who spend time in rooms ventilated by such systems. This series of guidelines therefore deals with the hygiene of ventilation and air conditioning systems and devices. VDI 6022 is indirectly prescribed by law via occupational health and safety: according to Section 4 of the Occupational Health and Safety Act, operators are obliged to implement the state of the art to ensure occupational health and safety in their operations. Of course, this also includes the operation of ventilation and air conditioning systems.