The different types of air according to DIN EN 12792

In building services engineering, distinguishing between different types of air is of central importance, as it contributes significantly to ensuring an optimal indoor climate. Depending on the location and specific requirements, different types of air are defined in the relevant standards. For residential buildings, this is DIN EN 12792, while DIN EN 13779 applies to non-residential buildings. Both standards describe in detail the different types of air and how they differ in terms of their function and area of application.

Technical systems for controlled home ventilation ensure continuous air exchange, thereby guaranteeing a healthy and pleasant indoor climate. The targeted control of the various types of air is essential here, as each type of air performs a specific task – from the intake of fresh outside air to the targeted supply to the rooms and the removal of stale air.

Only through the correct application and combination of these types of air can efficient and hygienic ventilation be ensured, promoting both the comfort and health of the occupants.

 

An overview of the most important types of air:

Outside air

The abbreviation ODA (outdoor air) refers to air that enters ventilation systems through intake vents. Its quality depends primarily on the location of the building. To prevent dust from outside entering the interior, it is filtered after being drawn in. Special pollen filters are available as an option for allergy sufferers.

Supply air

Depending on weather conditions, the clean air that is drawn in is heated, cooled, humidified, or dehumidified and fed into the individual rooms of the building. This is referred to as supply air or SUP supply air. In DIN EN 12792, it is colored green, red, blue, or violet depending on the treatment, and in DIN EN 167982-3, it is colored blue. Supply air can be obtained not only from outside air, but also from secondary air and mixed air.

Our Supply air elements:

       

Recirculating air

Recirculated air refers to used air that is fed into a room from other rooms. Before this, it is treated using various methods. As it is reused air, recirculated air can contribute to the spread of pathogens, odors, and other undesirable substances. For this reason, the process is now rarely used in residential and work areas. However, recirculated air is very important in industry. Here, it is mainly used in areas where harmful substances must not escape to the outside.

Secondary air

Secondary air is similar to recirculated air. The only difference is that it is fed back into the same room from which it was previously extracted. Several treatment steps may also be involved here, such as cooling. Secondary air is often used in recirculating hoods in kitchens, for example. This allows particles to be filtered out of the air before it is returned to the room.

Mixed air

When outside air mixes with recirculated air from the building in the ventilation system, this is referred to as mixed air, which can be supplied to the room as supply air. Mixed air can reuse the moisture and heat from the exhaust air. At the same time, the room is supplied with fresh air from outside. Since this process has hygienic disadvantages, as does the use of recirculated air, it is rarely used today.

Exhaust air

The stale air extracted from the room is referred to as exhaust air. In living spaces, it usually contains high levels of moisture and carbon dioxide. Odors and other contaminants are often present as well. The heat contained in the exhaust air is often recovered via a heat exchanger and then transferred to the fresh supply air.

Our exhaust air fans:

       

Outgoing air

Outgoing air is the air that is discharged from the ventilation system into the open air. It is usually discharged through openings in the outer wall or on the roof of the building. Even if it has previously passed through a heat exchanger, it usually still contains a lot of heat.

Leakage air

Leakage air is air that escapes from the ventilation system in an undesirable manner. In practice, it is impossible to completely prevent air loss. A system always has a certain level of tightness and is assigned a tightness class accordingly. Leaks can also occur due to faulty installation or damage to the ventilation system. These are often accompanied by a high loss of heat and sometimes also by the escape of harmful substances. Therefore, air leakage should be reduced as much as possible.

Infiltration air

The term infiltration refers to the entry of air into a building through leaks. These can be located in the building envelope or windows, for example. This is a natural form of ventilation. In the past, it was an essential factor for air exchange in buildings. Today, building envelopes are increasingly airtight and offer little opportunity for natural air exchange. For new buildings and major renovations, a ventilation concept in accordance with DIN 1946-6 is now required to ensure sufficient air exchange.

Exfiltration air

Exfiltration is the opposite of infiltration. Exfiltration refers to air escaping from a building through leaks. It is also part of natural ventilation. Due to the increasing airtightness of buildings, exfiltration also occurs only to a limited extent in newer buildings. However, natural ventilation continues to be used specifically in certain buildings, such as stables or industrial buildings.