Condair HumiLife

Dry Indoor Air:
When and How to Humidify?

Air humidification for controlled domestic ventilation

Dry Indoor Air: When and How to Humidify?


Dry air during the heating period
An essential difference between warm and cold air is the amount of water contained in the air. Warm air can absorb much more water, which is why the air is usually humid enough in summer and is perceived as pleasantly comfortable. Cold air, on the other hand, can only absorb a small amount of moisture and accordingly becomes dry when heated.

The relative humidity (RH) is the most conclusive indicator of the current humidity status of the air. This value indicates, as a percentage, how far the humidity is from maximum saturation (100%). A value in the range of 40–60% is considered optimal for human health as well as for hygroscopic materials (paper, wood, etc.). In winter, cold dry air enters our homes through ventilation. Once inside, it is heated up. The value of relative humidity thus drops rapidly and the air, which is already dry, becomes even drier.

Compelled to saturate itself
The distribution of humidity in a room can best be compared with the distribution of temperature. If the temperature drops at one point in the room, for example if a window is opened in winter, the temperature drop is distributed evenly throughout the room within a very short time. Not only does cold set in right beside the open window, but the air becomes cooler across the whole room.

Just as the temperature does, the air humidity equalises all the time, too. If the air is too dry, it begins to draw moisture from furniture, parquet or even the human body. The air dries out its surroundings, so to speak, in order to saturate itself with moisture.

Health effects of excessively dry air
For people, dry air is not just unpleasant, it can even be dangerous. This is because dry air draws moisture from the skin, eyes and mucous membranes, where it is needed for organic functions. Dryness in the throat, hoarseness and the urge to cough are symptoms of excessively dry indoor air.

Dry eyes
Eyes are particularly sensitive to dry indoor air. The tear film has the task of protecting the eye’s surface from environmental influences. If it dries out, this protection is gone. This can result in irritation and inflammation of the eyes.

Danger of infection
Coughing or sneezing spreads virus-laden droplets (aerosols) in the indoor air. These can remain suspended in the air for hours. The longer they remain in the air, the higher the risk of infection. This is directly influenced by the air humidity.

If the humidity is in the ideal range between 40 and 60 percent, most pathogens cannot survive and are deactivated. Therefore, with the right humidity, the risk of inhaling infectious aerosols is significantly lower and the risk of infection is reduced.

Immune system of the mucous membranes of the respiratory tract
The mucous membranes of the respiratory tract play an important role in the immune system. Inhaled foreign bodies and pathogens stick to it and are thus prevented from further penetrating the body. Underneath the mucous layer, there are tiny cilia that pulse about 450 to 900 times per minute and constantly push the mucous layer towards the throat like a conveyor belt.

The mucus, together with the viruses and bacteria it contains, is finally swallowed and thus rendered harmless. However, this requires a moist, flowable layer of mucus. In dry air, the mucus layer also dries out. It becomes hard and tough, so that it can no longer be moved by the cilia. On the other hand, fewer and fewer pathogens adhere to it. If the air in the room is too dry, this key function of the immune system no longer works. The amount of germs, viruses and bacteria to which the organism is exposed increases dramatically with increasing dryness.

Dry skin
The fact that dry air draws moisture from the skin is a well-known problem, especially in winter. Lips become chapped, fingers and the backs of hands dry and cracked. In extreme cases, the skin can even crack and become inflamed.

Air humidification for controlled domestic ventilation
Diffusion humidifiers are ideal for family homes with controlled ventilation to prevent the air in the room from drying out and to create a healthy and comfortable indoor climate. The installation takes place in the technical room and may be carried out quickly and without major conversion work.

Ideally, heat is supplied via the underfloor heating, the heating circuit or the hot water supply. If none of these heat sources is available, the temperature of the humidification water can optionally be controlled by an integrated electric heater.

Diffusion humidification: the principle
The principle of diffusion humidification is based on the natural diffusion of humidity through a waterproof but breathable membrane. This concept is also applied in modern functional clothing to remove body moisture in the form of water vapour. A particularly efficient industrial membrane is deployed for air humidification. This allows the system to be operated hygienically while preventing the air flow from coming into contact with wet surfaces.