Let’s discuss one of the important advantages of air humidification — reducing the number of colds. According to various sources, proper air humidification in winter can reduce the incidence of diseases by 1.5–2 times. In addition, the severity of symptoms and the number of days spent in a state of illness are significantly reduced.
Let’s figure it out.
As you know, air is characterized by absolute and relative humidity. Absolute is simply how much evaporated water is in the air (for example, grams of this water in a cubic meter of air), and relative is how much less such water is compared to how much air could hold in itself. The possibilities of air to hold water in itself are not unlimited and have a very specific limit, and this limit depends on temperature. The lower the temperature, the lower (and much lower!) The ability of air to retain evaporated water.
It turns out that if the air is heated, then the absolute humidity will not change, since how much water was in the air, so much will remain. But the ability to absorb water will greatly increase and, consequently, the relative humidity will decrease, which, as we already know, is the proportion of water in the air compared to the maximum possible. This is where the insidiousness is hidden, water does not seem to disappear from the air when heated, and the relative humidity drops sharply.
But why is relative humidity important at all? Yes, because we feel it. It is the relative humidity that determines the rate of evaporation of moisture from the skin, from the mucous membranes, from the hair. And a sharp (many times!) increase in the rate of evaporation plays a key role in all manifestations of “low humidity”.
Now let’s see what happens when we breathe in air? In the airways, it must be moistened, otherwise the lungs will not be able to work properly. In cold weather outside, the air has a low absolute humidity, since in a cold state it cannot hold enough water. When inhaled, such air heats up, this is natural, and its relative humidity drops sharply, as we already know.
Fortunately, the body is perfectly trained to deal with such a situation. To increase the amount of water in the inhaled cold air, the surfaces of the respiratory tract actively begin to secrete sputum. The nose “flows” in the cold, this is an absolutely normal reaction of a healthy body, the lungs are protected.
But in a warm room in winter, the situation is different. The air, heating up in the room, nevertheless retains a low “street” moisture content, there is nowhere for it to absorb water. As a result, the room has low relative humidity, usually 10–20% (with a norm of 35–60%), and the evaporation rate has increased several times compared to the norm. It would seem that there are no problems, because in the cold our body copes with additional moisture when inhaled. But no! Reflex “wetting” of the mucous membranes works at low temperatures, and we inhale already heated air!
From the point of view of evolution, man very recently began to live in artificially heated air, so the body is not adapted to such a situation. From his point of view, if the air is warm, then it is warm outside, and if it is warm outside, then the relative humidity is not low.
Therefore, when inhaling artificially heated air, without adding moisture (while during the natural warming of the weather outside, the air picks up moisture), the surfaces of the respiratory tract begin to dry out, the full-fledged self-humidification mechanism does not turn on. But the mucosa is also mucilaginous, it feels normal only when it is wet. And in a dried one, it ceases to resist pathogens well and cannot effectively get rid of them, since this would require sputum, which is no longer in sufficient quantity on the surface. All! Hello viruses, hello bacteria.
It turns out that the human body is simply not ready for a situation where the inhaled air is warm, but has such a low humidity. There is no such thing in nature, even in the desert. And the main reason for the increase in the number of colds in winter is not the frosty air outside, to which a healthy body adapts perfectly to periodic stay, but a long stay in conditions of low humidity and warm rooms.
Exposure to dry indoor air has a cumulative effect, permanent exposure to such conditions causes harm. Trying to “heal” the room with ventilation only worsens the situation, as the humidity is further reduced due to the abundant supply of low-moisture outdoor air.
Therefore, it is important that as much of the day as possible, both adults and children would be in evolutionary habitual conditions for the body. That is, either in the fresh air, where the temperature and absolute humidity are consistent with each other, or in a warm room, but with humidification working, so that there is no discrepancy between humidity and temperature.
Unfortunately, in Russia the situation with air humidity is especially unfortunate, but the point here is already in cultural differences. We are accustomed to stoking heat and walking at home in winter in light clothes. During the cold season, a 5‑degree rise in room temperature means a decrease in relative humidity by about 10%. The air in our homes is usually drier than in countries accustomed to saving on heating.
The conclusion is simple. Neither good ventilation nor airing will fix the situation. To maintain a healthy indoor climate in winter, it is absolutely essential to humidify the air, and you need to make sure that the humidification system is really up to the task. Well, walk more!
Source: Buhler-AHS Russia