Which leads to the fact that wet things smell bad

What exactly is fresh air?

We need fresh air to be able to live healthily. Without it, we don't feel well and we may even get sick. So fresh air is essential for us. Many people automatically associate fresh air with special and individual things: One likes the smell of freshly mown grass, the other of fresh sea air. In the countryside, fresh air is also associated with natural odors from the environment. Everyone has their own ideas about fresh air. If you inhale deeply and consciously, you can tell a difference between “normal room air” and “fresh air”. But what exactly makes this difference? Is it just the smell or do other things play a role? Let's start with the smell of air: Humans are able to automatically recognize whether air smells good or bad. This ability to distinguish good from bad smells made it easier for people to survive. It is similar with taste. Bitter is z. B. automatically associated with toxic and thus prevents the consumption of deadly foods. In addition, we are able to assign smells. For example, we can distinguish the smell of a basement from that of a garage or workshop.

humidity however, it can affect our sense of smell, both positively and negatively. If the humidity is extremely low, the mucous membranes in the nose and throat can become dry, which affects the sense of smell. If you are exposed to this dry air for a long time, the mucous membrane can also change slightly and is covered with a small layer of mucus to protect against drying out. This "protection" of the mucous membrane is comparable to a cold and also impairs the sense of smell.

Extremely high humidity can also interfere with the sensation of smell. From approx. 65% - 70% relative humidity you have the feeling that everything is a bit "stale". So we can literally smell and differentiate between fresh and stale air.

Let's look at the topic further comfort at. Comfort is a general expression that says when we feel comfortable. In contrast, one speaks of discomfort when one or more factors do not seem to match or we simply do not like them.

We want to go into these factors in more detail below. As described, we can often "smell" too high or too low a humidity directly. But other senses also play a role: Excessive humidity usually causes us to sweat easily or our clothes and fabrics, such as curtains, duvet covers, etc., feel clammy or damp. The discomfort can even go so far that you get dry and cracked skin or the feeling that you can hardly breathe. Too low a humidity level can lead to exactly this effect when our body tries to counteract the drying out of our skin. In addition, viruses and bacteria can lead to infections more quickly in very low humidity. B. lead the mucous membranes. Illnesses therefore have an easier game. We devote an entire chapter to the topics of humidity, condensate and their effects.

Another important comfort factor is that temperature. If this is too low, it is too cold for us, if it is too high, it is too warm for us. Whether we perceive the temperature as too warm or too cold also depends on our gender and our personal comfort temperature. Men have more muscle mass than women. Muscles, in turn, generate heat even when you are not moving, which means that men, on average, do not get cold as quickly as women. If you add the personal feeling, it can come to completely different feelings of comfort.

Moving air is Another factor that is often not or only insufficiently taken into account. We usually speak of (uncomfortable) drafts. Everyone knows the feeling when you are cold and you have the feeling that a window is open somewhere in the house. Often, however, even small air movements are sufficient, e.g. B. in front of a closed window to create this feeling.

Based on these factors, a comfort diagram was developed with various test persons. For this purpose, different temperatures were combined with different humidity levels and drafts of different strengths. If more than 20% of all participants felt uncomfortable, the diagram was adjusted accordingly. 80% of all respondents were of the same opinion. The other 20% do not, which shows that not everyone can always feel comfortable under the same conditions. However, this also means that on average 20% of all people still feel uncomfortable in one place, although the comfort criteria (sometimes referred to as the comfort criterion) are met.


The present diagram is to be understood in such a way that we always feel comfortable when there is air humidity and a certain temperature exactly when the intersection of the two values ​​lies in the blue, i.e. in the comfort range. The orange area is a bit worse and it is not recommended to stay under these conditions for a long time. If the intersection is outside the marked areas, we can almost certainly assume that we will not be comfortable.

If there is a draft (red line), we feel uncomfortable even faster. The colder it is and the lower the humidity, the faster a small movement of air can make us no longer feel good. The area above the red line (including the previous area of ​​comfort) is now just as uncomfortable.

Finally, another important point has to be considered: We humans are creatures of habit and quickly find things good that we have already done many times or that we know from the past. So it is z. B. So that we associate fresh air in the house with certain learned qualities.

For most people, fresh air is cool, for example, because we mostly didn't get to know heat recovery devices or preheated air as children or when we were growing up. Instead, a window or door was opened and air rushed into the apartment. Most of the time this air was cool, either because it was colder outside than inside, or because it just seemed to us that the outside air was less saturated with moisture. Perhaps more importantly, the fresh air always flowed from the direction of a window or door. So we automatically associate fresh air with a window or door, or at least with the direction from which the air is coming.

Ventilation devices can give fresh air completely new properties. Fresh air is no longer necessarily cool, is sometimes even humidified and comes from a completely different direction than our body might expect. So it can be that we get fresh air from the outside, but not perceive it as fresh air and thus cannot recognize it. What this then exactly means and why, precisely for this reason, modern ventilation devices often do not provide the benefit as calculated in practice, is shown in another paper.

Let's summarize:

So fresh air is something that we (mostly) associate with something positive. Starting with a “good” smell, through low air humidity, to (pleasant) coolness. We usually notice when the air is used up and we need fresh air again. Possible negative properties such as pollen or the like. let's leave it out. Fresh air is important to us all because it is jointly responsible for our well-being and our health. But it is also important for maintaining the value of our houses and apartments. We will deal with this topic in another article.