We have repeatedly heard: "absolute" and "relative humidity". What are these indicators? With an absolute value, everything is clear: this is the number of particles of water vapor that is contained in one cubic meter of air. But what practical benefit will the news bring to us that five units of moisture per cubic meter are invisibly present in our environment? After all, we can’t even say whether this air is dry, normal or too damp, because its composition changes at different temperatures. After all, the atmosphere is like a sponge, the warmer it is, the more water vapor dissolves in it. When it suddenly gets colder (for example, on clear nights), the cold squeezes the “sponge” with an invisible hand and dew falls. And the heat, in contact with the carafe of ice water, leaves “evaporation” on the glass.
So, if “5 units per cubic meter” is an absolute indicator, but with respect to the temperature of the medium it can be considered dry (in heat), normal or high (in cold). It is more convenient to use another indicator in domestic needs, namely, “relative air humidity”. At a certain degree of temperature, the atmosphere can accommodate a certain amount of steam. If it is as saturated as possible with vapors, we say that “dampness” is 100%. This, for example, is a Russian bathhouse, where it is hot, but it is also a thick fog, and it is located inside a cloud at a considerable height, where it is cold. That is, the absolute amount of water in the form of steam in a bath, fog and cloud is different, but the water saturation is the same - 100%.
And this relative humidity plays an important role in changing our well-being. Remember how hard it is to breathe and how it tends to sleep before a thunderstorm. This environment is filled with invisible water: its filling increases from normal 50% to 80. But excessive dryness also leads to problems: it perspires in the throat, the body loses a lot of moisture. This is especially evident in the winter in our homes.
Look: the cold enters the room (for example, on the street - 10 C). Even if the relative humidity outside the window is high, in absolute quantity it is low (since it is cold outside). When heated by a stove or central heating batteries, the percentage of water in our environment changes from high to low. If the room is + 25 C, frosty masses begin to literally suck moisture from objects and people in the room. Wooden furniture is drying up, the flowers are turning yellow, and people feel a tickle in their mouth, their lips crack, their skin and hair are dry. It is not easy for those who wear contact lenses in this situation: the eyes turn red, itch. Allergic people also have a hard time - excessive dryness exacerbates the reaction to dust. Therefore, it is advised to put saucers with water near the batteries, although this is not a panacea.
To always be aware of the percentage of water vapor contained in the air, you can purchase special moisture meters, called hygrometers. Indeed, in a damp environment, as you know, microbes multiply. Therefore, outbreaks of epidemics of influenza and acute respiratory infections occur precisely during periods of winter thaws, when the southern wind raises the temperature and increases “sputum”. In the heat, when it “hovers” and stuffy, the number of heart attacks increases, asthmatics have a hard time. With high humidity, cold and heat are more difficult to tolerate than with dryness. The most optimal for our body is 50-60% saturation with water of the surrounding atmosphere.
Using two simple thermometers, you can build your own hygrometer. How to measure air humidity at home, without reagents? We place both thermometers in the shade, however, we wrap the bottom of one of them with a piece of felt dipped in water. Moisture evaporation cools the thermometer. If the relative humidity is high, the felt dries slowly and both thermometers - wet and dry - show the same temperature. And if low, the cloth dries quickly, and the evaporator-coated meter gives lower readings.