Theory
Time allocation: 10 min.
Relative humidity
Humidity is a basic property of air. Air humidity tells us how much water in gaseous form (water vapor) a given amount of air contains. The amount of water vapor varies greatly over time and also differs from place to place. In meteorology and climatology, the amount of water vapor is of key importance, because the weather and the local climate depend on it.
Relative humidity is the ratio between the amount of water vapor currently in the air and the amount the air would hold at the same pressure and temperature if it were fully saturated. It is expressed as a percentage (%).
The dew point is the temperature at which the air is fully saturated with water vapor (relative humidity reaches 100%).
Source: https://en.wikipedia.org/wiki/Humidity#Relative_humidity
How humidity affects health
The humidity in an apartment or house has a direct and significant effect on the quality of our home environment and, above all, on our health. Experts recommend a humidity of 40% to 60%, depending on the type of room and how it is used; a bathroom or a kitchen, for example, is expected to have higher humidity.