We experience high levels of water vapor in the air as sultry. Some people then perspire more quickly. Such high humidity occurs in poorly ventilated shower rooms, in the sauna, or on hot, rainy summer days. Heat and high humidity put considerable strain on our circulatory system.
Very low humidity, on the other hand, is also very noticeable in our own bodies. The skin becomes dry, the mucous membranes of our airways dry out, and some people feel an increased urge to cough.
What is relative humidity?
The ratio of the water vapor present in the air to the maximum absorbable water vapor is referred to as the “relative humidity” (in percent). The maximum absorbable water vapor depends on temperature: more water vapor can be absorbed at higher temperatures.
How do we notice the presence of humidity?
The presence of humidity is readily observable in everyday life in the “fogging up” of drinking glasses containing an ice-cold liquid. A simple explanation for this is condensation: the transition of water vapor from a gaseous to a liquid state on a cold surface. We can also observe this phenomenon on mirrors, windows, and eyeglass lenses, where air due to temperature changes cause the surface to fog up.
And in autumn, we sometimes see haze, where water vapor from the air condenses into tiny droplets that float through the air. The clouds in the sky are also water droplets that have formed as a result of high humidity. And in cold winters, we exhale “fog patches” because the exhaled air has higher humidity than the ambient air.
How can you change the humidity in a room?
- One can increase humidity by:
- hanging wet clothes;
- using electric humidifiers;
- setting up lots of houseplants.
Conversely, regular airing, especially in winter, or the presence of an electric dehumidifier, can reduce the water vapor content in a room.
For optimal humidity control, use of a hygrometer is recommended.
How do we measure humidity?
A hygrometer, derived from “hygro” (Greek for “moisture”) is a measuring instrument we use to measure humidity. Humidity is the amount of water vapor in the ambient air.
The ratio of the actual amount of water vapor to the maximum possible is referred to as the “relative humidity” and is expressed as a percentage. It is also referred to as the “saturation point” in this context. Thus, a relative humidity of 100% means that the air has absorbed the maximum amount of water vapor. The higher the temperature of the air, the more water vapor it can absorb. Air at 10°C can contain about 9 grams of water per cubic meter, at 23°C it is already 20 grams of moisture. The maximum absorbable fraction of water vapor in air depends on temperature.
We know analog and digital hygrometers. With a digital hygrometer, changes in humidity are measured electronically using a sensor.
How does a hygrometer work in the household?
Hygrometers used in the household are based on both mechanical and electronic methods. A well-known variant is the so-called “hair hygrometer.” Hair is a hygroscopic material whose length varies with humidity. The change in length is transferred to a pointer that indicates the relative humidity on a scale. Thereby, the lower the humidity, the more the hair shrinks. Preferably, female hair was used. Today, synthetic materials are also used as replacements for human hair.
In the electronic version, the change in electronic resistance or the electronic capacitance (this involves a capacitor) is measured depending on the humidity.