Articles » About humidity

Practically . . .

26/08/2011

Having understood what humidity is, let us see why it is so important for our well-being. Our body is a very delicate machine which, to function properly, must maintain its internal temperature as constant as possible. When the temperature increases, our body reacts with various countermeasures which would require a ponderous medical treatise to explain in full. We will limit ourselves in observing that the main way of expelling excess heat is through the skin. When a greater quantity of heat needs to be expelled perspiration comes into play: with perspiration the skin is made humid and when it comes into contact with the air it tends to dry. Evaporation requires a large amount of heat which is taken from the skin and so also from inside the body, which can thus re-establish the correct temperature. All this is very efficacious if the humidity in the air is low enough to guarantee rapid evaporation of the perspiration and therefore efficient cooling. Otherwise the perspiration stays on the skin and the body temperature increases causing a sensation of tiredness typical of stuffy days. Excessive perspiration also causes a loss of mineral salts that further aggravate the situation.
Low humidity also can be harmful since excessive evaporation can irritate the mucous membranes of the nose and bronchi.
Following recent studies, for a person engaged in sedentary activity and wearing light clothes, the ideal conditions of well-being occur when the environmental temperature is between 23...25 °C (73,4...77 °F), and the relative humidity is between 40...60% R.H..
Most of the materials are also sensitive to humidity. Because of excessive humidity metals tend to oxidise, leather, fur coats, fabric get mouldy, not to mention certain food products, furniture, paintings, frescos which deteriorate faster, and because of the moulds the rooms become unhealthy.
In other cases, instead, it is the lack of humidity that may create problems. This is, for example, the case of textile industries where, if the air is too dry the threads used for weaving become fragile and so the machines cannot operate at the right speed, or again, the large refrigerator warehouses which store vegetables or fruit which, when there is a lack of humidity, lose weight and wither away. A low percentage of humidity favours the formation of electrical charges that, besides causing the well-known "shock" when metal parts are touched, can also cause various other inconveniences in some industrial processes..
Other situations requiring a high percentage of humidity are the hothouses for growing flowers or mushrooms, etc.
At this point it is clear that very often humidity control is necessary not only for the well-being of human beings but also for technological needs.
To control air humidity, studies have been conducted on appliances that can produce humidity (HUMIDIFIERS), as well as appliances for reducing it (DEHUMIDIFIERS) and instruments capable of controlling the humidifiers and dehumidifiers to maintain the desired environmental humidity constant (HUMIDISTATS).
Air humidifiers can be divided into two main categories:
- Adiabatic humidifiers
- Steam humidifiers
Air dehumidifiers also are divided into two main categories:
- Cooling cycle dehumidifiers
- Absorption dehumidifiers
The choice of the appliance most suitable for a particular application depends on different factors, both environmental and technological and so it must be chosen with the help of an expert technician skilled in the field.

Practically . . . Practically . . .