Optimal humidity is important for your health and well-being. If the air is too dry, humidifiers improve the air quality and ensure a healthy environment.

A relative humidity of 40 – 60% is recommended for a pleasant atmosphere in the areas we live and work in. Air can become dry, particularly with central heating in winter, when room humidity can often drop below 30%. You can use a hygrometer to measure air humidity (such as Selina from Stadler Form). Typical symptoms resulting from dry air include dry skin and eyes, sore throat, headache and diminished performance.

You can choose between four different humidifier systems: evaporators, humidifiers, air washers and nebuliser humidifiers. Find a detailed explanation of these systems here. Stadler Form offers a suitable product model for all of the humidification technologies. The design humidifiers from Stadler Form ensure optimal air humidity so you feel good in a healthy environment.




Basics of air treatment

Medical professionals recommend a relative humidity of between 40 – 60%. If the air is dry, we suffer from burning eyes, dry skin, irritated mucous membranes, we do not sleep as well and are more susceptible to catching a cold or the flu.

Building materials and interior furnishings made of wood or fabric (e.g. curtains or carpets) absorb lots of moisture. If the air in a room is dry, cracks can form (wood) or an electrostatic charge (fabric) can develop. Musical instruments made of wood can go out of tune if the wood dries out.

Cold air contains less moisture than warmer air. For this reason, humidity in interior rooms often drops below 30% in winter. The greater the difference between outside and inside temperature in winter, the dryer the air in the room is. It is easiest if you measure relative humidity with a hygrometer. Position the hygrometer in the centre of the room, away from windows and doors, and simply read the humidity on the display (e.g. Selina by Stadler Form). You need a humidifier if the humidity is below 40 %. If the humidity is above 60 %, using a dehumidifier is recommended so as to prevent mould formation.

To open the windows does not help to increase the air humidity in the room in the cold half of the year. Regular, brief intermittent and cross-airing is very important for the air we breathe to be healthy (3-5 x a day in winter for a maximum of five minutes). However, airing too often and for too long with cold outside air makes the air in the room even dryer. This also applies to tilted windows. This is because outside air contains less moisture and becomes even dryer as it is warmed up by the heat. See also Why does the air get dry?

Different systems of humidification

All systems have the same goal: to add water to the air and thereby increase the relative humidity. A relative humidity of 40 – 60 % is regarded as pleasant in homes and offices. Measure your humidity with a hygrometer (e.g. Selina by Stadler Form). A distinction is made between two fundamental humidification principles: passive and active air humidification.

With passive humidification, the air absorbs only as much moisture as it needs at the current temperature. This involves applying the self-regulating evaporation principle. In the evaporation process, the dry air from the room is guided over an evaporation filter (evaporator) saturated with water or via moistened evaporator discs (air washer). In this context, the air absorbs only as much water as it needs. The moistened air is blown into the room by a ventilator.

With active air humidification, the current temperature and room humidity are irrelevant. Active humidification systems are vaporisers and nebulisers. The vaporisation principle brings water to the boil and then distributes the hot steam into the room air. The nebulisation system splits water into tiny droplets with oscillations of the ultrasonic membrane, and distributes these as mist into the room air.


The dry room air is guided through the moist evaporator cassettes by a ventilator and absorbs only as much moisture as it needs at the current temperature. The air is optimally moistened and blown into the room.



The water is brought to the boil by means of a heating plate. The hot steam is distributed into the room air.



Air washer

The humidifier discs rotate through the water and absorb it in the process. The dry air is drawn in by the ventilator and guided over the discs. In the process, the air is enriched with moisture and freed from impurities (such as dust, pollen, pet hair and mites) in a natural way.



The water is split into tiny droplets that are subsequently distributed, by a ventilator, as mist into the room where they evaporate. Detailed information about these systems can be found below in the various accordion menus.
If you are not sure which product is right for you, our product advisor is here to help.


Advantages of optimally humidified air

  • Your nose, eyes and skin will no longer feel dry: You will feel more comfortable at home.
  • The risk of catching the flu is reduced: The influenza virus survives for less time in rooms with optimum humidity. The risk of infection is considerably reduced at higher humidities. There will be less stress on your mucous membranes and less chance of you falling ill.
  • You and your family will sleep better: Dry air is not good for you. Enjoy better and more restful sleep when the humidity is optimal.
  • You will be able to concentrate better: You will feel less listless and tired and your ability to concentrate improves.
  • Dust and pollen exposure will be reduced: Even Allergy sufferers can take a deep breath, moist air binds dust particles and pollen.
  • Furniture, wooden floors and paintings will be protected: Cracks and deformation will be avoided.
  • Instruments will not de-tune: You do not need to frequently retune pianos,  guitars and violins.


Measure humidity in the air

It is important to measure the relative humidity correctly. A digital hygrometer, such as Selina by Stadler Form, can take care of this task. Selina is ready for use right out of the box. Put the hygrometer on a raised surface in the centre of the room away from windows and doors. The sensor needs the first couple of minutes to adjust to the room temperature. Afterwards, the relative humidity is displayed. Medical professionals recommend a relative humidity of between 40 – 60 %.

Dry air in the room manifests itself through irritated mucous membranes, dry skin, cracked lips, burning eyes, electro-statically charged hair, headaches, poorer quality of sleep, cracks in parquet flooring and wooden furniture, musical instruments that go out of tune, etc.

Moist air can be the reason for a bad smell in the room, dark marks on walls and window frames as well as water droplets on walls and windows. Check your walls and furniture (the wall behind a cupboard especially) for traces of mould. It is essential that you contact a specialist to have the mould removed professionally. Black mould in particular has adverse health effects.


Hygienic humidifiers

An optimum relative humidity of 40 – 60 % is required for a healthy indoor climate. Measure this either using the hygrostat that is integrated within the appliance or with an external hygrometer (e.g. Selina by Stadler Form). We recommend the following to ensure that your humidifier remains hygienic:

  • Replace the accessories on a regular basis
  • Fill the humidifier with fresh water on a daily basis
  • Clean the inside and outside of the appliance at regular intervals
  • Decalcify on a monthly basis depending on the water hardness

Air pollution such as household dust, pet hair, pollen and mites can also get into the appliance from the outside. Stagnant water, together with the contamination from the air, can be a breeding ground for bacteria.

Therefore, in addition to weekly cleaning, also make sure that the accessories on your appliance are replaced on a regular basis so as to reduce the growth of bacteria and germs as well as to maintain a high level of efficiency.

The Ionic Silver Cube™ continually emits precise quantities of silver ions into the water over the course of a year. From the moment they come into contact with the water, the silver ions have an inhibitory effect on bacterial growth and lead to more hygienic humidification.

The Ionic Silver Cube does indeed inhibit bacterial formation, but it is not a replacement for regular cleaning. For this reason, give your appliance a thorough cleaning with a brush on a weekly basis and rinse out the water tank. Depending on the hardness of the water, decalcify the appliance at least once a month and fill it with fresh water on a daily basis.

Regularly replacing the accessories means the following:

Ionic Silver Cube

The lifetime of the Ionic Silver Cube is around one year. Replace the Silver Cube before each new humidifier season.

Evaporator cassettes

To keep efficiency stable and ensure a hygienic humidification, the cassettes should be replaced every two months.

Anticalc cartridge

Effective for one to three months, depending on water hardness.

Anti-limescale ball

The lifetime of the anti-limescale ball is around one year.


Purchasing a humidifier

Buying a humidifier is not so easy. There are many different criteria that can influence the decision to purchase. These criteria are explained in the following text and 10 reasons are given for why it makes sense to use a humidifier to improve the indoor climate.

Room size

The room size is key when choosing the right humidifier. The rule here is that the volume is to be measured and not the area (area in m2 x room height). Generally speaking, manufacturers work on the basis of a room height of 2.5 metres for their recommendation of the room size.

Intended use

Consider where you would like to use your humidifier (e.g. living room, children's room or bedroom). Other criteria are important depending on the room for which you need the humidifier. Our online decision making aid can be found here: Product advisor

Technical equipment

Different technical features are more or less important depending on the purpose for which the humidifier is used. For example, a brightly illuminated LED display is not something you would want in the bedroom. This is why the LED should be dimmable or the appliance should even have a night mode. In a small room it is important that over-humidification does not occur. Therefore choose a humidifier with the self-regulating evaporation principle. Vaporisers and ultrasonic nebuliser need a hygrostat.


In humidifying a room we differentiate between ultrasonic humidifiers, nebulisers, evaporators, vaporisers and air washers. Each system has its advantages and disadvantages. This is why you should allow yourself enough time when making the decision. In this section you can find an overview of all the systems.

Water hardness

Water can be divided into four different levels of water hardness (°dH = german degree of water hardness):

  • Soft (as of 4 °dH)
  • Moderately hard (as of 7 °dH)
  • Rather hard (as of 14 °dH)
  • Very hard (as of 21 °dH)

Vaporisers and ultrasonic nebulisers are not suitable for very hard (calcareous) water. This also applies if water from a decalcifying system is used.

With regard to water from decalcifying systems, salt is added to the water to reduce limescale (ion exchanger). Salt alters the boiling point. This leads to overheating and to deformation of the vaporiser. With regard to ultrasonic nebulisers, the salt added is finely atomised and results in a disruptive white deposit.

We recommend using an evaporator or air washer for water from a decalcifying system and for hard water.


Maintenance requirements are higher for hard water than for soft water as decalcification is required more often. A thorough cleaning is indeed imperative in all cases to prevent the growth of germs and bacteria. Purchasing an appliance that can be cleaned without any difficulty is therefore recommended. Accessories, such as a decalcifier cartridge for the ultrasonic nebuliser or a filter mat for the evaporator, should be taken into account when calculating the purchase price as they have to be replaced from time to time.

Power consumption

When the air is very dry, you switch on the humidifier constantly where possible. Nevertheless, you can still control energy consumption: Whether the appliance has a hygrostat or not is crucial. The hygrostat can be used to set the desired humidity. The humidifier shuts off as soon as this is reached. The different systems also differ in terms of their respective power consumption: a vaporiser consumes lots of power whereas an evaporator requires little energy.


If a person responds very sensitively to sound, we would advise against purchasing an ultrasonic nebuliser or vaporiser. With regard to the ultrasonic nebuliser, the vibration of the membrane creates what is often regarded as an unpleasant quiet humming noise. With regard to the vaporiser, the "bubbling" of the boiling water may be considered annoying. Our evaporators make the least amount of noise.

Dry air primarily develops in winter when significant heating takes place and room humidity often drops below 30 %. Opening the window does not help, and it even has the opposite effect. The precise explanation of relative humidity can be found here

  1. Fewer colds
    Our mucous membranes need a certain amount of moisture in order to not become inflamed during winter. If the air is too dry, this puts stress on our entire immune system in the long term.
  2. Restful sleep
    Dry air can be a cause of restless sleep as the whole body is under greater strain than it would be were the humidity optimal (40 – 60 %). It is mainly babies and small children who respond very sensitively in this regard.
  3. Reduced allergy risk
    Pollen and dust bind more easily in moist air, become heavy, and fall to the ground. This prevents them spreading and so fewer irritations arise.
  4. No nose bleeds
    Nasal mucous membranes suffer in dry air and are more susceptible to nose bleeds.
  5. No dry eyes
    In winter, we often wake up with itchy or burning eyes, or eyes that are stuck shut. This is a clear sign of dry air. A humidifier quickly and efficiently solves this problem.
  6. Better skin
    Our skin requires a good basic level of moisture. In addition to the appropriate cosmetic products, a healthy humidity is indispensable to keeping the skin firm and healthy.
  7. Gentle ambience for wooden furniture and flooring
    If the air is too dry, the moisture is drawn from solid materials such as furniture, walls and flooring first of all. As time goes by, wooden furniture and equipment parts become cracked and brittle. The right humidity can counteract this. Retailers of wooden flooring often recommend a certain humidity (between 40 – 60 %) as otherwise the quality of the floor can no longer be guaranteed.
  8. Less dust and static charge
    The moist air ensures that less static charge occurs. This means less static in hair and from clothing.
  9. Healthy house plants
    The soil is a good reservoir for moisture. If the air is too dry, then moisture is also taken from the soil of the house plants from time to time. This leads to drying up occurring faster.
  10. Instruments are not put out of tune
    Instruments such as pianos, guitars, violins and other stringed instruments do not go out of tune so quickly if kept at an appropriate humidity.


Humidification glossary

Relative humidity

Describes the relationship between absolute and maximum humidity in percentage terms. The water quantity actually present in the air is referred to as absolute humidity. Maximum humidity is understood as the maximum possible water quantity in the air at the current temperature. The air can absorb more or less water depending on the temperature. The colder the air, the less water it can absorb – the warmer the air, the more water it can absorb.
50 % relative humidity therefore means that half of the possible water quantity at the current temperature is actually present. 100 % means the air is completely saturated with water which corresponds, in absolute terms, to maximum humidity.

Humidifier performance

Shows how many grams of water the humidifier can discharge into the air in the room in one hour.

Room size

Depending on the system and model, a range of room sizes can be humidified. Please see the manufacturer‘s information. For larger rooms it is necessary to use several devices to achieve the desired humidity level. The area of the room is used to calculate the room size, as well as the height of the room.


The hygrostat can be used to set the desired relative air humidity. The device switches off automatically when the desired humidity is reached. If the humidity falls, the humidifier switches on again.

Germs and bacteria

Whenever water is left standing, germs and bacteria can develop. This problem is avoided with vaporizers, because the water in the device is boiled, but for all other systems we recommend the use of the Ionic Silver Cube™ to inhibit growth.

White Dust

«White dust» occurs with ultrasonic nebulizers because these emit limescale particles into the air. The problem can be reduced by using an anticalc cartridge.

Water Hardness

The composition of tap water differs greatly on a regional basis. If you have very hard water (more than 21 German degrees), we recommend the use of an evaporator or air washer.

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