Dunja Tanner , 03.10.2019

How to choose a humidifier, tips and recommendations to purchase

Anton humidifier by Stadler Form improving indoor climate

Which humidifier should you choose? Purchasing a humidifier is certainly not easy. There are many different criteria that can influence your choice. This purchasing advice explains the points to consider and will help you to choose the right humidifier for your home or office.

A humidifier increases the humidity indoors to an optimum level, so that we and our children feel comfortable and are able to sleep better. When we turn on the central heating in autumn and winter, the relative humidity indoors can often drop below 30%. Doctors and medical experts recommend a level of between 40% and 60% as the optimal humidity for apartments such as bedroom, nursery or living room. This is the level at which we feel most comfortable, enjoy the most restful sleep, our bodies’ resistance to flu is heightened and we are able to concentrate better. We recommend using a hygrometer to constantly check the humidity and to set up a humidifier if you have a level of relative humidity of 40% or less. Learn more in another blog post about why dry air is a risk to health and well-being.

The main selection criteria when purchasing a humidifier

There are various selection criteria that you need to take into account when choosing the right humidifier to meet your personal requirements. We have summarised the three main criteria for you first and then explained further points which could influence your purchase.

Humidifiers come in a range of sizes: compact models with limited water storage capacity and low humidification performance are the ideal solution for smaller rooms while larger models with greater water storage capacity and high humidification performance are ideal for large rooms. Humidifier manufacturers indicate the recommended room size for their devices. First of all, you should measure the area and volume of the room where your humidifier is to be set up. If the doors to other rooms are open, the area of those rooms must also be included as the air will also circulate through them. The room area is calculated by multiplying the length and width of the room (e.g. 5 x 6 meters = 30 m2). To get the room volume, you now multiply the room area by the ceiling height (30 m2 x 2.5 meters = 75 m3). If only the recommended room volume is indicated for a humidifier and not the area, you can normally assume that the manufacturer has based the humidification performance on a ceiling height of 2.5 meters. Now choose a humidifier that is at least recommended for rooms up to your desired room size/area, e.g. if the area of your room is 30 m2, you should choose a humidifier that is recommended for 30 m2 or more.

Perfect room size humidifier by Stadler Form

An important note on minimum energy houses (low energy or passive houses) with controlled ventilation: Controlled ventilation systems have the same effect as open windows. That is why we recommend that you choose more powerful humidifiers for ventilated rooms and calculate double the room size compared to non-ventilated rooms (e.g. humidifiers for non-ventilated rooms of up to 50 m2 and for ventilated rooms of up to 25 m2).

Water hardness is a measure of the quantity of dissolved minerals in water, especially calcium and magnesium. The higher the amount of those minerals, the harder the water. Generally, water hardness is measured in German degrees of hardness (°dH). Why is water hardness so important when choosing a humidifier? We will recommend a particular humidification system according to the hardness of the mains water in each case, because the various technologies and types of device react better or not so well to a high limescale content. There are 4 different types of humidifier: evaporator, ultrasonic nebuliser, vaporiser and air washer. If you don’t know the hardness of your mains water, you can ask your local water supplier. You can often find that information on the water supplier’s website.

Soft water (0°–4°dH)
We can recommend all four types of humidification if you have soft water.

Medium-hard water (5°–13°dH)
All the humidification technologies can also be recommended if your water is medium-hard though in case of ultrasonic nebulisers, the anticalc cartridge should be replaced regularly. This cartridge will reduce the limescale content of the mains water before it is emitted into the room as humidity.

Hard water (from 14°dH)
If you have very hard water, we recommend that you use evaporators and air washers. In case of air washers, the anticalc cartridge should be used and replaced regularly. Vaporisers do not get on well with water which has a high limescale content as a lot of the limescale will collect on the heating plate which will have to be removed regularly. In case of nebulisers, the anticalc cartridge is unable to remove the high percentage of minerals which are present in very hard water. If calcium (i.e. limescale) is nebulised with the water in the nebuliser, it will be emitted as white dust (also known as white deposit) and settle on the surfaces in the room. If you have hard water but would still like an ultrasonic humidifier, we recommend that you mix the tap water with distilled water in a 50:50 ratio to reduce the limescale content in the water.

If your water has a high limescale content, your maintenance costs will be higher than they would be if you had soft water as you will need to carry out descaling more often. However, regardless of your water hardness, it is essential to always clean your device thoroughly in order to prevent the growth of germs and bacteria. That is why we recommend that you purchase a device which is easy to clean.

An important note on water from descaling systems: The operation of water softeners is often based on the principle of ion exchange. This involves adding salt to the mains water in order to reduce limescale. The salt present in the water will settle in the humidifier just as limescale does and will need to be removed regularly using descaler. In the case of vaporisers, it should be noted that the salt will change the boiling point of the water, leading to overheating and deformation of the vaporiser. With an ultrasonic nebuliser, the salt added will be nebulised and emitted as an annoying white deposit. For that reason, we only recommend the use of evaporators or air washers if you have water being emitted from a descaling system.

All humidifiers have the same aim: to add water to the air in order to increase the relative humidity to an optimal level of between 40% and 60%. There are pros and cons with each system and therefore you should take plenty of time when making your decision. There are four different humidification principles.

This technology is based on the natural principle of evaporation. Humidifier filters (also known as evaporator pads, cassettes or filters) suck up water. A fan sucks the dry indoor air through the filters which emit the humidity into the air. The air only absorbs as much moisture as it needs for the current temperature. Excessive humidification is not a worry. Evaporators are very efficient and require very little power. This system is especially energy-efficient and ideal for babies and children as no hot vapour is emitted.

A vibrating ultrasonic membrane turns water into tiny droplets which are then blown into the room as mist by a fan before they evaporate. The visible mist is cold and safe for children. In addition, optimal pre-heating will only heat the mist to a lukewarm temperature. Ultrasonic nebulisers require very little power and have a high level of performance. Because limescale particles will also be distributed in the room along with the water droplets, ultrasonic nebulisers must always be fitted with an anticalc cartridge as well as cleaned and descaled regularly.

Eva ultrasonic nebuliser by Stadler Form distributing mist

Air washers are a combination of humidifier and air purifier. Special evaporator discs absorb the water and a fan blows dry indoor air over the rotating wet discs. The humidified air is distributed in the room. Air washers have a high level of humidification performance and require very little power. In addition, they can “wash” large to medium particles and odours (such as e.g. dust, pollen, pet hair and dust mites) from the air in a natural way.

Water is heated to boiling point inside the device until it turns into germ-free water vapour. That vapour is optimally distributed in the room and a high level of humidification performance is achieved. The germ-free vapour is ideal for allergy sufferers. Vaporisers are very powerful and for that reason, they should always be controlled by means of a hygrostat. As the heating plate will fur up over time, the device will need to be descaled regularly.

Vaporiser Fred by Stadler Form increasing air humidity

Other criteria to be taken into account when purchasing a humidifier

Think about where you want to set up your humidifier (e.g. in the lounge, nursery, baby’s bedroom, office or bedroom). There are also other important criteria according to the intended location of your humidifier. Various technical features will also be considered important according to the intended use of your device. For example, in the bedroom you don’t want the LED display to give out a harsh light. For that reason, the device should have dimmable LEDs or even a night mode. In a small room, it is important not to have excessive humidification. Therefore you should choose a humidifier with a self-regulating evaporator system. Vaporisers and ultrasonic nebulisers require a hygrostat. It may be beneficial for nursery humidifiers to also release an essential oil into the room. For that reason, a lot of humidifiers are fitted with a fragrance dispenser which can be filled with an essential oil.

If your indoor air is very dry, you should leave your humidifier switched on at all times if possible. However, you will still be able to control its energy consumption – depending on whether the device has a hygrostat. The hygrostat can be used to set your desired target humidity. As soon as this has been reached, the humidifier will switch off automatically. In addition, the power consumption of the various systems differs in each case: a vaporiser requires a lot of power whereas an evaporator requires very little.

Which humidifier is quiet enough for the bedroom? We would steer anyone who is highly sensitive to noise away from ultrasonic nebulisers or vaporisers. With ultrasonic nebulisers, the vibration of the membranes create a light hum which could be considered annoying. In addition, a soft splashing sound may be heard by someone with sensitive ears. With vaporisers, the “bubbling” of the boiling water could be considered annoying. Then again, others may find such soft background noises (also known as white noise) calming. The quietest types are evaporators and air washers.

If your water has a high limescale content, your cleaning and descaling costs will be higher than they would be if you had soft water as you will need to carry out descaling more often. Water from descalers will also leave behind deposits in your device (salt rather than limescale). That is why it is important for all humidifiers to be cleaned regularly (preferably weekly) in order to prevent the growth of microbes. Therefore we recommend choosing a product that is easy to clean. For example, air washers which have an additional cleaning mode, make looking after your device child’s play. Accessories such as an anticalc cartridge for an ultrasonic nebuliser or a filter pad for an evaporator, for example, should be included in the calculation of the purchase price as they will need to be replaced regularly.

Do you have any further questions on how to choose the right humidifier for you? We would be pleased to provide you with advice over the telephone, by e-mail or via Twitter or Facebook. Download our air humidifer overview here to see all Stadler Form humidifiers at a glance. Once you have chosen your humidifier, you can purchase it via our webshop or one of our dealers. We look forward to hearing about your experiences.

Want to find out more about the positive effects a humidifier can have on health and well-being? Then read our blog article entitled «10 reasons to get a humidifier».

Watch the following video on «How to choose a humidifier».

Watch the following video on «Perfect humidity level and how to measure it!»


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