Selection

The most important things to consider are the size of the area the appliance is designed to cover, its performance and, consequently, electricity consumption, as well as the noise level it generates. The sound or noise level of these devices ranges from 25 to 50 dB.
You are also advised to assess the water consumption and the size of the water tank – the ratio between them determines the time of humidifier operation until the next refilling of the tank (usually 10–15 h).
If you plan to use the humidifier in several rooms, the device should be as light as possible to ensure that it is easy to move.

There are basically three types of humidifiers:

Type	Advantages	Disadvantages
Traditional humidifiers suck the air into the appliance and filter it through water by trapping tiny particles of bacteria, allergens and other pollutants.	Easy to use. Any water (not just distilled water) can be used. Comparatively low electricity consumption.	Evaporation filters must be cleaned or replaced regularly. Noisy. Often they can only operate in a small part of the room.
TSteam humidifiers use the principle of heating the water, which is then released into the room as steam.	Easy to use. High performance.	Unsafe for children and pets due to the possibility of scalding by hot steam. Comparatively high electricity consumption.
Ultrasonic humidifiers – ultrasonic waves create a mist of water without forming condensation or raising the room temperature.	Convenient and safe to use. Quiet and efficient, they use up to 80% less energy than traditional steam humidifiers. A built-in hygrometer or hygrostat maintains the humidity level in the room.	At least filtered water should be used, preferably – distilled.

Ultrasonic humidifiers with both hot and cold steam systems are available for purchase. With the use of a hot steam system, the water is heated to about 80 degrees, then it is turned into mist, and when it reaches the humidifier opening, the steam is about 40 degrees hot, which is a pleasant level of heat that cannot cause scalds. In a cold steam system, on the other hand, the water is not heated and is immediately turned into a moist mist. Some models also offer the option of using the device as an essential oil diffuser.
Cold steam humidifiers are generally cheaper, easier to handle and often suitable for larger rooms. However, they are often louder, as well.
Meanwhile, hot steam humidifiers are quieter, they can increase the humidity level in a room faster and are more suitable for northern climates. Furthermore, hot steam models do not need to be cleaned as often.