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How do ultrasonic mist humidifiers work?
16-1-2025
Translation: Katherine Martin
When it comes to humidifiers, you’re spoilt for choice. In my view, you’re best off going for a device that boosts humidity by atomising water.
Dry air’s a problem in winter. Although it doesn’t cause illness directly, it does dry out your mucous membranes, making them more susceptible to viruses and germs. My fellow editor, Stefanie, explains this in more detail here:
In other words, you can stave off illnesses by keeping the moisture content of the air inside your home at an optimum level. That’s somewhere between 40 and 60 per cent humidity (linked website in German). Before you buy one of the 532 humidifiers in our range, you should find out how high the humidity is in your home. You can measure this with a hygrometer. These devices come in all sorts of configurations, from aesthetic to ugly, app-controlled to app-free, pricey to budget-friendly.
Ultrasonic tech generates mist
I bought an ultrasonic humidifier to improve the air quality of my home. It’s fascinating how these devices work.
The core of an ultrasonic humidifier is a piezo, which vibrates in the ultrasonic range (between 20 kilohertz and one gigahertz). It’s inaudible to even the sharpest human ear. Dogs and cats, however, can hear it. So, bringing an ultrasonic device like this into your home might confuse or distress your pets.
The piezo’s super-fast vibrations move the water in the humidifier’s tank onto a special surface or membrane. These vibrations are so intense that they transcend the surface tension of the water, breaking it down into millions of microscopic droplets. Physicists call this process cavitation atomisation. Cavitation is when vapour-filled bubbles form and suddenly collapse. You might recognise the word from The Hunt for Red October, in which a newfangled Russian submarine can only be located by the noise caused by cavitation. But let’s not get on to that...
Ultrasonic humidifiers produce a fine mist consisting of tiny water droplets. These are either propelled into the air by a small fan or released without any mechanical assistance. As the mist’s created by ultrasonic vibration and not by heating the water, it stays cool. It’s completely safe to hold your hand over the mist and feel the temperature.
Incidentally, the mist won’t put your wooden floors or sofa at risk. It stays suspended in the air and increases humidity there without creating damp patches anywhere else. And it certainly won’t make puddles on your parquet flooring.
Advantages over other humidifiers
Ultrasonic humidifiers’ competitors are evaporative humidifiers and steam humidifiers. Both devices have their advantages; evaporative humidifiers only work up to a certain humidity level, so they don’t make the room too humid. Let’s face it, that wouldn’t be healthy either. Evaporative humidifiers need to be fitted with filters that draw the water out of the tank and then release it as moisture.
Steam humidifiers heat water to boiling point without a filter. The steam they produce is essentially germ-free. These humidifiers are often slightly noisier and consume more electricity. Stadler Form’s popular Fred humidifier consumes 300 watts.
Ultrasonic humidifiers are comparatively economical, requiring a maximum of 100 watts. They’re also quiet. The only ones you’ll be able to hear are the versions with a small fan. With this in mind, they’re ideal for living rooms – especially when you’re trying to enjoy the tingly suspense of a film. Or some other tingly activities in the bedroom.
Since the moisture they produce is cool, the devices are safe to use. Kids who’re still exploring the world with their hands won’t burn their fingers, and curious pets won’t end up with singed paws or noses. Ultrasonic humidifiers are fast too. When you switch them on, they boost humidity immediately – and don’t need a warm-up phase.
Usage and maintenance tips
Does this all sound too good to be true? Well, ultrasonic humidifiers have their downsides too. If you don’t clean and disinfect them regularly, they can easily become germ magnets (linked article in German). If you treat them with a mixture of water and white vinegar, you’ll save on the pricey cleaning products that humidifier manufacturers want to sell you.
Another no-no for humidifiers is hard water, a particularly common issue on the Swiss Plateau and northeastern Switzerland. If you live in one of these areas, it’s important to regularly maintain your device. That means filling it with fresh, cold water every day, and cleaning the tank and device frequently to get rid of limescale deposits. Manufacturers are aware of the issue and have taken measures such as building anti-limescale cartridges into their devices. These need to be replaced regularly.
You can also minimise the amount of effort needed to clean your humidifier by filling it with distilled water. Then again, you have to buy that. Alternatively, if you have one, you can use water from a dehumidifier in your communal laundry room, as it’s pretty much distilled.
Don’t put your humidifier near a radiator, fireplace or ventilation system. The mist it produces should be able to circulate throughout the room undisturbed by other air flows. Positioning it on a shelf or dresser is better than putting it on the floor. Speaking of which, I’d better rethink the positioning of my own humidifier. As you can see from the photo at the top of the page, it isn’t set up in a particularly great spot.
It’s crucial that you keep an eye on the humidity. Ultrasonic humidifiers are really effective, causing the optimal humidity level to be reached quickly. If your device doesn’t have an integrated humidistat, you’ll have to remember to switch it off manually. Humidifiers with humidistats save you the bother of checking.
Header image: Martin Jungfer
Martin Jungfer
Head of Content
Martin.Jungfer@digitecgalaxus.chJournalist since 1997. Stopovers in Franconia (or the Franken region), Lake Constance, Obwalden, Nidwalden and Zurich. Father since 2014. Expert in editorial organisation and motivation. Focus on sustainability, home office tools, beautiful things for the home, creative toys and sports equipment.