Humidifier buying guide

Humidifier buying guide

Anne, Painter, Cambridge

Guide written by:

Anne, Painter, Cambridge

35 guides

Humidifiers are used to add moisture to dry air to avoid breathing and skin issues. These devices are particularly useful in the winter when your heating dries out the air or in rooms such as nurseries. From cool mist and warm mist humidifiers to ultrasonic or UV models, read on to find the right humidifier for you.

Important features

  • Cool mist humidifier
  • Warm mist humidifier
  • Ultrasonic humidifier
  • UV humidifier
  • Essential oils
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Why use a humidifier?

Rebalancing the humidity levels in your home

Performing the opposite role of a dehumidifier, humidifiers are designed to generate moisture and help restore optimum humidity levels indoors.

The average indoor humidity rate generally ranges form 40% to 60%. However, when the heating is switched on over the winter, this rate can often fall to below 30%. Low humidity can result in a variety of health issues including chapped lips, sore throat, irritated eyes, sinusitis and respiratory problems. Humidifiers help to alleviate these symptoms by combatting dry air which can improve everyday comfort and quality of life in general.

Choosing the right humidifier


When selecting a humidifier, pay special attention to the following: 

  • moisture capacity, based on room size;
  • the sound level, measured in dB;
  • operating life, depending on the size of the reservoir;
  • operating mode, either manual or automatic (via  a humidity sensor).   

It's worth noting that the manufacturer's indications will note the maximum volume covered by the device. There are a few different types of humidifier, each with its own strengths and weaknesses:

  • evaporative cool mist, the most common type;
  • warm mist, allows you to diffuse essential oils, helps to reduce germs and bacteria;
  • ultrasonic, the quietest type, emits liquid water vapour into the air;
  • UV, less common and more expensive but emits healthier water vapour. 

There is also a range of additional options for greater user comfort:

  • timer and programmer;
  • automatic empty reservoir turn-off;
  • essential oil diffusion for ultrasonic and warm mist humidifiers;
  • built-in light;
  • mister.

What are the different types of humidifier?

Cool mist humidifiers


Cool mist, or evaporative, humidifiers work using the process of evaporation. The machine draws in ambient air before sending it in a continuous stream over a water-saturated filter, or wick, which works to vaporise the moisture. The main drawback of this system is that any impurities in the water are pulled in then diffused around the room. As such, it is recommended to go for a model equipped with washable filters or to choose a model with antimicrobial features. Using just 18W of energy on average, these devices are economical but are generally restricted to home use.

Warm mist humidifiers


Warm mist humidifiers operate using a heating system that brings water to a boil and sends it out as a gentle steam. The boiled water is free from bacteria meaning that these models do not require any filters. Furthermore, the warm air will evaporate quicker meaning you'll be able to feel the effects of the humidifier faster.

However, be sure to consider the water type where you live. These devices work better with soft water; hard water will quickly clog them up. They may also increase the room temperature slightly. Warm mist humidifiers can also be filled with essential oils as long as you take care to use the right amounts; this option is not recommended around young children due to the risks of burns. While these models are much quieter than cool mist humidifiers – as they do not feature a fan – they can still emit a rather unpleasant noise during the boiling cycle. As such, it's best to avoid using them in the bedroom.

Ultrasonic humidifiers


Ultrasonic humidifiers are the quietest models available making them particularly to handy for a nursery. High-frequency sound waves (which are almost inaudible) vibrate a metal diaphragm contained within the device. The water bursts and turns into microscopic droplets which are then propelled into the air by a fan. This system has one small disadvantage: the minerals contained in the water are also released into the air. It is therefore best to choose a humidifier with a descaling filter or to use distilled water to purify the air. Similarly, the humidifier should be cleaned regularly. These devices may also decrease the temperature of the room slightly.

UV humidifiers


UV humidifiers use UV rays to destroy any bacteria present in the water. They come in both warm and cool mist models and are especially recommended for children or adults suffering from immunodeficiency disorders. The downside of these humidifiers is that UV lamps have a fairly short service life meaning they will have to be changed after just a few months of use.

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Humidifier characteristics

Humidifier flow rate


The flow rate of your humidifier relates to the amount of water vapour it sends out. The higher the rate, the quicker the moisture is released into the air.

This rate will depend on the volume of the room you want to humidify; the greater the volume, the higher the humidifying capacity must be. This rate is usually provided in cubic metres.

Humidity settings

Humidity settings allow you to set your desired level of humidity according to specific rooms. Some automatic models have a humidity sensor which automatically stops and starts the device when your room reaches your set humidity rate.

Operating time

The length of time your humidifier will run for is determined by the capacity of the water tank; the greater the capacity, the longer the running time. Most devices automatically go into standby mode when the tank is empty and feature a warning light that lights up when they need to be refilled.

Additional options for humidifiers


Depending on the model you go for, there may be a number of additional options available for enhanced comfort:

  • timer and programmers - used to programme different start times and mode cycles; 
  • ionising mode - to neutralise odours;
  • anti-bacterial system - to slow down bacteria growth;
  • digital display of water level;
  • LED warning light to indicate automatic stop in case of empty tank;
  • fans - with two, three or four speed modes for different humidification rates;
  • control panel with digital display - to adjust set humidity rates and fan speed;
  • essential oils - for enhanced well-being.

How to use and care for a humidifier

Using your humidifier 

  • Place the humidifier in the middle of the room for better distribution of water vapour. Set it down on a flat and stable surface. 
  • Do not place your device on a radiator or too close to a wall or curtain to avoid moisture build-up.
  • After the first use, rinse the water tank to eliminate any residue from the manufacturing processes.
  • If possible, used purified water to fill the reservoir.
  • Be sure to clean the device regularly to avoid bacteria build-up.
In addition to using a humidifier, don't forget to air out your rooms for around 10 minutes each day to renew the air in your house.

Cleaning a humidifier

  1. Rinse the filter to remove any impurities.
  2. Wash the water tank. It is strongly recommended to use a specialist cleaning product to prevent microbe development.
  3. Wash the outside of the humidifier with a sponge.

Disinfecting a humidifier 

  1. Clean your humidifier on a regular basis.
  2. Fill the reservoir with a vinegar-based water solution (15% vinegar).
  3. Run the humidifier outdoors for an hour. 
  4. Rinse the reservoir and fill it with water.

Preventing bacteria growth

  1. Clean the humidifier every three days with a white vinegar solution.
  2. Clean and disinfect the device every two weeks

More information

Follow the links below for advice on related accessories and more helpful guides:

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Guide written by:

Anne, Painter, Cambridge, 35 guides

Anne, Painter, Cambridge

After 8 years of trade, I turned professional: I trained myself to be a painter and carpet layer either solo or with 16 years old comrades. 9 months later, following vocational school, my registration in Trades Directory, and the label ‘Artisan’ in hand, I created my company. And since then, I don’t even touch my brushes. I’m a self-taught DIYer and decoration enthusiast, I love to find and restore furniture and to create unique decoration elements. I completed the restoration of my sister’s house, this was last summer, with my niece: electrical, tiling, finishing, plasterboard...we did it all. And today, if I can share my experience I'm happy to do it. A total DIY enthusiast joke: ‘What’s the difference between a clown and a DIY enthusiast? A sense of humor.’ Good Luck.  

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