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What Is A Dehumidifier?

What Is A Dehumidifier?

The internet seems to be flooded with pages and page of results telling us the benefits using a dehumidifier in the home can have but nothing about what they are or how to recognise you might need one – until now anyway.

Find out what a dehumidifier is, when to use one and the difference between a dehumidifier and humidifier.

Dehumidifiers Explained

A dehumidifier is an electrical appliance that controls and maintains the level of humidity in the air in a home, usually for health or comfort reasons, or to eliminate condensation and prevent the growth of mould, dehumidifiers extract water (often referred to as moisture) from air that passes through the dehumidifier to create a healthy living environment.

There are two main types of dehumidifiers commonly found in homes across the UK – compressor dehumidifiers and desiccant dehumidifiers.

Compressor dehumidifiers remove water through becoming the coldest object in a home. Similar to how a fridge does, as the air passes through the dehumidifier, it comes into contact with cooled coils which use the process of condensation to pull moisture from the air. The collected moisture remains on the coils and drips into a tank at the bottom of the dehumidifier before the remaining clean air is reheated and redistributed back into the home.

Desiccant dehumidifiers remove water through natural absorption. There is no use of a cold surface while removing water from the air. Instead, it works just like a sponge and soaks up the excess moisture from the air. This kind of dehumidifier uses a chemical substance called a desiccant – hence the name – that attracts the water from the air where the moisture is held until it is reheated and regenerated using a small heater inside the machine.

When You Should Use A Dehumidifier

A dehumidifier should be used as soon as signs of damp, such a condensation on windows start to appear. If left unsolved, the build-up of moisture will cause a range of problems that can damage furnishings, fittings and even affect the health of people in the home.

There are five telltale signs to look out for when looking to see if the air in a home is too humid:


Often the first sign of a moisture problem in a home, condensation happens when a home has too much moisture within it. Presenting itself as drops of water on windows, walls and other surrounding surfaces, condensation is a common problem for many homes across the UK and is easily controlled with the use of a dehumidifier. A dehumidifier will not only control and maintain the excess moisture and humidity level within a home but prevent greater complications a build up of moisture will create such as mould and mildew.


Found most often in bathrooms and en-suites, mould stains appear as little black spots on ceilings and tiles that surround baths and showers as a result of the steam bathing and showering produce. As this steam rises, it should be ventilated out with an exhaust fan but if there is a lack of adequate ventilation, this will create the perfect breeding ground for black mould and should be fixed as soon as to minimise health risks and stop the problem coming back. Make sure an exhaust fan is running during and after each bath or shower and fix other ventilation issues. A dehumidifier can also be used and will lessen the amount of moisture that hangs around in the room.

Unpleasant Odours

There’s nothing less inviting than walking into a home with an unpleasant musty smell. From cooking and pets to mould and smoke, there are a variety of things in the home that can create odours that permeate the air and linger until solved. Overall, these unpleasant odours can be eliminated through good ventilation, well-conditioned and designed dehumidifiers. A dehumidifier will get rid of excess moisture will keep the level of humidity down which is ultimately the main goal when wanting to combat the unpleasant musty smells everyday activities in the home produce.

Water Stains

Water stains on walls and ceilings is another symptom that there is a moisture problem in a home and should be looked into immediately to avoid further complications. The longer the stain is left alone, the more damage will continue to spread and become permanent. However, once the cause of the stain has been repaired, ensure that it doesn’t return in the future through keeping moisture levels to a minimum; a dehumidifier is a great first step to stop more damage from being done.

Heightened Allergies

For those who suffer from allergies or asthma, dust mites and mould spores which thrive in warm, humid environments with lots of moisture, trigger the same symptoms as outdoor pollen. Using a dehumidifier will not only remove allergy triggers from the air through filtering the air and reducing the level of moisture but minimise exposure to the growth of allergens, bacteria and pollutants that heighten symptoms.

Dehumidifier Versus Humidifier

A dehumidifier and humidifier both help improve the quality of air in a home, the main difference is how they work. If the air in a home is too humid, a dehumidifier is used to take moisture out of the air, where a humidifier adds moisture into the air by releasing water vapour when the air is too dry.

When You Should Use A Humidifier

Humidifiers add moisture into the air which can benefit those with dry skin and respiratory symptoms. In colder months the result of dry air is that it can cause moisture to evaporate from our bodies through the skin and respiratory symptoms to worsen over time because it dries out the lungs, nasal passage and lips. Using a humidifier can counteract these problems and help people with chapped lips, dry skin and irritated eyes by turning water into breathable vapour that acts as a moisturising agent to relieve dryness.

When You Should Use A Dehumidifier

Dehumidifiers remove moisture from the air which results in the growth of condensation, dust mites and mould which aggravate allergies and asthma as well as skin irritation and respiratory symptoms that are triggered by an unhealthy amount of moisture in the air. Using a dehumidifier can eliminate this threat and many others like we spoke about previously (see section When You Should Use A Dehumidifier).

Above all, the relative humidity of a home is the deciding factor in selecting whether a dehumidifier or a humidifier is required. The humidity level of a home can be checked with a hygrometer, which will read the moisture level in the air and give a heads up to make any necessary changes. However, the relative humidity should always be between 35 to 50 percent, anything above or below could have a negative impact on the quality of indoor air.

In Summary

A dehumidifier controls and maintains the level of humidity in the air to leave the home feeling healthier and more comfortable while noticing fewer physical signs of damp air – such as condensation and mould. No matter how big or small the problem is it will develop into greater longer lasting problems that get harder to control, maintain and prevent if left unsolved so it’s time to take control.

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