Does A Dehumidifier Kill Mould?

Mould and mildew are extremely common in houses in the UK, this is due to our climate. Wet Springs lead on to damp Summers followed by wet Autumns and cold wet Winters. Wet, damp conditions are the perfect environments for mould and mildew to grow.

This doesn’t only lead to black stains and unsightly mould patches, mould spores can cause ill health including allergies and asthma. Damp conditions and mould can also cause structural damage to your home. But does a humidifier kill mould?

Why Does Mould Grow In Your Home?

Before we can treat this condition we have to understand it as a famous general once said: “You have to understand your enemy to defeat them” or something like that. In this country, due to the wet climate, mould spores are ever-present. All they need is damp, moist conditions and a porous surface to grow on. 

Any room with a humidity over 60% is liable to get mould growth.  60% humidity is not that hard to reach if your windows suffer from condensation, if you dry washing on radiators and cook food without an extractor hood you probably have a humidity higher than 60%. 

Signs Of High Humidity In The Home

The main signs of high humidity in the home are:

  • Damp patches on walls
    Any wall that has a damp patch could indicate that the humidity is too high. But if it’s an outside wall, it could be caused by water running from a blocked gutter.
  • Condensation on the windows
    If your windows are regularly covered in condensation you are probably living in high humidity.
  • A damp smell
    You know that smell that you usually notice in old churches or cellars, well if you have that smell in your home, it’s probably too humid.
  • Discoloured paintwork
    Along with cracked paint, discoloured paintwork is a sure sign of damp.
  • Loose wallpaper
    If you notice wallpaper lifting from the wall, this could also be a sign of damp.

Will A Dehumidifier Kill The Mould?

Operating a dehumidifier in a damp room, or a room with high humidity will help to remove the humidity and the dampness. We know that mould needs a humidity of around 60% to grow but will drying out the air kill the mould?

No, it won’t kill the mould, it will prevent it from growing and keep it in a dormant state, but as soon as the humidity rises again, the mould will regrow. Using a dehumidifier is the first step in killing mould, but it is essential to never allow the humidity to rise to above 55% to prevent regrowth.

How Do You Kill Mould?

The first thing you need to understand is that killing mould is harder than you probably think. The first step is to identify the cause of the humidity, it could be a leaking pipe, insufficient ventilation, drying washing indoors, or many other reasons. Once you’ve dealt with the leak or whatever, the next step is to deal with the humidity by operating a dehumidifier. Then use the following steps to remove and prevent mould from reforming.

How To Deal With Mould


Follow these steps to deal with your mould problem.

  1. Protect yourself
    This involves wearing rubber gloves, a face mask and goggles.
  2. Shut the door in the room you’re treating
    This stops the spores spreading to any other rooms. At the same time, open the windows in the room to allow adequate ventilation.
  3. Remove all soft furnishings toys etc.
    The spores can spread and hide in soft furnishings to reappear at a later date.
  4. Fill a bucket with water and washing up liquid
    Using a soft cloth dipped in the soapy water, gently wipe the mould away. Be extremely gentle as you can easily disturb the mould spores when washing.
  5. Once the mould has been removed
    Dry the wall with a dry cloth.
  6. Dispose of the cloths
    Place both of the cloths used into a plastic bag, tie the top of the bag, and place it in an outside bin.
  7. Vacuum the room
    To eradicate any spores that you have dislodged, vacuum the entire room.

You can buy chemical mould removers but the soapy water works just as well and is less likely to harm animals or children. If the area covered in mould is larger than 1 square yard (1 square metre) you should probably call in a professional.

There is a strong possibility that you will not have killed the mould even after taking the above steps. But once it has been removed and the area has been dehumidified, the mould shouldn’t come back. The problem is, as soon as any humidity over 60% is present in the room the mould will probably reappear.

Frequently Asked Questions

Can mould dry out and die?

Mould can dry out, but it doesn’t die, it just remains in a dormant state. Once the moisture returns the mould will regrow.

What humidity level kills mould?

Lowering humidity doesn’t kill mould, it just prevents it from growing. Anywhere below 50% humidity will stop mould from growing, but as soon as humidity levels rise again the mould will regrow.

Will a dehumidifier get rid of damp?

A dehumidifier will get rid of damp if it’s used for long enough, but you will not stop damp unless you cure the problem that’s causing the damp.

Why is there mould in my bedroom?

There is mould in your bedroom because the humidity in the bedroom is too high.

Is mould worse in summer or winter?

Mould is usually worse in summer due to the damp. In winter low temperatures prevent the spores from growing.

What can mould not grow on?

Mould cannot grow on glass, plastic or metal.

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