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Eight tell-tale signs you have mold in your home

If you detect mold in your home, you’re not alone – it’s more common than you might think, especially in humid parts of the world.

Mold grows in moist environments, so Asian homes are particularly susceptible due to their indoor humidity levels. Whether it's the black spots on your towel, the fuzzy white patches on your kitchen floor, or the slick orange film that forms on your pipes, household mold can be bad news for your family’s health, as well as unpleasant to look at.

What is mold and what causes it? 

Mold is a type of fungus that consists of small organisms found almost everywhere. Outdoors, mold plays an important role in nature, breaking down dead leaves, plants, and trees. It thrives on moisture and reproduces by means of tiny spores that travel through the air. Mold only takes 24 to 48 hours to grow in a moist indoor area.  

Mold infestation will cause the mold spot spreading on your wall

Why does mold grow in my house?

Spores enter the home through the air, like open windows, doorways, and ventilation systems, or by attaching to people on clothing, shoes and bags. The most significant contributors to mold are excess moisture from everyday living and poor ventilation.

You may be surprised to know how much water vapour is generated in the home from essential actions like washing, cleaning and even breathing – the average family of four can produce approximately four pints of water a day. As we can spend up to 90% of our lives indoors, this means moisture needs to be ventilated continuously. Homes with insufficient ventilation will always be more susceptible to mold. Water from faulty plumbing or leaks can also lead to mold if left over time.

Mold can grow anywhere – walls, floors, appliances, carpet, and furniture. It needs moisture to grow, so it is most likely in damp places such as bathrooms, kitchens, laundry rooms, basements, and crawl spaces. For the same reason, homes on lower levels are more prone to mold growth as they are more exposed to moisture evaporating from drains, soil, and the ground when it rains. 

In Hong Kong, due to the high humidity and hot temperatures, the period from April to October is a high season for mold/fungus infestation. Especially during the summer rainy season, mold can spread to the walls, ceilings, toilets or even the whole house within as short as 24-36 hours in a humid environment.

The impact of mold

As well as being unpleasant to look at, mold can also fill homes with a musty, stale smell, sometimes described as being similar to the smell of decaying wood.

It can grow on a range of materials including furniture, due to a combination of excess humidity and poorly insulated exterior walls. For example, when a dresser is placed against an exterior wall, the airflow is restricted, and condensation can form. In time, this condensation creates an environment conducive to mold growth. Mold spores can easily spread to other damp surfaces, including other wood products. Different wood species are affected differently by mold, due to the wood’s stored sugar content.  Any untreated wood can be at risk of acquiring mold without the proper care.

This can wreak havoc on furniture, wallpaper, carpets, and upholstery which will need to be replaced if the mold is not treated early.

If not dealt with, mold growth can have adverse effects on family health, too. People are typically exposed to mold by contact, ingestion, or inhalation. Mold spores and mold have adverse effects on indoor air quality, which is especially dangerous for people with weak immune systems, allergies, or asthma. Some people, like children, older people, those with existing skin problems, those with respiratory problems, and those with weakened immune systems, are more sensitive than others.

Inhaling or touching mold spores can cause an allergic reaction, such as sneezing, a runny nose, red eyes, and skin rash. Mold can also cause asthma attacks.

Learn more about the danger of mold to your family and pets when exposed in the long term.

mold will undermine the health of your family

Eight signs you might have mold in your home

Mold can bloom quickly after the smallest damage, like a leaking shower, condensation under the air-conditioning unit, or water pooling in your crawlspace. But if spotted early, it can be easily treated to minimize the damage.

The eight tell-tale signs to look out for are:

Musty Smell

Have you returned home one day and detected an unusual odour that lingers in the air? Try to examine the corners of your home, or damp areas. These carry a high probability for mold to multiply. The smell of mold is unpleasant, and it will grow stronger over time as the mold starts spreads. “Musty” and “stale” are the most common descriptors of what mold smells like.

Dark spots on surfaces

This might be hard to spot on patterned or dark colored surfaces. Usually, it is more identifiable when it has become a large patch that is hard to miss. During your cleaning regime, try to check the corners or the rim of the surfaces.  If the structure of the wood looks damaged and discoloured, you may have mold.

Black grouting in bathrooms or damp surfaces

One of the most common places to find mold is between tiles, because the porous nature of grout is highly susceptible to microscopic growth. In damp areas, these are stubborn black stains. When cleaning, it is recommended to wipe down dark surfaces with a light-colored cloth to identify signs of mold.  If you notice black, blue, green, or pink growth appearing in water-prone areas, it's a sure sign you have mold issues. Mold can also grow under tiles, weakening their hold and lifting them.

Warped walls

Peeling wallpaper can also be a sign of mold. Unusual surface or peeling abnormalities such as crackling, or bubbling can be a sign of wall moisture. Due to condensation, these are easy places for dampness to occur and breed mold, so do pay particularly close attention to any warped areas of your walls that feel damp.

Feeling fatigue

Do you feel consistent and unusual fatigue? Mold exposure, particularly at home, can cause people to feel tired or develop chronic fatigue. It's due to mycotoxins, which are toxins produced by mold, decreasing oxygenation in the body, among other reactions that cause people to feel tired.  Low energy and fatigue are common mold exposure symptoms.

Allergy or asthma flare-ups

If you have a mold allergy and asthma, your asthma symptoms can be triggered by exposure to mold spores. In some people, exposure to certain mold can cause a severe asthma attack. Signs and symptoms of a mold-induced asthma attack include coughing, wheezing or tightness of the chest whenever you are in your home.

Persistent cough or cold

Mold exposure can also cause coughing, upper respiratory tract symptoms, and wheezing in healthy people. This is one of the telling signs that mold is present in the air particles in your home. Those who are sensitive to mold exposure can also exhibit symptoms such as itchy or red eyes, skin irritation, and a stuffy nose.


Breathing in mold spores can irritate your mucous membranes and immune system, leading to headaches, migraines, and other health issues. Generally, a mold exposure-induced sinus headache feels like intense pressure on your forehead, nose, and inner ear. 

mould reaction

What to do if you have identified mold

With mold, homeowners should always try to prevent it as much as they can.

Keeping indoor humidity levels as low as possible by using a HEPA dehumidifier is key to maintaining humidity no higher than 50% to prevent the growth of pathogenic microbes of mold and to improve your indoor air quality. Rentokil Initial highly recommends the use of an industrial-grade industrial dehumidifier with HEPA filter, as key maintenance after thorough mold remediation.  

Homeowners should also pay attention to ventilation to keep air moving freely, especially in parts of the home that naturally tend to have higher humidity levels like kitchens and bathrooms. If possible, installing exhaust fans that vent outside your home is recommended too, as is drying clothes outside.

Homeowners should fix leaks quickly, add mold inhibitors to paints before decorating, clean bathrooms with mold-killing products and remove or replace carpets and upholstery that have been soaked and cannot be dried immediately. 

Learn more about safe solutions of getting rid of mold

Treat it safely with an expert

Once mold has set in, you might require professional help to remediate it before it spreads further and impacts your family’s health.

Rentokil Initial has a dedicated team of industry-certified mold remediation experts who can assist in surveying and treating any mold within your property.

Check our Mold Removal and Remediation Service.

Wiping out the mold

Our remediation process by our expert professional uses a non-toxic chemical, providing lasting protection against mold and mildew without leaving a harsh odour in your home and safe for the environment. 

Take proactive actions today to prevent mold and preventable hefty costs. Click here to book a survey today and our expert team will get in touch with you.

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