7 Common Kinds Of Mould

Mould is one of those unavoidable, inescapable things 90% of homeowners fear, and rightly so, given it’s severe, damaging impact on your health and home. In fact, it’s such a dangerous issue that some of the most dangerous moulds such as black mould has been classified as a biohazard by many, including experts like the CDA.

Regardless of the type of mould you end up identifying, all moulds have some things in common, such as their classification as fungi, need for moisture and warm temperatures (perfect growing conditions here in Singapore!), and finally their presence in virtually all buildings that all humans habituate in.

Some moulds are unsightly but are common enough and ultimately fairly harmless to your health, such as blue stain mould. Hence, we created this article to help you differentiate between the different types of mould, and to know when to seek a professional mould removal service like Zenith Lab. This is not an exhaustive list, but it will hopefully be good enough to help you with your mould removal.

Before we start, we’d like to emphasize that a lot of mould is fairly similar in appearance, and you may end up mistaking a dangerous, highly toxic black mould for a harmless one or vice versa. When in doubt, always seek out a professional mould service – it may keep you and your family safe.

Now, let’s continue on with our 10 types of mould. This list goes roughly from the least harmful to to the most.

1. Alternaria

Alternaria mould (or fungi) is known to be a major plant pathogen, and are involved in the decomposition of various organic matter. It tends to damage crops, so watch out for it if you’re a plant lover or have plants in mould vulnerable areas.

Alternaria mould on a plant leaf.

As you can see, alternaria mould has a velvety texture with “dark green or brown hairs“.

Besides being found on plant leaves, this mould can also typically be found in showers, bathtubs, and below sinks. It often signifies water damage, and it spreads quickly, so it’s important to find and fix it as soon as possible.

As if it wasn’t bad enough, it’s also allergenic, which means that it can cause common allergy symptoms for you(such as coughing and sneezing, breaking out in hives or itchy and watery eyes). It’s the most common allergenic mould, so if you see a velvety mould with dark hairs, there’s a good chance it’s alternaria. Not deadly, but may cause allergies to flare up.

2. Aspergillus

While aspergillus sounds oddly similar to the vegetable asparagus, rest assured that there is no connection between these two items.

Aspergillus is an allergenic mould like alternaria and comes in a long flask spore shape. There are actually 185 different fungi categorized as aspergillus mould, so there definitely is a large variety of colours that all share the same shape.

Aspergillus fungi close up

Aspergillus isn’t super dangerous, and having it present in your home generally isn’t going to cause serious health issues for you. However, it’s still important to watch out for it and nip it in the bud, especially if you’re immunocompromised or have young children at home.

3. Trichoderma

Trichoderma fungi under a microscope

Trichoderma is a mould that usually appears to us as green and white woolly patches – think of how mould grows on old, uneaten grapes and it’s pretty much the same texture and colour. However, there are 5 different subspecies, so coloration may differ slightly. Like the first two above, this is also an allergenic mould and creates similar symptoms.

Look for it’s presence in moist areas, such as wet towels left in the bathroom, behind your wallpaper (if your wallpaper is “bulging”, this is a common culprit), carpet, and other damp areas where moisture may gather, such as around air conditioners or water kettles.

4. Penicillium


If this name sounds familiar to you, that’s probably because you’ve also heard of penicillin, the drug. This mould is particularly interesting – it’s the same mould they use to make penicillin, the accidental discovery that became the world’s first antibiotic.

However, the fungi itself in this raw farm is in fact harmful to your health, more so than the first three. This allergenic mold presents with a velvety texture, and a blue or green colouration. If you’ve ever had a flooding in your house or even a bad water spill that was never fully cleaned up, your house is at risk for penicillium.

Penicillium also spreads quickly, and spreads mould spores in your home or workplace which are small enough to be inhaled. This causes respiratory problems, pulmonary inflammation, asthma, and potentially chronic sinusitis. If you suspect you’ve got penicillium, move quickly to clear it up.

More dangerous moulds:

Now, we’ll talk about the more dangerous (albeit slightly rarer) moulds. These ones need immediate addressing, or you could find yourself with severe health troubles.

If you suspect you’ve got any of these, do not try to DIY it. We mean it. Call a mould professional immediately, who will remove it for you in a safe and effective manner.

5. Black mould

Dangerous black mould

This is the dangerous black mould that caused the classification of mould as a biohazard by the CDA. The scientific name for it is “Stachybotrys chartarum”, and it’s ominous as it sounds.

It appears as dark black or green, with a slimy, mossy sort of texture, and has a nasty habit of appearing across walls and especially above doorways or air conditioners – anywhere that stays wet or humid for weeks.

To further illustrate how bad this is, the writer of this article once visited a friend who had a serious black mould issue. Within a few minutes of entering, they were coughing badly enough to leave.

Other effects also include trouble breathing, fatigue, sinusitis, and depression. Neurological problems and pulmonary bleeding in children and infants has also been caused before.

6. Mucor

Most allergenic moulds are not very dangerous – an itch and a cough for most. However, mucor is an allergenic mould that bucks that trend.

Growing quickly in thick patches, it tends towards a white or off-white appearance. It is usually found on air conditioning units, HVAC ducting, and old & damp carpets. It has been noted to cause asthma and flu symptoms.

In severe cases, there have also been reports of mucormycosis—a dangerous fungal infection which infects and damages your eyes, nose, sinuses, lungs, and brain. In other words, completely nasty.

7. Acremonium

Acremonium is quite distinct and easy to spot, which is really lucky considering it’s severe and damaging health effects.

Starting off as a small, white, harmless looking mould on your walls, it rapidly turns into a white powdery substance. If you’ve ever touched your walls and had your fingers come away white, acremonium is a likely culprit. Sometimes, it is pink, grey or orange.

Typically, this dangerous mould grows in home systems like humidifiers, cooling coils and window sealants. It is also sometimes known to grow alongside strachybotrys (black mold), which makes it a particularly nasty combination. Prolonged exposure to this mould can result in bone marrow and immune system diseases, as well as impaired brain function.

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