Mold definition, Different Types of Mold

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What is mold?

Firstly, mold is not a single organism. The term mold covers a wide variety of organisms. These all have the fact that they are fungi in common. The mold fungi create multicellular thread-like structures that are called hyphae. When most people hear the word “mold,” they immediately think of a negative. TV, television shows, and ads all claim that mold is a bad thing. But, the reality of what is mold is much more complicated than that. Mold grows from microscopic spores found in the air. These spores occasionally join together, form clusters, and become the eye-sore and potential health hazard in our homes.  Most types of mold thrive in a dark and damp environment. This is why you will usually find mold in attics, basements, bathrooms, and inside walls.

Is mold a Fungus or Bacteria?

Is mold a bacteria? Nope, notta, no way. No doubt about it, It’s a fungus for sure. Bacteria have a simpler molecular structure vs fungus that has a more complex DNA make up. Bacteria will usually be unicellular, single organisms and will not generally grow in strands or clusters like fungus.

Mold vs Fungus

Don’t fall into the trap of thinking that all mold and fungi in general are bad for you. We are familiar with many different types of fungi in our daily lives. Many people eat mushrooms, a type of fungi. The yeast that we use to rise bread products is also a fungus. In fact, molds and yeasts are very similar types of fungi, except yeast is a single-cell organism and mold is a multi-cell organism. Clearly, not all fungi are bad for you and it even plays a role in the health of the environment.

The problem with mold comes when it begins growing inside our homes. Certain types of mold are quite harmful to humans—more on this below. Mold is also unsightly and can discourage people from visiting your home. Finally, the presence of mold often indicates a larger problem, which needs to be taken care of before permanent damage is done to the structure of your house or your family’s health.


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How to clean up mold and what products to use Fungal hyphae
Fungal hyphae mass wild fungus Mushroom Fungus mould vs mold british flag

Is it mould or mold?

When researching mold online, you will likely see two different spellings of the word. The Mold Definition is the American English spelling, while the Mould Definition is the British English spelling. But, do these two words mean slightly different things? How to clean up a moldy water tower

The short answer is no. The difference between mold and mould is purely a spelling one. When referencing the fungus that grows in our homes, these two words mean the same thing.

What is Mould Meaning?

The biggest difference that you will find between mold and mould is that the American spelling has multiple meanings. Mold can refer to the fungus discussed in this article. Or, it could be defined as “a frame for shaping something” or “to shape in a mold.” The British mould meaning and spelling does not have this ambiguity. So, many experts will use the British spelling to make the mould meaning clear.


Are mildew and mold the same thing?

A lot of times the terms mildewy and mold will be used interchangeably. While not completely wrong, this use of the two terms is misleading. Mildew is a type of mold, but not all molds are mildews.

The best way to tell mildew and other types of mold apart is where the fungi grows and how it looks. Most molds will appear fuzzy and will grow on any type of surface. Mildew, on the other hand, grows on wet, flat surfaces and looks powdery or downy.

There are also some big differences between mold and mildew when it comes to the damage they can do to your home. Many types of mold aid in the decomposition process of many materials. This is a problem for your house because if this type of mold gains hold it can begin decomposing the walls and support beams. Mildew does not cause structural damage, only cosmetic. Mildew tends to bring a musty or mildewy smell with it as well, be happy if its just mildew. Mildew is much easier to clean up. Find Our Top Picks for mold and mildew Cleanup.

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Different types of mold

No one knows how many different types of mold there are, but some experts estimate anywhere from ten to three hundred thousand different species. That is an almost incomprehensible number that cannot be covered in just one article. But, here are the top mold varieties that you will likely find in your home.

  1. Aspergillus Definition

Aspergillus is a name that applies to 185 different species of mold. Because of the number of species in this family, Aspergillus mold can be found in any color. But, all of these species have long flask-shaped spores. These will occasionally chain together to form long strands of Aspergillus mold on a surface.

Aspergillus niger is one of the most common types. You have most likely found this on fruit in the home. Aspergillus niger will commonly grow on fruits and vegetables and produce a black mould. This type of mould is most harmful to people with weakened immune systems.

Aspergillus fumigatus is another important mold to be aware since is the cause of 90% of aspergillus related diseases according to this report. The fungus can grow at 37 °C or 99 °F and will vary easily go airborne. This mold alone is the most important reason to keep your home mold free and clean up any contaminated area right away.

All species of Aspergillus are allergenic, but the severity depends on the type and environment of the mold in your home. Occasionally certain species of Aspergillus produce aflatoxins, which are a deadly carcinogen. So, you should get this type of mold removed immediately.

Aspergillus niger

Aspergillus niger SEM

Aspergillus fumigatus

Aspergillus fumigatus 01
  1. Cladosporium cladosporioides

Another mold that can cause allergic reactions, Cladosporium cladosporioides is most common found on upholstery—like drapes or curtains—and carpets. This mold is usually green or brown and has a suede-like texture.


Cladosporium cladosporioides is not known to be toxic. However, you may experience allergic reactions in the eyes, nose, throat, and skin. These issues could progress to asthma attacks and lung infections if the mold is not removed.

  1. Chaetomium globosum

If you’ve ever seen white, grey, or brown mold around water damage in a building, it is likely that it was caused by Chaetomium globosum. Eventually this mold changes color to black. It thrives in wet environments, and most often occurs near water damage.


If you are exposed to Chaetomium globosum you could experience skin and nail infections. Occasional Chaetomium will produce mycotoxins, so it should be removed from any building promptly.

  1. Stachybotrys chartarum (black mold)

Probably the most dreaded mold in the United States, Stachybotrys chartarum also goes by the name “black mold.” This type of mold gets its colloquial name from the dark green to black color. It has a slimy texture, grow in moist and humid environments, and primarily grow on materials like wood, cardboard, paper, hay, and wicker.


Stachybotrys chartarum is dreaded because it is a highly toxic mold that produces mycotoxins. Symptoms of this mold include breathing problems, sinusitis, fatigue, and depression.



  1. Trichoderma

There are five different species of Trichoderma. All of them are white with green patches. The mold itself looks like wool balls clustered together. This type of mold is usually found on wet wallpaper and carpet.


Most of the five species of Trichoderma are non-harmful to humans. However, so may cause mild allergic reactions. Plus, it is one of the most damaging molds to structures, as it has an enzyme that destroys wood.

  1. Penicillium

In medicine and food production, Penicillin is an enormously helpful mold. But, in your home it can be harmful. This is one of the easiest molds to identify, since it has a blue-green color and velvet-like texture. Like all mold, Penicillin thrives in moist environments like water-damaged buildings.


If you are exposed to Penicillin you can have respiratory symptoms. If left untreated, it can also cause pulmonary inflammation and asthma, or even chronic sinusitis.

Cladosporium cladosporioides

Cladosporium cladosporioides

Chaetomium globosum

Chaetomium globosum

Stachybotrys chartarum



Trichoderma sp. (36433675342)


Penicillium unknown

Mold health concerns

The question you’re probably asking is, will mold hurt me or my family? The answer is a qualified yes. Some varieties of molds common to homes are dangerous. Some potentially harmful molds are Aspergillus fumigatus, Cladosporium cladosporioides, Chaetomium globosum, Trichoderma spp., and Stachybotrys chartarum.

Symptoms of potentially harmful molds can be mild to severe. Your reaction depends upon the type of mold you are exposed to and whether you have any allergies. Severe reactions may include difficulty breathing, fever, asthma attacks, and immunity problems. More mild symptoms are sneezing, coughing, and other allergic reaction signs.

But, just because you find mold in your house doesn’t mean you have to run screaming for the hills. Many mold varieties will not hurt you or cause allergic reactions in most people. Varieties that may be unsightly, but safe are Ulocladium botrytis, and Wallemia sebi.

People with extreme allergies or that are super sensitive may have mild reactions to these molds. But, the majority of the population will not have any problems. Keep in mind that mold can cause monetary as well as health damage, so you should have any mold removed even if it is of the harmless variety.

How to remove mold                     

Find Out what to use and how to clean up mold here

The process of removing mold is called remediation. This procedure is best left to the professionals. It can be quite complicated because the mold spores must be removed without causing further exposure to any humans.

Plus, to ensure that you won’t have mold problems again, professionals must remove all of the mold in your home. This can be a problem because of the many hard-to-reach places that mold can grow. In order to get rid of all of the mold in your home, professionals use special mold remediation equipment.

In addition to removing the mold from your home, the mold remediation professional is also responsible for repairing any damage that has occurred. This could be as simple as wallpapering again or as large a project as putting in a new wall.

Because of the complicated nature of mold remediation, you should contact a professional company. They will remove the mold and help to keep you and your family safe.