Mold is a type of fungi. They are part of some very first forms of life on earth. There are about 100K to 300K types of mold species but, only a few grow inside houses. So, relax and don’t be afraid of the numbers. Let’s look in to 12 most common molds in houses and where to find them.
There are about 100 different species of Acremonium. It was known as Cephalosporium before. This mold grows in areas with constant wetness. To be more precise, it is more prevalent on cellulose based materials which are wet or damp for a long time.
It can develop on damp drywall and Air Conditioning Piping. The insulation used in heating and cooling systems is more prone to this kind of mold infection.
Acremonium grows and spreads slowly compared to other types of mold. It is found in various colors like Grey, Pink, White and Orange. It has a powdery texture and difficult to find.
Acremonium may cause some worst health issues and must be removed right away. The weird fact about this mold is that it is helpful as well as harmful. Arcemoinum is used to make the antibiotic, Cephalosporins.
There are over 40 different species of Alternaria mold. This mold grows outdoors in dry windy conditions. The presence of this mold can be seen on carpets, upholstery and bedding. It can also be found in damp areas like shower and sink.
Alternaria has a complex structure. In other words, the morphology is unique compared to many other fungi. It is more commonly found when there is some other type of mold is also present.
Some advanced research confirmed higher level of Alternaria in houses using dehumidifier. The presence of cats and dogs was also found associated with higher level of Alternaria. Some other factors are, old building structure, less frequent cleaning and indoor smoking.
Alternaria is an allergenic mold causing respiratory allergies and severe asthma.
There are about 200 different species of Aspergillus mold. A very small number of them affect human health. Aspergillus fumigatus is the species that affects humans often. Aspergillus may infect the respiratory system and cause lung diseases.
This mold can be found both indoors and outdoors. Indoors, it grows on drywall, paint and wallpaper. Also, on plotted plant soil, rotted wood, mattress dust and carpet. It is also found on air conditioner piping and humidifier containers. Moreover, a significant amount of Aspergillus floats in indoor air which you can’t even see!
Aspergillus appears in many colors, but the most common colors are yellow, green and white.
There are about 15 different species of this mold. Aureobasidium is very common indoors. And cultivates on wet materials, wet wood, basements and windowsills. Aureobasidium Pullulans is well known for its commercial and industrial uses. It is useful in food, pharma, agriculture, as an adhesive and many more.
Aureobasidium is pink or black colored. There is no set environment for this mold as a favored one. As it cultivates anywhere in the world with any kind of climate. It can grow in cold Arctic or hot Africa.
Some species of this mold are categorized as irritants and allergens. It may affect your pulmonary system (breathing and lungs). And it may also infect your skin and cause dermatitis.
This one is 2nd or 3rd most common mold found in water damaged buildings. There are close to 90 different species of Chaetomium. It is mostly white or grey in color.
This type of mold is cellulolytic in nature and found in cellulosic materials. For example, paper, cotton cloth, drywall, wallpaper and wood. Chaetomium produces cellulase enzyme. This enzyme eats up the materials having cellulose.
Chaetomium has a direct relation with excessive dampness. In other words, if you have signs of Chaetomium in your house, then it is a sign of chronic moisture issue. One of the most common species found indoors is Chaetomium globosum. Sometimes, it grows in combination of other molds.
Chaetomium globosum creates a very high number of mycotoxins. It can prove fatal in case of people with weak immune system. The health impacts on humans by Chaetomium are not very clear but it is indeed harmful if found indoors.
Cladosporium has a very slow growth in winter but faster in spring and summer. This mold can grow in cold conditions. It can also grow inside the refrigerator and spoil the food. It can grow at low temperature as low as -10 degree Celsius.
Cladosporium is usually black, brown or green colored and there are over 40 species of this type. It is widespread outdoors as well it can grow on anything indoors. Most of the times, on food and organic materials. Some studies have found this mold on surface of the glass fibers inside water pipes.
It is non-toxic for human body but, it is classified under allergenic mold. Because, it can affect weak immune people with allergies.
Fusarium was once in news for its use or proposed use as a biological weapon! Because it has an ability to grow and expand wildly. Especially, damaging crops and causing a loss of multi million dollars. Well, let’s stick to our domestic war with this mold while you find it inside your house.
Fusarium is usually pink, white, brown or red in color with a cotton like appearance. The occurrence of Fusarium is associated with water leakage or seepage issues. Any water damaged building materials are at risk of getting affected by Fusarium.
This mold can is in the list of most dangerous mold types that may harm human health. Because, it can cause serious critical health issues along with allergies. It can enter your blood streams and nerves to create serious infections.
Like Cladosporium mold, Fusarium can also grow in minus temperatures.
About 40 to 50 different species of Mucor mold has been named so far. And 4 or 5 species of them are really of a concern for us in our houses. They are in white or beige color and resemble a grey look at maturity.
Same as many other molds, it grows in soil or dead plants. After maturity, the spores will enter indoors with help of wind or other medium.
It can easily grow at spots with constant dampness or water leaks. Damp or dusty carpet, water damaged basement are some favorite spots of this mold. In addition, leaky HVAC systems are also prone to its growth. The bread and some other foods in your kitchen are another favorite place for Mucor!
Mucor is one of the very fast growing and dangerous mold. It can infect human respiratory system and cause severe damages. Most Mucor species have a limitation that they can’t infect humans and warm- blooded animals. As it can not sustain in temperatures close to 37-degree Celsius.
In rare cases, prolonged exposure can cause severe health issues. Mucor mold can cause Mucormycosis which literally eats up tissues. It is sometimes called flesh eating mold especially after the case of Mark Tatum “The man without a face”. Mark had a heavy mold infection in his house.
So, do not ignore Mucor or any other mold signs. Call a professional mold removal contractor right away, if you spot it inside your house.
Rather than being fearful, we should be more thankful to this mold as it saved millions of lives!
In the year 1928-29, Sir Alexander Fleming discovered a special “mould juice”. This “mould juice” was from Penicillium mold with a strong ability to kill bacteria. This led to development of first ever antibiotic Penicillin.
The other good use of one of the Penicillium species is cheese production. Some special varieties of cheese are ripened with help of this mold.
Afterall, it is a mold and there is (obviously!) a bad side of it! Especially when found indoors. Most of the time, it shows up after flooding in your house. In cases of water damage, it grows in combination with some other toxic molds. Like Aspergillus, Cladosporium and Paecilomyces.
Penicillium causes blue or green spots on fruits and vegetables. Some water-based glue used for wallpaper are favorite food for this mold. The other areas are damp drywall and wet floors. Also, leaky structures with plumbing issues or external water seepage.
There are about 200 different species of Penicillium. About 20 are commonly found indoors. A few out of the 20 may produce mycotoxins which can harm our health. Penicillium chrysogenum, is one of the common species indoors. And the same species helps to make Penicillin!
It can cause allergies and can hit the weak immune people more often. Penicillium mold also attacks HIV infected patients as an easy target.
This one is the most talked about mold out of the 12 most common molds in houses we are discussing here. And known as black mold. As it can easily find its habitat inside damp buildings. And the health impacts could be little severe.
The scientific name of black mold is Stachybotrys chartarum. Also known as Stachybotrys atra. The building materials rich in cellulose combined with excessive dampness, cause rapid growth of this mold. It is black or dark green in color. It may start growing with signs of yellow stains on walls in the early stages.
Black mold can grow on face of drywall and back of drywall in leaky basements. Also, behind kitchen counters, sink cabinetry, carpet and carpet sub floors.
This mold could be one of the major factors causing Sick Building Syndrome (SBS). Sick Building Syndrome is something that gives you a weird feeling for no clear cause.
Occupants in the buildings with poor indoor air quality usually complain about headache. Also, about fatigue, skin and eye irritations. And these symptoms could be related to SBS.
Poor ventilation with high humidity is favorite site conditions for molds like S. chartarum. These conditions add up to Sick Building Syndrome effects.
Keep in mind that some other mold types also resemble same black color. But, Stachybotrys chartarum as black mold is most talked about in recent years. Due to its widespread presence and association to severe health issues.
Experts suggest that Stachybotrys chartarum can produce many varieties of mycotoxins. And constant research continues to study health impacts of different molds, including Stachybotrys.
The species Trichoderma viride was the only known species for several years. Recently some more are classified under the same type. Trichoderma is one of those special kinds who can kill some other fungi. So, it is very useful in agriculture to eradicate some plant pathogens.
Indoors, like many other molds, Trichoderma may develop on cellulose rich materials. Especially on drywall, wood, carpet and some fabrics. This is one of the fastest growing molds. And it may spread through your HVAC system to entire house. White or green spots on walls could be the sign for the growth of Trichoderma.
Some species are resistant to fungicides and difficult to detect until very late. People with weak immune system and HIV infection are vulnerable to this mold’s bad effects on body.
On the other end, Trichoderma is very useful in production of antibiotics and immunosuppressant. Antibiotics kills other fungi and bacteria. While immunosuppressant is useful in organ transplant to avoid rejection.
Whenever this mold is seen inside house, it is a sign of heavy water damage or constant leakages. Ulocladium is usually greenish brown or black in color. Due to heavy moisture needs for its growth, it usually grows in wet basements and bathrooms.
Using a water-based glue for wallpaper is another factor inviting the mold growth. Recently, most manufacturers have started supplying materials keeping in mind microbial control.
Ulocladium and Alternaria mold are closely connected and both may cause allergic reactions.
Alternaria species are among the most abundant fungi. Alternaria can cause allergic reactions. Headache, coughing, sneezing, runny nose, itching are common symptoms of allergies.
To completely remove Ulocladium, first treat the water leakage and humidity on priority.
Hope the above details on 12 most common molds in houses will help you understand a little more about molds found indoors. Also, to realize that mold removal is not a DIY thing and you need a licensed professional to help you.
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This article is more on awareness for mold removal. We are not claiming to be expert mold advisors. Any information on health impacts of mold must not mean a health advice from us.
Sources and acknowledgements:
This article is an attempt to make the understanding of mold- a little simpler and easier. We also acknowledge the use of some information from following sources. And we are very thankful to those publishers.
1. NCBI: National Center for Biotechnology Information : According to NCBI, someauthors directly relate fungal contaminated indoor environments to illness. But, a close examination by experts reveal a confusing picture not fully confirming it!
2. MBL: Mold & Bacteria Consulting Laboratories.
3. Global Indoor Health Network, Inc.
4. WHO Guideline.
5. Residential Indoor Air Quality Guideline: Moulds (Government of Canada / Canadian Mold Guideline)