Common Indoor Molds


Photo by Anne Elliott

What Types Are In Your Home?

Mold can grow anywhere there is moisture, and both indoor and outdoor molds can cause health problems for humans.  It exists in many types, far too many to know them all, and in many colors.  Most people are familiar with the terminology, black mold or green mold.  Black just happens to be the color we mostly notice, but all molds can be toxic to humans.  Of the many hundreds of species, there are only a small few that are not considered harmful to humans. Here we discuss some of the most common and deadliest mold species.

According to the Centers for Disease Control and Prevention (CDC), the most common indoor molds are Cladosporium, Penicillium, Aspergillus, and Alternaria.  Stachybotrys chartarum is another species about which we should be concerned, and while not necessarily a common mold species, it is also not a rare one and found in many homes or offices.


The CDC classifies this mold as a pathogenic fungi found in the environment.  It can be found both indoors and outdoors.  Indoors, it is most commonly found in the air and anywhere moisture resides, such as carpet, wallpaper, paneling and ceiling tiles.  While the mold rarely causes illness in humans, it is responsible for infections and allergies.  It is considered toxic.


Yes, this is a mold.  This is the one you find on your fruit and bread when it is no longer edible, and can be found anywhere there is dead plant material.  It can be responsible for asthma and even kidney and liver damage.  Amazingly, however, this fungi is also useful in the manufacture of antibiotics, organic acids and cheese. With this mold, it is all about the application. Penicillium is not healthful in your home.


There are almost 200 species of Aspergillus, but only about 40 are known to be responsible for infections in humans.  Surprisingly, this mold is found in the air we breathe, and most of us breathe it in with no adverse reactions.  However, for those with weakened immune systems, this fungi is a real problem.  This one is also found on spoiled food like Penicillium. It can also be found in air conditioning vents or on damp surfaces.

Aspergillus causes a fungal disease known as aspergillosis, of which there are several types.  It is important to note that aspergillosis is not a reportable infection in the United States, making it difficult to speculate on exactly how common it is.  According to the CDC, more often it is mild, allergic forms of aspergillosis that we observe.


Alternaria, commonly found outdoors on diverse types of vegetation, is also one of the most widespread causes of indoor allergic infections. This particular pathogenic fungi is one of those most commonly responsible for asthma and its perseverance. A study found that over 90% of dust samples taken from homes in various regions contained the fungi.  The good news is that regular dust removal can help alleviate the issues associated with this mold.


Stachybotrys chartarum is a greenish black mold that grows in materials that are high in cellulose.  It is commonly found indoors, and especially in building materials that have been water compromised.  This mold is known to cause toxic inflammatory infections in infants and office and warehouse workers.

It is not always necessary to determine the exact type of mold, but to determine its existence in your home or workplace.  No matter what type of mold you encounter in your home, it should be treated as serious.



Leave A Reply