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Top 6 Types of Indoor Molds and How to Identify Them

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Species of Mold Found in Homes

Molds are fungi that can grow indoors and outdoors, often thriving in damp and humid environments. There are hundreds of species of mold, but these are common types of mold you can find in your homes:


Penicillium and Aspergillus are types of molds commonly found indoors. They typically appear as powdery or fluffy colonies in shades of blue, green, or white. These molds can grow on food, indoor surfaces like walls and ceilings, and in dust, making mold in walls a frequent issue.


Cladosporium is another mold found indoors commonly found in faulty HVAC systems. It typically grows on damp materials like wood, carpets, and fabrics. Cladosporium colonies are usually black or greenish-black in color and have a powdery texture.


Curvularia mold is in soil, plants, and sometimes indoors on damp surfaces such as carpets, mattresses, and window frames. It appears as dark-colored colonies with a velvety or cottony texture.


Chaetomium mold thrives in water-damaged areas such as attics and around leaky pipes. At first, it appears as a cotton-like texture and later develops into a grayish or brownish color. There are no universally established chaetomium safe levels like other molds.

Stachybotrys (Black Mold)

Often referred to as black mold, Stachybotrys thrives in areas with prolonged water damage, such as flooded buildings or areas with chronic leaks. It appears as a greenish-black mold with a slimy texture.


Memnoniella is closely related to Stachybotrys and is found in similar damp environments. It appears as dark-colored patches and can sometimes be mistaken for Stachybotrys.

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Why Are Mold Spore Level Important?

Mold spores in the air are microscopic particles produced by molds for reproduction and can become airborne, potentially causing health issues when inhaled. The term “spore level” specifically refers to the concentration of mold spores present in a specified volume of air. Most mold spore counts need to be lower indoors compared to outdoors. This is crucial because certain types of molds, such as Stachybotrys and Chaetomium, should not be present in the house at all. Even a single spore of Stachybotrys indoors is considered unacceptable due to its potential health risks.

Mold spores can thrive and spread more easily in indoor environments, which are often more humid and enclosed than outdoors. This is why indoor air quality guidelines are stricter. When assessing mold spore levels, don’t just rely on specific numbers. For example, if there are 10 spores of Penicillium/Aspergillus outdoors, having 400 spores indoors is not safe. The indoor level should be below the outdoor baseline to ensure safety.

this is a smaple of the amount of mold spores in the air after a mold testing

How to Calculate Spore Levels

Spore levels are typically measured through air sampling methods by a mold inspector in Houston, this is where air is collected and analyzed for mold spores per cubic meter or per square foot. The calculation involves determining the concentration of spores based on the volume of air sampled and comparing it to established guidelines for indoor air quality.

The EPA does not establish specific “EPA acceptable mold levels“. However, according to the American Conference of Governmental (ACGIH), there should be fewer than 1,000 mold spores per cubic meter of air in a day for people who aren’t sensitive to mold.

Understanding the different types of mold and how many spores they produce can help homeowners in Houston like you catch mold problems early. If you think there might be mold in your Houston home, it’s a good idea to contact mold experts in Houston. At Anderson Restoration, we’re specialists in mold removal. We can find and safely get rid of mold in your home.

Frequently Asked Questions:

How long can mold spores live?

Mold spores can stay inactive for a long time until the conditions are right for them to grow, which depends on the type of mold and the environment.

What do mold spores look like?

Mold spores are tiny and look different depending on the type. They’re usually round or oval-shaped and can feel smooth or rough under a microscope. They usually appear fuzzy, with color in black, green, greenish-yellow, orange & brown.

How big are mold spores?

Sizes of Mold spores are very small, ranging from 1 to 100 microns in size, so they’re invisible to the naked eye. This small size helps them float in the air and enter our lungs when we breathe.

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