Uploaded July 2025 | Updated September 2026, 1 week ago
Mold can be found both in the indoor and outdoor environment. It is a natural part of the environment and plays an important role in breaking down and digesting organic material. However, exposure to elevated levels of mold in the air people breathe can cause issues.
There are many different types of mold, with some 1.5 million species estimated to exist, according to the National Toxicology Program. Mold multiplies by producing microscopic spores. These spores are so small they easily float through the air and can be carried for great distances.
The U.S. Environmental Protection Agency (EPA) states that mold is usually not a problem indoors unless mold spores land on a wet or damp area - allowing them to begin to grow. Common sources of indoor moisture include roof leaks, condensation due to high humidity or cold spots in a building, leaks from plumbing fixtures, humidification systems, sprinkler systems, and floods.
As mold grows indoors, it can cause unpleasant odors and cosmetic damage, such as stains. Left unchecked, mold can also cause serious damage to a home or building. It can destroy belongings and furniture, and it can rot wood – even resulting in structural damage.
The potential human health effects of exposure to elevated levels of mold are also a concern. Allergic reactions to mold are common and can be immediate or delayed. They include hay fever-like symptoms such as headache, sneezing, runny nose, red eyes, and skin rash. Mold can even cause asthma attacks in some asthmatics. Mold can also be an irritant, affecting the eyes, skin, nose, throat, and lungs. Some types of mold are known to cause infections in people with weakened immune systems. Mycotoxins are yet another health concern as some types of mold can produce these toxic byproducts.
These are just a few of the many things to know about mold growth in the built environment. To learn more about this or other indoor air quality, industrial hygiene, environmental, health, or safety issues, please visit the websites shown below.
Clark Seif Clark csceng.com
EMSL Analytical, Inc. emsl.com
LA Testing latesting.com
Zimmetry Environmental zimmetry.com
Healthy Indoors Magazine healthyindoors.com
Mold can be found both in the indoor and outdoor environment. It is a natural part of the environment and plays an important role in breaking down and digesting organic material. However, exposure to elevated levels of mold in the air people breathe can cause issues.
There are many different types of mold, with some 1.5 million species estimated to exist, according to the National Toxicology Program. Mold multiplies by producing microscopic spores. These spores are so small they easily float through the air and can be carried for great distances.
The U.S. Environmental Protection Agency (EPA) states that mold is usually not a problem indoors unless mold spores land on a wet or damp area - allowing them to begin to grow. Common sources of indoor moisture include roof leaks, condensation due to high humidity or cold spots in a building, leaks from plumbing fixtures, humidification systems, sprinkler systems, and floods.
As mold grows indoors, it can cause unpleasant odors and cosmetic damage, such as stains. Left unchecked, mold can also cause serious damage to a home or building. It can destroy belongings and furniture, and it can rot wood – even resulting in structural damage.
The potential human health effects of exposure to elevated levels of mold are also a concern. Allergic reactions to mold are common and can be immediate or delayed. They include hay fever-like symptoms such as headache, sneezing, runny nose, red eyes, and skin rash. Mold can even cause asthma attacks in some asthmatics. Mold can also be an irritant, affecting the eyes, skin, nose, throat, and lungs. Some types of mold are known to cause infections in people with weakened immune systems. Mycotoxins are yet another health concern as some types of mold can produce these toxic byproducts.
These are just a few of the many things to know about mold growth in the built environment. To learn more about this or other indoor air quality, industrial hygiene, environmental, health, or safety issues, please visit the websites shown below.
Clark Seif Clark csceng.com
EMSL Analytical, Inc. emsl.com
LA Testing latesting.com
Zimmetry Environmental zimmetry.com
Healthy Indoors Magazine healthyindoors.com
