What is Mold?

Information about the science of mold and how it grows in an indoor environment

Mold is also known as fungi, which is a diverse group of organisms that include mold and mildew, mushrooms, yeast, smuts and rusts. The primary objective of fungi in nature is to decompose organic matter. It is what we rely on to decompose the remains of dead plants and animals in nature.

Mold is commonly found in the air. The single units of mold that become airborne are called spores. Higher concentrations of spores are often found near large sources of dead plant or animal life. While mold is common in nature, and it can sometimes flow into the indoor air of a building, it is not common or natural to find large concentrations of mold in an indoor environment. It is also uncommon to find concentrations of toxic mold in an indoor environment.

Toxic mold isn’t toxic in itself. It is the byproduct released by these types of mold that is considered toxic or harmful to humans and animals. This harmful byproduct is known as a mycotoxin and can become airborne in spore form.

Mold gets inside of a building either through spores that travel inside through the air or by being brought into a building via an object that has been in contact with a mold source. By air is the most common. The transfer of mold spores from an object is usually from a pet or plant. A pet coming into contact with mold in nature and a plant being brought in with mold on its structure or in its soil.

In order for mold to begin growing and forming colonies, it requires organic material and moisture. Since nearly all building material contain organic material, and organic material can also be found in several interior places in the form of small particles of dead human skin and other matter, the organic food source is covered. In fact, because of interior dust being composed or mostly dead organic matter, mold has the potential to grow anywhere within a building. This, if it has an adequate moisture source.

The moisture needed for growth can come from a variety of sources, including:

  • Excess humidity
  • Leaking pipe within a wall or floor
  • Leak from a fixture, such as sink, toilet, bath or shower
  • Moisture from a water damage or sewer backup situation
  • Condensation near a window
  • Roof leak
  • Damp crawlspace or concrete slab caused by improper exterior drainage
  • Several other possible sources

Once mold has found adequate moisture, it begins to grow. While growth depends on environmental factors, mold can thrive in a variety of conditions and temperatures. In fact, mold can grow in temperatures as cold as 36 degrees and as warm as 100 degrees Fahrenheit. The ideal temperature for faster growth, however, is between 65-84 degrees Fahrenheit. This is why mold is often noticed more frequently after the weather warms-up versus during cold winter months.

There are over 100,000 different species of mold that have been identified by scientists. Out of all of those identified, a much narrower number have been identified as common types that exist in nature around the United States. Many of these species have been placed into classes or families. The mold species are classed together because they are so similar in appearance, behavior, and genetics, that there are few ways to tell them apart. These classes of mold are what people refer to in the reporting of mold during inspections.

Out of the common classifications of mold found within nature, they can each vary greatly in color, shape, and other characteristics. This is one of the reasons why a visual-only mold inspection cannot work. In order to determine the type of mold present (and if it’s even mold at all), a sample of the mold must be taken for laboratory analysis to find out what it is.

A popular term used to describe harmful mold is “black mold”. While it is true that there are types of mold that are harmful to humans that are black in color, there are also several types that can be harmful that are green, brown and orange in color. On the same note, there are also other types of mold that are black in appearance that aren’t considered toxic to humans.

Assuming mold has all of the right resources it needs, it can grow; and grow; releasing spores in the air. The amount of mold spores in the air is known as the concentration. When higher concentrations of spores are present, or when any concentration of toxic mold is present, in the breathable air of the property, the environment is considered to be a health risk to those occupants. At this point, immediate action is recommended to remediate any mold concerns.