Molds are microscopic microorganisms that grow on many materials and are capable of breaking organic matter they use as food. They can be found wherever there are organic materials and moisture, which are the necessary ingredients for mold growth. Molds are found both indoors and outdoors, and in any area of the country and the world. Some are visible, some are not.


Except in structures where all of the incoming air is filtered and cleaned, there is never going to be a “mold-free” condition. Therefore, when checking a house for mold, the goal is to have the indoor mold condition equal to or lesser than the outdoor condition. Mold screening of the indoor and outdoor conditions determine if an indoor mold problem exists and what types of molds are growing indoors.

Mold spores generally enter a home on air currents, clothing, shoes and house pets. They thrive particularly well on cellulose materials such as wood, drywall, ceiling tiles and carpet. When a mold spore comes into contact with a suitable surface, it germinates and begins to grow. Each mold colony (mycelium) then produces millions of microscopic spores within a few days, and continues to grow as long as sufficient moisture and food is present. 


The health effects from mold exposure are very symptomatic, and vary from person to person. How the human system is affected by mold exposure is dependent upon what types of mold are growing and the condition of the person exposed to the mold.

Health effects attributed to mold exposure may be:
 Respiratory failure/asthma; Flu Symptoms/headaches; Nose bleeds/bleeding lungs; Dizziness; and   Learning disabilities. The more serious health effects attributed to mold are more commonly found in people who already have compromised systems. Most people are not noticeably affected by small levels of mold.


There are approximately 100,000 genera of mold species known today, with approximately 80 genera suspected of causing some kind of illness. Only a fraction of the 80 genera are considered toxic. Molds are organized into three groups according to human responses: Allergenic, pathogenic and toxigenic. Allergenic molds do not usually produce life-threatening health effects, and are most likely to affect those who are already allergic or asthmatic. The human system responses to allergenic molds tend to be relatively mild, typically producing only scratchy throats and rashes. Pathogenic molds usually produce some type of infection. They can cause serious health effects in persons with suppressed immune systems, although a normal, healthy individual can probably resist infection by these organisms regardless of dose. In some cases, high exposure may cause hypersensitivity pneumonitis (an acute response to exposure to an organism). Some molds produce mycotoxins that can cause serious health effects in almost anybody. These agents have toxic effects ranging from short-term irritation to immunosuppression and possibly cancer. Therefore, when toxigenic molds are found further evaluation is recommended.


Airborne spores will eventually land and settle on a surface. Spores may or may not germinate immediately, but they are built for survival. The spores may lie dormant, waiting for the right condition for growth. The following conditions may be conducive for mold growth:


Moisture. When looking for the source of a mold growth, look for moisture. Spores can survive, germinate and reproduce in as little as 65% equilibrium relative humidity (water activity of 0.65).

Food Source. Food sources for mold are practically any organic materials, such as wood, drywall, insulation, and natural fibers, which may have been exposed to moisture.

Raw Materials
. Even before a new home is built, the raw materials used can collect moisture and mold, especially if exposed to the ambient.

Minimal Air Circulation. An example of minimal air circulation is two pieces of wood coming together, such as where a floor joist meets at the band joist.

HVAC systems. HVAC systems and ductwork often contains porous materials, moisture, and dirt.

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