Mold Facts

What is mold?

Molds are forms of fungi found all year round both indoors and outdoors. Outdoors, molds live in the soil, on plants, and on dead or decaying matter. Another common term for mold is mildew. Mold growth is encouraged by warm and humid conditions, although it can grow during cold weather. There are thousands of species of mold and they can be any color. Many times, mold can be detected by a “musty odor”. Most fungi, including molds, produce microscopic cells called “spores” that spread easily through the air. Live spores act like seeds, forming new mold growths (colonies) with the right conditions. All of us are exposed to fungal spores daily in the air we breathe.

What is “black mold”?

The news media often refer to “Black Mold” or “Toxic Black Mold.” It is usually associated with Stachybotrys Chartarum, a type of greenish-black mold commonly associated with heavy water damage. Not all molds that appear black are Stachybotrys. The known health effects from exposure to Stachybotrys are similar to other common molds, but have been inconclusively associated with more severe health effects in some people.

What are Microbial Volatile Organic Compounds (MVOCs)?

Chemicals produced by fungi as a result of their metabolism. Some of these chemicals are responsible for the characteristics moldy, musty, or earthy smell of fungi, whether mushrooms or molds. Some MVOCs are considered offensive or annoying. Specific MVOCs are thought to be characteristic of wood rot and mold growth on building materials. The human nose is very sensitive to mold odors, sometimes more so than current analytical instruments.

How does mold get into a house or building?

Most, if not all, of the mold found indoors comes from outdoor sources. It needs moisture to grow and becomes a problem only where there is water damage, high humidity, or dampness. Common sources of indoor moisture that cause mold problems include flooding, toilet overflows, roof and plumbing leaks, damp basements or crawl spaces, or any moisture condensation on cold surfaces. Bathroom showers and steam from cooking may also create problems if the areas are not well ventilated.

What is hidden mold?

Visible mold growth on building structures that is not easily seen. For example: above drop ceilings, within a wall cavity (the space between the inner and outer structure of a wall), inside air handlers, or within the ducting of a ventilation system. Visible mold within a ventilation duct is in immediate contact with the occupied space. Spores released from such growths are affected by air movement and relative humidity. Spores of mold growth in wall cavities are released by air exchange between the wall cavity and occupied space. The rate of spore movement between such spaces is typically slow. Volatile gases produced by visible mold growth in wall cavities are also known to occur and migrate to occupied spaces even through air barriers.

How can I prevent mold growth?

Controlling excess moisture is the key to preventing mold and stopping indoor mold growth. Keeping susceptible areas in the home clean and dry is very important. Ventilate or use exhaust fans (vented to the outdoors) to remove moisture where it accumulates, particularly in bathrooms, kitchens and laundry areas. Clothes dryers should be vented to the exterior. Repair water leaks promptly, and either dry out and clean or replace water damaged materials. Materials that stay wet for more than 48 hours are likely to produce mold growth. Lowering humidity indoors helps prevent condensation problems. To lower humidity during humid weather, use air conditioners and dehumidifiers. Proper exterior wall insulation helps prevent condensation from forming inside during cold weather.

Why should I be concerned about mold?

Small amounts of mold growth in workplaces or homes (such as mildew on a shower curtain) are not a major concern. But no mold should be allowed to grow and multiply indoors. Large quantities of mold growth may cause nuisance odors and health problems for some people. In addition, mold can damage building materials, finishes, and furnishings and, in some cases, structural damage to wood.

How do molds affect people?

Most people have no reaction when exposed to mold. Allergic reactions, similar to common pollen or animal allergies, and irritation are the most common health effects for individuals sensitive to molds. Flu-like symptoms and skin rash may occur. Molds also aggravate asthma. In rare cases, fungal infections from buildings-associated molds may occur in people with serious immune disease. Most symptoms are temporary and eliminated by correcting the mold problem.

Common Health Effects and Symptoms Associated with Mold Exposure

When moisture problems occur and mold growth results, building occupants may begin to report odors and a variety of health problems, such as headaches, breathing difficulties, skin irritation, allergic reactions, and aggravation of asthma symptoms; all of these symptoms could potentially be associated with mold exposure.


All molds have the potential to cause health effects. Molds produce allergens, irritants, and in some cases, toxins that may cause reactions in humans. The types and severity of symptoms depend, in part and their existing sensitivities or allergies.

Specific reactions to mold growth can include the following:

Allergic Reactions

Inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals. Allergic reactions to mold are common. These reactions can be immediate or delayed. Allergic responses include hay fever-type symptoms, such as sneezing, runny nose, red eyes, and skin rash (dermatitis). Mold spores and fragments can produce allergic reactions in sensitive individuals regardless of whether the mold is dead or alive. Repeated or single exposure to mold or mold spores may cause previously non-sensitive individuals to become sensitive. Repeated exposure has the potential to increase sensitivity.



Molds can trigger asthma attacks in persons who are allergic (sensitized) to molds. The irritants produced by molds may also worsen asthma in non-allergic (non-sensitized) people.

Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis may develop following either short-term (acute) or long-term (chronic) exposure to molds. The disease resembles bacterial pneumonia and is uncommon.

Irritant Effects

Mold exposure can cause irritation of the eyes, skin, nose, throat, and lungs and sometimes can create a burning sensation in these areas.

Opportunistic Infections

People with weakened immune systems (i.e., immune-compromised or immune suppressed individuals) may be more vulnerable to infections by molds (as well as more vulnerable than healthy persons to mold toxins). Aspergillus Fumigatus, for example, has been known to infect the lungs of the immune-compromised individuals. These individuals inhale mold spores which then start growing in their lungs. Trichoderma has also been known to infect immune-compromised children.

Who is affected by exposure to mold?

There is a wide variability in how people are affected by mold exposure. People who may be affected more severely and quickly than others include:

  • Infants and children
  • Elderly people
  • Pregnant women
  • Individuals with respiratory conditions or allergies and asthma
  • Persons with weakened immune systems (for example, chemotherapy patients, organ or bone marrow transplant recipients, and people with HIV infections or autoimmune diseases)

Those with special health concerns should consult their doctor if they are concerned about mold exposure. Symptoms that may seem to occur from mold exposure may be due to other causes, such as bacterial or viral infections or other allergies.

Who needs a mold inspection?

Have a new baby or a loved one with frequent headaches, asthma, depression or other health concerns that doctors have been unable to diagnose the cause and that seems to be worse while you’re in your home?

Has there been a recent “water intrusion” such as a toilet overflow, plumbing leak, roof leak, window leak, flood or major water loss that was not completely dried within 24 hours? Are there signs of water staining or water damage on a wall, floor or ceiling? Is there a “musty odor” anywhere in the house, basement or sub-area? Does the basement have organic materials such as wood, wallboard, carpeting or wallpaper?

Buying a new house and had a home inspection that revealed concerns about “mold” or you want to be sure the new home you’re buying is safe for you and your loved ones?

…………..Or you simply want peace of mind

Who do I call to deal with extensive mold growth in my home?

A professional experienced in mold evaluation and testing may need to be hired to address extensive mold growth in a building. It is important to correct large mold problems as soon as possible by first fixing the source of the moisture problem and removing the contaminated materials, then cleaning the surfaces, and finally drying the area completely. If you use outside contractors or professionals, make sure they have experience with mold assessment. Check their references, and have them follow industry standard recommendations and guidelines.

Beware of Mold Remediation Companies offering free or very low cost MOLD inspection and sampling or those that perform both services, when their primary business and expertise is in the remediation industry and not in Mold Testing & Assessment. Remember, they have a vested interest in extensive remediation of your property which can be very costly!

The IICRC S520 Reference Guide for Professional Mold Remediation (Chapter 10: Indoor Environmental Professionals and Assessments) Independence- It is preferable that the Indoor Environmental Professional be an unbiased resource. An Indoor Environmental Professional engaged to perform pre-remediation assessment or post-remediation verification should be independent of the mold remediator. In some jurisdictions, the law may require that the inspection and assessment function be performed by an individual or entity independent of the mold remediator.