Mold – Hype or Real Risk?

Increasingly, we are talking about specific kinds of mold, not just old mold. Is this a new problem or just one that our technology is now allowing us to detect more effectively?

Are we overreacting or should we be concerned? If we should be concerned, what products or actions are most effective? Unfortunately, there is not a simple answer. We do have better technology that allows us to understand and analyze more of the world around us. Some of the air quality issue is simply because we know more about it.

However, it is also true that we are building homes and buildings that are more vulnerable to conditions that promote the growth of mold. It is also true that mold is one of the most common causes of frequently reported respiratory problems. The following is intended to provide an overview of what we know about mold and what we can do about it. Before you take any action in your own home or building, however, you should consult a local specialist: a building inspection engineer.

The problem of mold is one that no building owner or manager can afford to ignore. Mold has been suggested as one possible factor in so-called Sick Building Syndrome. The unusual weather conditions in many parts of the United States in recent years have provided good conditions for the growth of toxigenic fungi and increased the potential for human exposure. Throughout the country, deaths of children from pulmonary hemosiderosis (bleeding lung disease) have been attributed to inhalation of toxins produced by the fungus Stachybotrys chartarum.

The U.S. Department of Housing and Urban Development awarded $3.1 million to the city of Cleveland to remediate mold and moisture problems in houses and apartments. Mold problems in the Martin County Courthouse in Florida apparently caused by a leaky EIFS (exterior insulation finish system) facade cost $26 million to remediate. The building cost $13 million to construct a few years earlier. An old school building in Canada, infested with toxigenic fungi, had to be burned. Mold is a problem.

What is mold?

The words mold and mildew are sometimes used interchangeably. If there is a difference in the two terms, it is that mildew generally refers to a fungus-caused discoloration of an underlying, porous material, whereas mold refers to a fungus growth on a porous, often rotting material. Essentially, mold is the growth produced by several types of fungi as they feed on organic matter. Mold typically reproduces asexually by means of airborne spores. These spores are always present in the air. There are thousands of types of fungi (mold).

Many fungi are helpful. Some good types of fungi are those used to produce Camembert and Roquefort cheeses. The wonder drug penicillin is a by-product of the fungus Penicillium notatum.

What does it need from us?

Like all living things, mold spores need certain conditions to reproduce and grow. Mold needs water, food, and the right temperature range. Mold grows better in a dark environment, and with an organic, porous material to grow on. Such material often provides a source of both food and water.

Unfortunately, buildings provide an almost ideal environment to support the growth of mold. The typical temperatures are right, and there are plenty of dark places and organic substances. Just add water, and you’ve created a perfect mold breeding ground.

Dry rot, a common condition in older homes, is bacterial activity similar to mold and needs the same combination of conditions for ideal growth. If you have dry rot, you probably have mold. The reverse is true as well.

Why should we be concerned?

Mold can feed on and destroy most of the organic materials found in buildings such as wood, paper, carpet, and glue. However, almost any surface can support the growth of mold. Although mold can be found anywhere, it typically grows in dark, moist places such as behind walls or in HVAC ducting.

Mold can cause harmful health effects in humans. Although the species Stachybotrys chartarum (sometimes referred to as stacky for short) has received most of the recent press, many other types of fungi are potentially harmful to humans as well. For this reason, Stachybotrys chartarum is not treated as a unique case.

One bit of good news: although Stachybotrys chartarum is considered one of the more hazardous forms of mold, its spores are wet and slimy. That makes it a bit easier to visually identify and much less likely to become airborne. Stachybotrys chartarum is usually transferred by contact with insects or rodents or by water.

Exposure to fungus can cause organic dust toxic syndrome (ODTS) or hypersensitivity pneumonitis (HP). ODTS may occur following a single exposure to high concentrations of dust contaminated by fungus, such as might be encountered during remediation or renovation work. The symptoms are flu-like. HP occurs as a result of prolonged exposure and can lead to permanent lung damage.

Exposure to fungus can also cause allergic reactions: typically a runny nose, sneezing, eye irritation, cough, or aggravation of asthma.

What should I look for?

Mold is not only a problem in itself but also a symptom of a water problem. The first step in any investigation for the presence of mold in buildings is to follow the water.

Look for evidence of high humidity, condensation, or visual evidence of water staining. Mold grows in dark, hidden places, such as behind walls, and may not always be visible. Other clues, such as musty odors or reported physical symptoms in occupants, should be noted.

How do I know if I have a mold problem?

If you see mold or evidence of moisture accumulation, test the suspect material. Testing, in order to identify the particular species of mold, can be performed by a number of laboratories. The EPA has recently developed a DNA-based testing procedure that dramatically reduces the time it takes to identify which of the 100 or so most common mold species may be present. Using this technology, tests that used to take days or weeks can now be performed in a matter of hours. Information on the EPA testing method is available at

Consultants and laboratories are listed under environmental laboratories or industrial hygienists in the yellow pages. Such firms can usually help with mitigation as well, should that be necessary.

How can I minimize the risk of mold?

Because mold likes the same temperature as humans, changing the ambient temperature as a method of control is not usually an option.

It is hard to eliminate the molds food source entirely, because it feeds on a wide range of materials commonly used in building construction and interior finishes. However, because mold can feed on dirt, cleanliness can go a long way toward control.

The easiest way to minimize mold growth is to eliminate sources of water. Moisture in a building can exist in two forms, as humidity and as free water. Moisture may come from inside the building through condensation, plumbing leaks, cooking, showers, or the HVAC system. Water may enter the building from the outside through leaks in the roof, the facade, or the basement. Water also may be introduced into the building through the use of wet building materials such as roofing materials, insulation, and drywall.

If you identify any of these sources of water or moisture, you should take immediate steps to eliminate them. This may require modifications to the structure, improved ventilation, improved environmental controls (HVAC), improved surface drainage, or any one of many other possibilities. You should consult a qualified building inspection engineer for advice.

How can I remediate an existing problem?

Any plan to remediate mold must first address solving the water problem. The source of the moisture must be identified and the condition rectified. Only then should the process of remediation begin.

Remediation consists of either cleaning the affected materials in place or the removal and replacement of these materials. The decision of whether to clean or replace is largely an economic one, based on the size of the areas affected, the ease of access, and whether or not the building components have been damaged by either mold or water.

If the buildings structural components are not damaged, small areas can usually be remediated by homeowners or maintenance staff. Trained contractors, however, should handle larger areas. Dealing with extensive areas of mold is like handling any other hazardous material and requires specific training. The New York City Department of Health publishes a useful guide titled Guidelines on Assessment and Remediation of Fungi in Indoor Environments. It is available on line at

Other ways of dealing with large infestations are being tested. At least one company treats moldy houses by enclosing them and raising the interior temperature in a controlled manner to about 160 degrees F. This effectively bakes the mold and kills it.

Most air cleaners (purifiers, ionizers, etc.) are not effective in dealing with a mold problem. At best, such equipment deals with the symptom rather than the cause.


For help with mold problems or suspected mold problems, the first step is to contact an engineer who is qualified to perform the diagnostics necessary to determine the root cause of the problem. Determining the cause of the problem, whether that is a leaky roof, facade issues, excess humidity, or a malfunctioning HVAC system, is often a complex process of detective work. There are often false leads, and inexperienced people often mistake effect for cause, leading to a misdiagnosis.

Breathing is essential to life. It is not an option. Breathing contaminated air can lead to respiratory irritations and, for some, can be life threatening. It is time well spent to inspect the buildings in which you live and work to determine if there are any suspect conditions that might lead to a mold infestation. If there are, testing, source identification, and remediation should follow quickly.