- How does mold grow?
- How does mold get inside?
- How does mold spread?
- Can you see airborne mold spores
- Are there harmful and non-harmful molds?
- Does mold affect everyone the same way?
- How much mold exposure is harmful?
- Can "tighter" building construction promote mold development?
- Do new building materials (e.g. drywall or paper faced gypsum board) promote mold growth?
- Are there reliable tests to indicate the presence of mold?
- Is sampling required with every inspection?
- If mold is present, what's the best way to get rid of it?
- Is it possible to completely eleminate mold from the inside of a home or office building?
- Should I use bleach to get rid of mold?
- How do I know when the mold clean up is finished?
Mold requires nutrients, water, oxygen and favorable temperatures to grow. These nutrients are present in dead organic materials such as wood, paper or fabrics; from wet construction materials including wood, concrete, drywall, carpet or wallpaper; and from some synthetic products such as paints and adhesives.
Most often mold develops as the result of water intrusion from a flood, leaky pipe, or condensation. Unless water intrusions are dealt with within 48 hours of occurrence, ensuing mold issues are almost certain. The problem is, most small plumbing leaks and condensation issues go undetected until mold becomes a problem. The second most common way mold enters buildings is through the air or on people, animals and objects that are brought into the building.
Surface molds spread by eating the building materials they come in contact with. When surface molds are disturbed they produce mold spores, which become airborne. Airborne mold spores are (similar to seeds), they reproduce more spores. Another requirement for mold to grow is moisture, although some mold species can obtain that moisture from moist air when the relative humidity is above 70%.
Not with the naked eye. 250,000 spores can fit on the head of a pin. They are so light they will stay suspended in the air for 8 hours in a room with zero air movement.
There are more than 100,000 types of mold. Many cause infection in people of good health, while other molds cause infections only in people with compromised immune systems. Most people tolerate exposure to moderate levels of many different molds without any apparent adverse health effects, while others may have severe allergic reactions to the slightest amounts. Some molds produce powerful chemicals called "mycotoxins" that can cause illness in animals and sometimes people. Scientific knowledge about the health effects of these toxins on people is quite limited.
Of course not. Some individuals have a genetic makeup that puts them at risk for developing allergies to mold. People who have an allergy to mold, especially if they also have asthma, can become ill from exposure to a small amount of mold. Those most susceptible to mold-borne illness are infants with under developed immune systems, elderly with weakened immune systems. Anyone who suffers from respiratory infections such as pneumonia, bronchitis, etc., and people who undergo harsh medical treatments such as chemotherapy also have a higher susceptibility to mold-related health problems.
How to measure or estimate "exposure" levels to mold is difficult. Exposure means the amount of mold that gets into a person, usually by breathing, but also by eating or absorption through the skin. For example, a building may have a lot of mold in the walls but very little of that mold is getting into the air stream. In that case, the people working or living in that building would have little mold exposure. Even though the building itself is deteriorating, it does not mean that it is caused by mold. Remember: mold develops as the result of water intrusion from a flood, leaky pipe, or condensation. Unless water intrusions are dealt with within 48 hours of occurrence, ensuing mold issues are almost certain.
Tight construction combined with some poor choices in design, building materials or operations can increase the probability of mold growth. What do we mean? The tighter the building construction the less air exchange there is between the inside air and the outside air. Whatever gets into the inside air stays there longer than it would in a house with loose construction. Moisture that gets into the air from activities such as cooking, bathing and even breathing will remain in a tight house longer than it would in a loose house. That's why exhaust fans should be installed in bathrooms and kitchens and vented to the outside. Clothes dryers should also be vented to the outside.
Tight construction permits control of the air exchange between the inside and the outside and can prevent the deposition of moisture in walls and roofs. Controlling moisture, including indoor relative humidity is the key to preventing mold growth. Tight building construction when combined with source control of moisture (exhaust fans) and controlled ventilation (intentional introduction of outside air) reduces the probability of mold growth in a building. Controlled ventilation can be provided by a duct that brings outside air to the return side of the air handler of a forced air system. A timing device or fan cycler can be programmed to have the air handler turn on for a specified number of minutes each hour even when there is no call for heating or cooling.
Do new building materials (e.g. drywall or paper faced gypsum board) promote mold growth?
Mold needs water, a nutrient source, oxygen and favorable temperature to grow. Many species of mold love paper faced gypsum board. Why? Making paper involves the mechanical and chemical processing of wood. Paper is largely pre-digested so it is easy for mold to get nutrients from the paper. But unless there is enough moisture present mold can't grow on the paper. If paper faced gypsum board is kept dry, it can be used and still not have mold. This material is kept dry by controlling the interior relative humidity, keeping rain from entering roofs and walls, and NOT using paper faced gypsum in areas that are likely to get wet. This means no paper faced gypsum board in shower and tub areas. Cement board, mortar or non-paper faced gypsum can safely be used in these damp areas because these products do not contain nutrients to support mold growth.
- Eyes & Noses
If black or green discoloration is noticed and is in a location that is damp or had been damp, it is almost certainly mold. If a building smells musty, there probably is mold somewhere.
- Sample Testing:
Typically, mold testing is done either by extracting a sample from a suspect surface, or by extracting samples of the air. Both methods are accurate when analysis is preformed properly by a qualified lab.
It depends what the objective is. If the objective is simply to locate mold and identify its source, the answer is no. Once the source of mold is identified, air sampling does not provide additional meaningful information. Conversely, if the objective is to determine the types and/or amounts of mold present, the answer is yes. Air sampling provides a wealth of information and is the only reliable way to get a “snapshot” of the indoor air quality at the time the testing occurred.
The answer depends on how much mold is present and where it is located. If the mold is on furnishings or boxes simply discard the materials. It is smart to seal the mold material in heavy plastic to protect the people who handle it in transit and prevent spreading large amounts of the mold into the building as you carry the material out of it.
If the mold is on a hard surface but occupies less than 10 square feet, wash the area with an anti-fungal mildewcide (scrubbing with a brush may be necessary), then dry the area with commercial grade dehumidifiers before repainting. If you have asthma, severe allergies and a weaken immune system get someone else to do the clean up. In all situations, wear protective gear including rubber gloves, a respirator and face shield.
Larger areas greater than 10 square feet should be cleaned by a mold remediation company. Correct the source of the water or the mold is likely to recur.
To keep a building completely free of mold spores requires highly efficient air filtration and is only accomplished in special situations such as hospital operating rooms and manufacturing "clean rooms." Remember, mold spores are in the outside air all the time and some of them will certainly make their way inside buildings. However, it is possible to keep mold from growing inside a building. Moisture control is the key to controlling mold in interior spaces. Air filtration can contribute to lowering mold spores in the air but is secondary to moisture control.
No. Bleach will only kill and decolorize mold; it will not remove mold. Dead mold can still cause allergic reactions and can resurrect itself under the right conditions. Both the Environmental Protection Agency (EPA), and the Center for Disease Control (CDC) agree that bleach or other biocides should not routinely be used to clean up mold. Only anti-microbial, anti-fungal, mildewcide cleaners should be used.
The mold cleanup is finished when there is no visible mold remaining and there is no dust or dirt remaining that could contain large amounts of mold and mold spores. Routine clearance testing for mold is not always necessary but may be required in some instances. Leaving a few mold spores behind is not a problem…if the underlying moisture problem has been corrected. Remember that mold spores are virtually everywhere. Even if all mold and mold spores are removed as part of the cleanup, spores from outside will re-enter that space. Spores will be able to grow as long as water is present.