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Q. Can you tell us what the normal mold spore count range is for air samples.
A. Unfortunately, there are no established regulated guidelines on normal or abnormal spore counts. There is a lot of work being conducted to set guidelines through Environmental Standard organizations and committees. Once these guidelines are established, we would propose to agencies such as the EPA or American Industrial Hygiene Association (AIHA) for approval. In the meantime, we report mold levels as low, moderate, high or very high. Very high would be a contaminated environment. We can also compare the outdoor sample or a comparison in another part of the building and samples taken in similar buildings in the area.
Q. Can you tell us if the mold in our crawl space is toxigenic?
A. The type of mold found on surfaces such as on the wood structure in a crawl space is generally not of a toxigenic nature. (Toxigenic being able to produce toxins.) For example, the toxigenic mold Stachybotrys is commonly found in wet drywall and other paper products such as insulation backing. Wet insulation paper backing in a crawl space may contain this species of mold. Generally, the damp & humid conditions of many crawl spaces are more of a concern than the surface growth we find on the floor joists under a home. The conditions lead to an environment ripe for microbial existence as well as insects and rodents.
Q. What causes mold to grow?
A. Three things are needed for mold to grow: moisture, oxygen and a food source. The food source can be as simple as dirt or dust. Wood or paper products provide ideal fiberous material for mold growth.
Q: What are some of the biological problems I should be concerned about?
A: Molds, mildew, fungi, bacteria and dust mites are some of the main biological pollutants inside the house. Some, such as pollen, are generated outside the home. Mold and mildew are generated in the home and release spores into the air. Mold, mildew, fungi and bacteria are often found in areas of the home that have high humidity levels, such as bathrooms, kitchens, laundry rooms or basements. Dust mites and animal dander are problematic when they become airborne during vacuuming, making beds or when textiles are disturbed.
Q: What are some of the health effects or poor indoor air quality?
A: Allergic reactions are the most common health problems associated with biological pollutants. Symptoms often include watery eyes, runny nose and sneezing, nasal congestion, itching, coughing, wheezing and difficulty breathing, headache, dizziness and fatigue. Dust mites have been identified as the single most important trigger for asthma attacks.
Q: How are biological contaminants transported through the house?
A: Molds and dust mites thrive in areas of high humidity. Mold grows on organic materials such as paper, textiles, grease, dirt and soap scum. Mold spores float throughout the house, forming new colonies where they land. Dust mites thrive on dead human skin cells and in textiles such as bedding, carpeting and upholstery. When these textiles are disturbed during vacuuming, making beds or walking on carpet, the dust particles become airborne. Pollen, plant material that enters through windows or on pets and animal dander also become airborne when disturbed. Infectious diseases caused by bacteria and viruses are generally passed from person to person through physical contact, but some circulate through indoor ventilation systems.
Other Causes of Moisture Problems
Leaky ductwork is not the only way that outdoor air with excessive moisture can enter a house. Many homes have a variety of exhaust appliances, such as clothes dryers, range hoods, and bath vents. Even power roof vents can depressurize the living space if there is an inadequate vent area in the attic.
High moisture levels can be made even worse when there are cool surfaces present, which permit mold to grow. Cool surfaces can result from cold walls below grade, or even from poor air circulation behind furniture or cabinets against outside walls.
Q. Is the “black mold” more harmful than other mold types?
A. Stachybotrys and other several other mold species produce potent mycotoxins whose potential adverse effects on humans due to inhalation exposure are largely unknown. As such, one cannot consider toxigenic fungi as just any other mold. Disturbing mold-infested materials without using personal protective equipment, appropriate ventilation and proper work practices is an inherently foolhardy activity.
Q. Is air sealing & insulation with tight building construction detrimental to indoor air quality?
A. No, this need not be the case. In new, energy efficient homes, and in older homes that have had energy conservation features correctly installed, many pollutants are less likely to enter the homes, and those that do can be removed with controlled ventilation. Energy efficient homes use exhaust fans to remove excessive moisture and cooking odors, and a tight building shell ensures toxins in soil gas do not enter the home.