Some people are very sensitive to molds. For these people, exposure to molds can cause symptoms such as nasal stuffiness, eye irritation, wheezing, or skin irritation. Anyone allergic to mold can develop symptoms within minutes after exposure. There are over 1,000 species of molds and not all are considered bad. Mold needs moisture, oxygen, and a food source to grow and can be found everywhere.
Spore traps are the most commonly used method of collecting air samples to determine if there is a possibility of amplification of mold within a building. The samples are collected using very specific protocols. Training and equipment calibration is necessary to ensure the results are repeatable. One the samples are collected and identified and all relevant environmental data is documented a chain of custody form is completed by the field technician. The samples along with the chain of custody is carefully packaged and shipped to the laboratory for analysis. It is important to understand this is taking a snapshot in time and will document the conditions at the time the samples were collected. Weather, humidity levels, temperature, and how stirred up the air is will all have an impact on sample collection.
There are no federal standards established for acceptable levels of mold found within a structure as there are many factors that can contribute to a healthy or unhealthy environment. In our opinion, there are two primary uses for conducting this type of test. First, the lab will classify mold spores type. There are some types of mold that should not be found within a building and if they show up in the sample more investigation will be necessary. The second use is to determine the overall quantity of mold spores present within the sample. We recommend a minimum of two samples be collected. One from the outside or other control area like a common entryway and at least one sample of the area that is suspected to have a problem like a basement or an area that may have had some water intrusion occur. It's always best to sample as much as possible to draw a more detailed picture of the building being investigated.
Below is a reference table that is used to help understand some of the numbers that will be in any laboratory analysis of a spore trap. This is just a rule of thumb as there are many environmental factors that will impact the overall results. For example, a home in a heavily wooded area near a lake will naturally have higher levels of spores in the air than a home in an arid climate. The center column references the spore counts per cubic meter of air that were in the spore trap. It is desirable to find spore counts of the indoor sample to be less than the outdoor or control sample.
Typical Indoor Mold Spore Concentration Ranges
|Description||Spores (cts/m3)||Predominant Types *|
|"Clean" non-HVAC supplied Buildings.||less than 2,000||Total for all spore types|
|“Clean” HVAC supplied buildings||less than 1,000||Total for all spore types|
|Typical “Clean” Residential||less than 700||
|Possible Indoor Amplification||1,000 - 5,000||Penicillium, Aspergillus, Cladosporium|
|Indoor Amplification likely present||5,000 - 10,000||
Penicillium, Aspergillus, Cladosporium
|Chronic Indoor Amplification||10,000 - 500,000||
Penicillium, Aspergillus, Cladosporium
|Inadequate flood cleanup or active Indoor demolition of contaminated surfaces||50,000 - 10,000,000||Penicillium, Aspergillus, Stachybotrys, Cladosporium, Chaetomium, Basiomycetes, Tricoderma, Ulocladium, etc.|
There are several molds that are known to be extremely hazardous to humans. They consist of Chaetomium (pronounced Kay-toe-MEE-yum) and Stachybotrys chartarum (pronounced Stack-ee-BOT-ris Shar-TAR-um). These types of mold are found naturally in the woods and are important to help decompose dead organic material but should not be present within a building. You can see in the table above these types are typically found within buildings that have experienced flood damage.
It is important to control the overall relative humidity levels within the home to be within 20% to 65%. That may mean you will need to run a dehumidifier during the summer months, regularily maintain and adjust your whole home humidifier during the winter months. Ensure your bathroom and kitchen fans exhaust the indoor air to the exterior of the building and not into the attic space. And keeping your gutters clean and gutter extensions at least 5 to 10 feet away from your foundation. We have also seen homes that use a dryer duct bypass that diverts the dryer exhaust back into the home. We do not recommend using these types of devices at all. If you see condensation or ice forming on the inside of your windows at anytime is a good indication that you have to much moisture in the air. Good housekeeping and regular home owner maintenance will help you reduce the likelihood of mold contamination within your home. Medical questions about mold are for the Health Care Professionals to address.