Mold Testing – How to Identify Molds in Your Home

Mold Removal

Mold can have serious health consequences if left undetected and untreated. Mold Testing Colorado Springs should be done when a home has sustained water damage and before any repairs.

Mold RemovalWhen you suspect elevated mold spores in areas not visible such as behind walls or under flooring. When mycotoxin (toxic mold) testing is needed.

Air Testing

Mold spores are in the air and can be inhaled. It is therefore important to include an air sample as part of any mold testing package. The results indicate the level of spores in the air at that location and time. They also identify the type of spores in the air. This is important as some spores are known to cause health issues in certain individuals.

This is often called a “spore trap sample” or an “air quality test”. The sampler works by having a known volume of air pass through the device and impact a sticky surface inside the device. The spores that are drawn into the device stick to the surface and are then captured and analyzed.

There are two types of air tests; viable and non-viable. Viable samples are run with a sampler such as the Anderson Impactor. These are small plastic cassettes that have a narrow slit opening and a sticky surface on the inside. Mold spores are drawn through the slit and then impact the sticky surface and adhere to it. These cassettes are then sent to the laboratory for analysis. The laboratory then opens the cassette and examines the surface with a microscope. The laboratory can identify the number and type of spores present in the air sample but not the specific species.

Non-viable samples are a bit more involved. These are collected with a slit-impact sampler such as the Zefon Air-O-Cell cassette. These are similar to the devices used to collect dust samples for ERMI testing. The technician swabs the air inside the cassette and then wipes it on a special strip that has lines on it for Stachybotrys, Penicillium/Aspergillus, and HERTSMI-2 mold tests. The kits come with the slit impact device, three extra swabs, a lab request card, and a pre-paid mailer.

Typically the inspector will take samples from each of the areas to be tested and also a control sample from an unaffected area for comparison purposes. This allows the investigator to understand what factors may be influencing the results of the tests and to adjust them accordingly. The most important thing to remember is that the test results are only a snapshot estimate of what is occurring at a particular time and place. It is not possible to know what is occurring at other times and places in the home.

Surface Testing

Molds can be found in the air, in settled dust and growing on surfaces of building materials and furnishings. Testing methods can identify a portion of the types of live (viable) molds in a sample by growing them in the lab, but these tests can miss or undercount those that weren’t present at the time and place of the sampling and those that are nonliving. They are also not very good at identifying the species of a living mold.

Surface samples are typically conducted by swabbing, tape lift or bulk sample methods. These are considered the lowest level of scientific confirmation as they only address a small area of potential mold growth. Swabs and tapes can identify the types of mold, but are not able to indicate the size of the contamination. Bulk sampling is better suited to this purpose as it is able to identify the species of a living organism along with its relative quantity within a sample.

These types of samples should only be used if a visual inspection indicates that there is a likely problem and/or the client is interested in learning the species of a particular spore for some other reason (legal reasons, health concerns, etc). The results from surface tests can also be combined with the results from air testing to provide a more comprehensive analysis.

Despite the limitations of all laboratory testing, there are still times when it can be very useful to collect and analyze samples. This can be particularly true if a homeowner suspects that a contractor, builder or previous owner has not properly completed a mold remediation. Samples can be collected and analyzed to demonstrate that the levels of molds that are present in the air have been reduced.

It is important to understand that it is not known how much mold is needed for a person to experience health effects. Certainly, mold concentrations higher than those that are observed in homes with well-controlled ventilation systems can cause occupants to experience symptoms. It is also important to realize that a person’s susceptibility to health problems can vary from one individual to the next, so a single test result may not necessarily be indicative of how a person will react to a particular type of mold.

Bulk Sampling

The best way to find out what type of mold is growing in your home is by examining a bulk sample. This involves removing a piece of the suspected material to be tested in the lab. This is the most accurate method to test for specific species of mold, but it is not always practical. For example, it is not easy to cut up a floor or wall for testing. Fortunately, the same results can be obtained from taking a tape lift or swab samples.

Non-viable air sampling uses a device called a slit impact sampler that runs the air through a small cassette with a sticky surface where the mold spores stick and are drawn into the cassette. The laboratory then opens the cassette and reviews the spores under a microscope. This method gives an overall view of the spore count and may be able to identify the genus but not the exact species.

Viable or culturable sampling requires an incubation process where the spores are provided with a food source to see which ones will grow. This process can be very time consuming and often takes 2 weeks or more for the lab to complete the analysis. Viable samples will identify the genus of the mold and may also be able to identify the specific species as well.

An interesting scenario that we have encountered several times is when a homeowner hires an inspector to perform spore counts and the results are within the normal range. Then, a few days later the same homeowner hires another inspector and receives completely different results. The new result indicates that there is a dangerous problem with the mold.

This discrepancy can be caused by many factors, including different sampling methods and the fact that the actual spore levels can change dramatically from one project to the next. As a result, air sampling can often provide little value in determining the scope of a mold remediation. In our experience, a visual inspection is much more likely to provide valuable information as to the scope of the work that will be needed to address the mold.

Species Identification

Identifying the molds in a sample requires specialized knowledge and experience to be done effectively. Most laboratories will use a series of keys (specialized flow charts leading to the name of the mold) and spores to identify samples. There are also a number of fungus identification books, such as the Genera of Fungi by De Hoog and Guarro (1995), The Genera of Inhabiting Fungi by Samson and Gravesen (1994), The Genera of the Hygienic Fungi by St-Germain and Summerbell (1996) and the Fungi of Interior Environments by Wang and Zabel (1990).

Air sampling is typically performed using a slit impaction sampler which pumps a known volume of air through a tube with a sticky surface inside to collect viable and non-viable spores. The laboratory will then review the spores to identify the type and count of molds. Viable samples require a longer analysis time, often 10-14 days to allow the mold spores to grow and be identified.

Species identification may be necessary when certain fungi produce mycotoxins that pose health hazards in humans. These toxins are usually a result of a fungal infection that is not detected in traditional testing methods. These types of infections are typically seen in immunocompromised patients.

One of the most common mycotoxins produced by filamentous fungi is ochratoxin A, which poses a serious risk for those suffering from liver disease or hepatitis C. This ochratoxin has been shown to cause liver damage, kidney damage and gastrointestinal problems in human subjects. Other mycotoxins produced by filamentous fungi include aflatoxins (B1 & B2), cyclopiazonic acid and kojic acid. These mycotoxins are found in a wide variety of foods and can be found in many different indoor environments.

Filamentous fungi such as Stachybotrys and Trichoderma can be difficult to detect with air sampling or culturable sampling methods. Direct samples can be collected using dust tests or tape lifts but these methods will not identify the specific mold species present. Using advanced molecular techniques such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) can help to identify these types of molds by looking for the presence of certain biomarkers.