Exposure to indoor airborne mold spores and toxins commonly occurs, and can cause allergic, toxic, and irritant symptoms and diseases. It is known that mold spores and hyphal fragments are normal components of both indoor and outdoor air. The difference between healthy and unhealthy environment is determined by the amount of mold, the types of mold spores present, and a persons sensitivity or susceptibility to mold. To determine whether the air is contaminated with elevated levels of mold spores and their composition, air samples are collected and sent to an accredited laboratory for analysis.
Air Sampling MethodsThere are two methods for sampling air for airborne mold. Each method has it’s advantages and disadvantages. The method selected depends on the objective of the investigation. At times both methods may have to be used. The most commonly used method is to impact air on an inert clear sticky substance. Airborne particulates including mold spores, pollen, insect parts, skin cells, and others are trapped onto the sticky surface and can be visualized under a microscope in the laboratory. Samples collected using this method are often referred to as nonviable or non-culturable samples. The terms “nonviable” or “non-culturable” are rather misleading but they are supposed to mean that the samples are not cultured in the lab. Nonviable samples are collected using cassettes such as Air-O-cell, Allergenco D, Micro 5, and many other similar cassettes. The second method for airborne mold sampling involves impacting air on some growth media. These samples are normally referred to as culturable or viable samples. Once sent to the lab, these samples are incubated for mold to grow for identification. It is important to know when to collect nonviable or viable air samples. Sometimes you may need to collect both types of samples depending on the data needed which in turn depends on the purpose of investigation.
Airborne Mold Samples Results Interpretation
Interpretation of airborne mold samples results is not easy. The large number of mold species and strains that can occur in indoor environment and the large inter-individual variability in human response to mold exposure make it difficult to set exposure limits. Therefore, the determination of whether or not a building is contaminated is often based on a comparison of the mold spore concentrations and composition in the indoor air with outdoor air. The types of mold present can tell us a lot about the building condition. For example, presence of Chaetomium or Stachybotrys is an indication of existing or previous moisture damage.