Question: I’ve looked at the report and I’m very surprised. There is hardly any results. Have I done something wrong when I did the air sampling?
We had a company selling air cleaners offer to test our air. They did air sampling for for two viable air samples. Then they said we had Aspergillus versicolor. Is it possible that a mold will show up on a viable test and not on a non-viable test?
Answer: I don’t think you did anything wrong in your air sampling. The analysis of the air samples indicated there were some mold spores in your house BUT that is normal for almost every home. Air in every home or building is highly likely to contain some amount of mold spores and other fine particulates. Therefore, air sampling is not used to determine whether there is mold in a building but it is rather used to determine the amount of mold spores present in the air. The reason why one would want to know how much mold is there is because it’s the amount and the types of mold that the building occupants are exposed to that matter.
The air sampling you did and the one that other company did are different in many aspects and hence results from the two tests can be difficult to compare. Unlike the viable sampling method, the test you did does not allow for identification of moulds to species. That’s why we did not report Aspergillus versicolor. However, this method generally gives a better idea of how contaminated the air is because identification and enumeration of spores does not depend on whether the spores are viable (i.e., alive) or not.
I would like to know a little bit more about the viable air sampling conducted by the other company. Did they use an air sampler or just opened the agar plates and left them open for some time? The latter (called the settle plate method) is generally not a very efficient method for air sampling but it’s less expensive to perform and can at times provide useful information regarding the air quality in the home. The second question is, if they used the settle plate method, how many colonies were reported and how long were the plates exposed? The amount and not the presence is very important when it comes to indoor molds. Aspergillus versicolor is one of the most common molds indoors and presence of a few spores/colonies is not an indication of a mold problem. If you have not experienced any moisture problems in your home, it’s very unlikely that you have a mold problem worth worrying about.
As to whether a mold can show up on a viable test and not on a non-viable test, yes, it’s possible.