Cashins & Associates Blog

Indoor Air Quality and Mold Sampling

Posted by Mike Cashins on Fri, May, 31, 2013 @ 10:05 AM

Mold_TestingThere is much confusion surrounding mold air sampling – when to do it, what it means, methodology, interpretation of results, and the like. This article is meant to shed a little light on when and how mold sampling should be conducted.

Firstly, mold air testing is not an exact science. Mold spores are everywhere. They are indoors, outdoors, and in between. You breathe them in with every breath you take. So, just because you sample for mold and find some, don't panic. It just means that you live on planet Earth.

Many times, mold sampling is simply unnecessary. Mold doesn't just spontaneously come to being. The right environment must be present for spores to colonize and for fungi to grow. For mold growth to occur, two things must always be present – food and water.

Mold must have something to eat, and that something must be organic – that is, it must be carbon-based, not synthetic. Mold will not grow on concrete, linoleum, or plastic. It requires the sugars provided by such natural materials as paper, cloth, or wood. Sometimes mold is seen growing on these non-organic materials but in these cases it is growing on a layer of dust that has built up on the surface.

Secondly, it requires water. For mold to become a real indoor health problem, quite a bit of water is necessary. So, if you don't have reason to believe that excess moisture has entered your building (e.g. you haven't had a history of flooding or haven't had a pipe burst), you really don't need to worry about mold. There are exceptions of course; e.g. improper ventilation causing excessive condensation, elevated humidity in an area with lots of paper or cardboard. However, in most cases if there is not a significant water issue the mold concentrations would be expected to be similar inside as found in the ambient outdoor environment. In most cases the airborne mold levels are lower indoors than outside. This is particularly true of mechanically ventilated structures.  

An instance in which sampling is, for the most part, unnecessary is when the mold is visible. Many times we are asked to come sample the air in a building where visible mold has been identified. The question is – why? Why sample for the presence of something you know already exists? Well, you may say, shouldn't we find out what type of mold it is? You know, to make sure it isn't TOXIC BLACK MOLD? My answer to this is "no". The type doesn't matter; visible mold on an interior building surface is an issue and must be dealt with regardless of the type.  And as for the "Toxic Black Mold" phenomenon, this was a hyped up media driven conclusion. Certain molds do generate more mycotoxins than others but for the most part they all must be handled in a similar manner. The only benefit of determining the mold type is to target that specie of mold in possible post remediation verification sampling.

So, you may ask, when is air sampling recommended? The truth is – not very often. The U.S. Environmental Protection Agency (EPA) has stated that the best way to perform a mold assessment is visually. Almost all moisture and mold related problems can be confirmed simply by knowing where to look and then looking there. Many times, air sampling complicates and confuses things, turning something that should be rather straightforward into an expensive and confusing ordeal.

Air sampling for mold is recommended when there has been excess moisture inside a building for a period of time and where it is suspected that "hidden" mold growth may exist, that is, growth on the backsides of walls or within HVAC systems that is not readily visible. However, even in these cases, air sampling may not reveal the problem. Mold only releases spores when it is dry and dormant, not when it is wet and actively growing. Further, if the growth is contained inside the wall, it may very well have no direct impact on occupants at all, and may not show up in air samples. Air sampling might be warranted if there are sensitive individuals that cannot be exposed to elevated levels of mold due to health concerns. It can also be used to show concerned occupants that the cleanup was done appropriately.

If mold sampling is to take place the decision must be well thought out. The following is strongly recommended:

  1. Do not use the do-it-yourself tests found at home improvement stores. These are a complete waste of money and are of no use whatsoever.
  2. Hire a competent indoor environmental professional. It is ideal that the individual be board certified by the American Board of Industrial Hygiene (ABIH) or by the American Council for Accredited Certification (ACAC). Further, the professional should have extensive knowledge of and experience in conducting microbial air and surface sampling. These professionals will ensure that the proper sampling technique and sufficient number of samples are collected to make a proper determination of conditions.
  3. Ideally, both "viable" and "non-viable" sampling should be conducted. "Non-viable", or spore trap sampling, collects air onto a cassette, which is then sent to a laboratory for analysis. The analyst then identifies types of mold and counts the number of spores per microscopic field. The results are presented as spores per cubic meter of air. "Viable" sampling involves the impaction of air onto a petri-dish. This dish is kept cold after sampling and is sent to a laboratory using cold packs and a cooler. The laboratory cultures the plates, and expresses the results in number of "colony forming units,” or "CFUs". Spore trap sampling reveals the presence of all spores, whether dead or alive. The analyst, however, is able to identify the mold only down the genera level. Viable air sampling ignores the "dead" spores (since they don't end up growing on the petri dish), but allows the analyst to identify the mold down to the species level.
  4. Multiple samples must be collected at each location. Because mold spore types and concentrations fluctuate greatly throughout a day, at least three samples should be taken at each location at different times. Far too often we have reviewed reports where someone has collected one five (5) minute air sample and has based recommendations on this result. This is woefully inadequate and a waste of time. At minimum several air samples are required to even attempt to make any determination pertaining to mold air concentrations.
  5. Both "complaint" as well as "non-complaint" areas must be tested. Because there are no regulations as to how much mold should be in the air, the interpretation of results comes down to comparing types and levels of molds in different areas. This means comparing mold found in the air in areas where a problem is thought to exist with those taken from an area thought to be "normal". Sometimes outdoor samples are taken for comparison. Many times this is acceptable, but many variables (such as snow cover, wind, recent precipitation, etc.) can cause inconvenient jumps or dips in spore load. Using outdoor concentrations is under dispute\criticism by many professionals. In our opinion it is sometimes helpful but is only one piece of the whole assessment. Too many times we see people using the outdoor\indoor comparison as the primary decision driver; this in our view is a mistake.
  6. The samples must be sent to a qualified laboratory that is AIHA LAP LLC accredited.

In addition, a mold assessment should never be performed without considering other elements of the indoor environment that may be contributing to poor indoor air quality. Mold air sampling should never be performed in isolation, but should be one part of a comprehensive strategy designed to identify real problems that may exist in a home or building.

Cashins & Associates prides itself on its approach to assessing indoor environmental quality. Our board-certified professionals have decades of experience performing such evaluations. If you think you may have a mold problem, please call us. But whatever you do, please don't buy the home mold sampling kit. This is a settling plate that will report you have mold; well of course you do mold is everywhere! The information provided by these tests is useless.

If you have a mold or moisture issue in your building we would be happy to help. Please fill out our convenient and easy web inquiry form and a professional will respond withint 24 - 48 hours. For more on general indoor air quality parameters download our paper here. 

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Topics: indoor air quality

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