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Why collect mold samples?

Written by Ralls Melotte

  1. One might assume that if you can see visible evidence of mold in a building, why would you need to sample it?  But is it really mold?  Most things that look like mold are probably mold, but soot from candles and oil lamps as well as dust have often been miss-identified as mold.  There is no point in conducting mold remediation if you really don’t have a mold problem.  Lift samples can be taken and analyzed fairly inexpensively that will identify the genus families of mold present.  Although most mold consultants do not take lift samples regularly, it sometimes is the best way to make sure what you are attempting to remediate is actually mold.

  2. People who are buying a home or a new building, whether new or old, sometimes want to know if there is a hidden mold issue.  Air sampling is a quick way to verify if airborne mold levels in a building are at acceptable levels and not sufficiently elevated to be a potential health concern.  Seeing that mold is always present in outdoor air due to air infiltration, there will always be some level of airborne mold in buildings.  Since there is no established guideline for how much mold in air is unhealthy, samples are taken at representative spots in a building and compared to one or two samples from the outside.  The results of the mold samples taken inside should be less than what is found outside.  Otherwise, the results probably indicate that mold is growing in the building and is not the result of unavoidable air infiltration.  The interpretation of the analysis results requires someone that is familiar with mold sampling protocols as well as the idiosyncrasies of mold growth.

  3. What about those inexpensive mold kits you can buy at the hardware store?  It is very difficult to interpret the results from those kits.  Since mold is always in the air, both inside buildings and outside, those kits will always show mold growth.  There is no way to verify if the mold growth represents a reasonable amount of mold or if it is elevated.  In the end, one is left with no further useful information than before you used the kit.  Air sampling analysis provides actual quantities and types (genera) of mold so you can make a comparison of the levels of mold at different locations both inside and outside.

  4. Since the only way to evaluate whether interior mold sample levels are acceptable is to compare them with outside samples, there are times when one shouldn’t collect samples.  During a rainstorm or within 24 hours of a rainstorm, mold levels outside will drop dramatically since the rainfall is driving the mold spores down to the ground.  Obviously, the rain is not having the same impact to the inside mold levels.  If air sampling is conducted during rainy periods, a realistic comparison cannot be made between inside and outside levels so the results of the analysis don’t mean much.  In a similar way, samples taken in very frigid weather will be quite low outside and the inside levels should be reasonably lower than the outside as well.  Thus, if you were to compare results of samples taken during winter to samples taken during a milder weather period, it might look like the problem has gotten worse when all that has happened is that you now have air from the outside in the building that has considerably greater quantities of mold.  Samples taken in a rural area during high, dry winds, particularly during the harvest season, will have exceptionally high levels of mold and due to air infiltration, levels inside could be escalated as well.  Samples collected near rivers and lakes or marshes are bound to have higher outside levels.  All of these factors need to be taken into account before making a determination of whether the interior samples are at acceptable levels.  You really need a professional with mold experience to interpret the results of any air sampling.

  5. What if there is a funky odor in a building but there is nothing visible that looks like mold?  Mold can grow rapidly in hidden locations, such as on the backside of drywall or in floor cavities.  Air sampling will pick up the mold spores and hyphal fragments (dead mold fragments) from the air.  They tend to be in greater concentrations in the vicinity of where the hidden mold is growing.  This gives an Inspector an indication of where to look more closely for moisture damage.

  6. Although many people are most concerned about cleaning up mold, mold is only the symptom of an ongoing problem.  Consequently, simply cleaning up the mold is only a temporary solution if one hasn’t corrected the condition that caused the mold to grow in the first place.  This is where a thorough investigation of the home by someone familiar with construction, including a careful interview with someone familiar with the maintenance history of the building is essential before a sampling protocol is established.  Unlike the situation outlined in item 2 above where the primary goal is to establish if mold is present above acceptable levels, trying to locate the cause of high levels of mold requires that the sampling protocol is designed to allow the inspector to establish as quickly as possible the source of mold growth.  The initial inspection and the history of the building will help the Inspector to focus on the possible causes of moisture damage that might be supporting the mold, allowing him/her to concentrate on sample sites that will prove or disprove his/her theory.

  7. If no one seems concerned about the mold growth, is it necessary to do anything?  As indicated in item #6 above, mold growth is almost always an indication that a material that isn’t designed to be exposed to moisture is repeatedly getting wet.  Mold feeds on organic material.  You can even find mold growth on glass and non-organic materials because it is growing on dust that has collected on inorganic materials.  Once established, mold does not go away on its own.   If the material stops getting wet, the mold will become dormant, but will start growing again as soon as there is enough humidity in the air to support continued growth.  If the mold is growing on an easily cleanable finish, such as a counter top, glass, ceramic tile, etc., it can be wiped off.  On other surfaces that are not easily cleaned, the mold grows into the porous surface and starts the process of rotting the material.  Over time, this can cause major problems if not corrected.  The porous wood on the backs of cabinets, particularly behind sinks, the cardboard surface on the back of drywall, fabrics and the backing of carpeting are difficult to clean and will require removal and disposal.  If there are large areas of mold damaged material, just trying to clean or remove the material will release large amounts of spores into the air, potentially causing mold growth in other areas of the building.  Correcting the moisture damage problem and either cleaning or removing the mold growth is the only way to ensure that the problem doesn’t get worse over time.

  8. All molds are allergens, so anyone with a sensitivity to mold or individuals with respiratory concerns, asthma or an immune system weakness may respond more dramatically to exposure to elevated levels of mold compared to others.  Those reactions can include eye irritation, excessive nasal drainage or inflammation of any mucous membranes.  Infants that have not developed an immunity to mold and elderly that may have lost their immunity are more likely to react strongly to elevated levels of mold in the air.

  9. Certain diseases can be caused by mold exposure and should be discussed with a physician with mold related disease experience.  In those cases, more than just the genus of the mold present may be needed to complete an evaluation.  The species of mold can only be determined through a different type of sample collection called Viable mold sampling.  Unlike the more economical air sampling discussed in the paragraphs above (Non-Viable sampling), Viable sampling is more costly and takes about a week of incubation to have results.  As the mold grows from a Viable sample in the sample media, the growth pattern and resulting spores are used to identify both the genus and Species of the mold.  The end result of this type of sample collection and analysis might be Aspergillus Niger instead of just the family or Genus of mold, Aspergillus.  This method of sampling is normally only needed to define a particular Species of mold that might be capable of causing a mold related disease.  Because it is totally dependent on spores going through a complete reproductive cycle, it is not used as often to establish the potential for more common mold health issues.  Viable Sampling does not provide a way to quantify the results; it does not establish an easy to evaluate number such as Counts/M3, in the air.  It only establishes which Species of mold capable of reproducing are present.  It should be understood that even fragments of dead mold, hyphal fragments, are as likely to cause allergic reactions as the spores themselves.

  10. Mold requires a suitable organic material to grow as well as moisture and temperatures between 40- and 100-degrees Fahrenheit.  Under these conditions, mold can establish itself within 48 hours.  After that, even if the moisture is removed, the mold can continue to grow slowly just on the humidity in the air.  Since these conditions can be found just about anywhere inside and outside buildings, mold is a fairly common element in our environment.  Mold performs an important function in the environment since it causes the decomposition of all organic material. Without mold, there would be no soil, just dead trees, animals, etc.   But inside a building, it is something to be avoided wherever possible.  Air sampling is just one way of verifying that mold has or has not accumulated in a building to a level that might be a health hazard to certain individuals.

Mold, Asbestos, & Lead Paint Consultant