A Practical Guide to Indoor Mold and Mold Testing

MOLD is pervasive.  It is a fungi found both indoors and outdoors.  There are thousands of species of fungi – the good news is you only have a few which are typically related to indoor air quality issues. That is why you need to understand mold testing.   I. Mold and Effects on People: What genus of mold are we concerned with in our indoor environment?  Mostly, we are concerned with the water indicator molds such as Stachybotrys, Chaetomium, Memnoniella, Trichoderma and Ulocladium and one common indoor mold, Aspergillus, which can thrive on elevated humidity levels.  These are the most common molds we find which can pose a possible health threat or which represent possible damage to the structure.  Any mold which can release spores containing mycotoxins can be allergenic to some people. Toxins related to mold have different exposure levels and do not affect all people the same.  Generally, children, the elderly and those suffering from pulmonary distress or disease which has weakened the immune system are most affected.   Common medical complaints related to mold exposure include shortness of breath, headache, anxiety, depression, memory loss, visual loss, muscle and joint pain.  Some may experience gastrointestinal complaints.   Mycologists classify molds into three groups based on human responses:  
  • Allergenic molds: Rarely life threatening but pose a problem to asthmatics.
  • Pathogenic molds: May produce an infection such as Aspergillus fumigatus
  • Toxigenic molds: Produce mycotoxins which can pose serious health threats to many.
  Mycotoxins interfere with RNA synthesis and is believed to be associated with damage to DNA.  Mycotoxins are lipid-soluble and readily absorbed by intestinal lining, airways and skin.  Researchers are most concerned with mycotoxins known as trichothecenes which are produced by Stachybotrys chartarum and Aspergillus versicolor.  In addition to trichothecenes, researchers are concerned with aflatoxins which are found in grains, hay, and decaying vegetation.  Aflatoxins are also found in our food such as legumes, peanuts, corn, soy beans and others.  We are most concerned with Aflatoxin B1 as it has been linked to liver disease, cancer and even death.  Aflatoxin is produced by Aspergillus flavus and Aspergillus parasiticus. These molds would rarely be found in a home but could be present in a barn which stored feed.   If you have elevated mold in your home, there is an underlying reason for it.  Simply knowing you have elevated mold does little to help you – you need to know why it is present and how it can be eliminated.  To understand why we must have the knowledge and experience to identify the type and threat level and be able to determine the underlying reason it is present – then, we can determine how it can be eliminated.  You will need an experienced mold assessor who is qualified to assess the structure.  One without the other does little to resolve your problem.  The task of the mold assessor is not to detect mold, but rather to detect the amplification of mold in the indoor environment.  Hiring someone to simply conduct “air sampling” is a complete waste of your money and may, in fact, produce false negatives which may hide a real issue or overstate the issue.    II. Before you hire a “mold tester” there are a few things you should understand:  
  • Water indicator molds such as stachybotrys or ulocladium (what we call the “sticky molds”) rarely show up in an air sample. The spores from these molds require mechanical agitation to release so unless they are being physically disturbed, you may not know they are present.  When they do show up in an air sample, they are often, mistakenly identified or they originated outdoors.  Do not allow a “mold tester” to sell fear when they disclose stachybotrys in an air sample.  This is a guaranteed indication your “mold tester” may not know what they are doing.
  • Anyone selling “mold testing” or “mold sampling” is probably not licensed by the State as a Mold Assessor. They are taking advantage of a loophole in the law which allows anyone to “test” mold less than 10 square feet.  This law was established to benefit property owners and it has been exploited by those who wish to sell “mold testing.” It is a common add-on service by home inspectors who have no knowledge or experience in mycology and who are not insured as a licensed Mold Assessor.  They simply want your money.
  • Only a licensed Mold Assessor can provide you with an assessment of the condition in your property. What good is a barely qualified laboratory report unless you understand what it means?  Why would you pay a “mold tester” to provide a lab sample report which, by law, they cannot interpret?
  Most “mold testers” take a comparative sample between outdoor and indoor mold genus.  This is referred to as the Reference Method of airborne sampling.  They present the samples to a lab who will determine your home is either Elevated or Not Elevated based solely upon the comparison between the two samples.  There are many problems with this type of assessment and the results are rarely correct.  Here is what you should understand:  
  • The samples are compared at the genus level and do not identify the species. For example, there are several hundred species of aspergillus mold but we are generally only concerned with four species ( fumigatus, a. flavus, a. versicolor and a. niger).  These four are the species which typically relate to infection which may lead to aspergillosis.  The air sample does not distinguish which species of aspergillus was detected as it only identifies by genus.  Thus, the sample may indicate a concern where none is present.
  • The outside air is constantly changing and simply taking one air sample does not reflect the actual mold levels present.
  • Generally, the “mold tester” has no idea of who has been in the home, how many times doors/windows have been opened, if the home was just vacuumed or any other control measures, to include running the AC system.
  • Often home inspectors will sell air sampling for mold following a home inspection. They offer it as “peace of mind” or after finding “unidentified mold” on air handlers in the garage or around AC vents.  The first thing you should know is mold does not grow on metal and what they are seeing is wet dust.  Yes, there could be a few settled mold spores on the dust (mold is naturally occurring) but it poses no threat to you or your home.  This condition almost always relates to an aged or faulty AC system.  Wipe the “dust” off and fix your AC unit.  Further, during the home inspection they have opened windows and doors numerous times and the home is basically filled with outdoor air – hardly the best time to sample.  Sampling in this situation is basically worthless and a waste of your money.
  • “Mold testers” have no training in mycology. Weather, temperature and the time of day can affect sampling results for different mold species:
   Stachybotrys and acremonium release spores during a rain (physical agitation).  Thus, if a mold tester pulls an air sample following a rain it is probable there could be a few spores of stachybotrys present, but it does not mean you have a mold issue.   Ascomycetes and basidiospores release spores after a drop in the relative humidity (rain or darkness). Sampling first thing in the morning or following a rain will almost always provide increased counts.   Alternaria, cladisporium and epicoccum release spores on dry, windy days.  If your home inspector advises you need a “mold test” on a dry, windy day, following a home inspection where the doors and windows have been opened, you may very well see elevated counts of these molds.   Why is this important for the air sampler?  Because, these molds can release 50,000 spores/um at a time and there may be many present.   Mold is a symptom of a building related condition.  To control mold, you simply remove the moisture.   III. Here are a few examples of when you do not need a mold assessment:  
  • You had a water event such as a broken water pipe or toilet overflow. Remove all water damaged materials, dry the area and have the plumbing repaired.  Unless you see visible mold, restore your home.  You do not need to hire a “mold remediation” company either.  Call the plumber to fix the piping and then call the appropriate trade, i.e., drywall contractor or flooring contractor.
  • You see what looks like “black mold” on the air handler or on the ceiling around your AC vents. It is not mold – it is wet dust.  This relates to your AC system not properly removing excess water vapor/humidity from the air.  It is an AC issue – call an AC contractor to evaluate your system for repair/replacement.  Once done, clean the affected areas with common detergent and if needed, treat the drywall/ceiling with Kilz and re-paint.
  • You see a build-up of what appears to be “mold or fungus” on the inside of your air handler (generally around the A coil). This is not mold but it is a build-up of fungus which could have harmful bacteria present.  Have the unit cleaned and serviced by an AC contractor.  No, you do not need to test the fungus.
  • You see “mold” on any metal surface. Mold cannot grow on metal – there is no food source.  Clean the surface with a simple detergent.
  • You see “mold” around the sides or bottom of a bathtub or shower. This generally relates to water getting splashed or leaking around a shower door/curtain.  It is common and almost never relates to a mold issue.  Clean the area with a disinfectant such as Lysol and allow the area to fully dry.  Now you need to caulk the shower door/wall/baseboard and generally re-paint.  If water persists, you may need new shower doors, better shower curtains or a better clean up after the kids take their baths.  If you dry the area and do nothing further, the “mold” will disappear once the moisture is removed.  If it persists, you may have a leaking shower pan or leaking piping so you would want to consult a plumber in that situation.
  • Common “mold” found beneath kitchen sinks or bath sinks almost never relate to a “mold issue”. It relates to opportunistic mold spores settling on wet dust due to some level of plumbing leak.  Call a plumber to repair the leak and clean the area with Lysol and allow it to dry.
  • Mold/mildew found on clothes in your closet relates to poor ventilation or the lack of return air vents. This is common in older homes which may have a supply vent delivering cold air into the closet but no return.  The cold air creates water vapor in the area which is not being returned to the air handler.  This mold is most often aspergillus which thrives on water vapor.  You will need to clean all clothes, shoes, handbags, belts and anything else stored in the closet and improve the ventilation in the closet. Leather goods with a significant build-up of visible mold should be thrown away – you cannot clean them. Sometimes ventilation can be improved with louvered doors, providing an open vent between the closet and the bedroom (generally by installing a vent above the door) or having a return vent installed by an AC contractor.  Until you fix the ventilation issue, you will continue to have mold in the closet.  We find this situation commonly occurs after a homeowner has had new insulation installed (especially spray foam insulation) or they have “upgraded” their AC system by a contractor who failed to properly evaluate the home.  You may want to call that contractor and ask them how they intend to fix the mold problem they created.  You don’t need a mold assessment – I’m telling you right here that you have aspergillus mold and how to fix it.

image for mold testing helpful tipDo not have your home re-insulated without understanding how it may affect your indoor air quality.  Older homes rely upon air movement – that is how they were designed.  Newer homes rely upon closed, conditioned systems.  When you circumvent the design by drastically increasing insulation or installing new AC systems, the whole home should be evaluated for impacts on air quality, moisture control and ventilation.  I see many homeowners develop air quality problems after spending thousands of dollars on “improvements.” This is especially true with crawlspace encapsulation.

  Do not hire a mold tester or assessor unless you understand what their credentials are.  The State of Florida requires, as a minimum, anyone who physically samples or identifies mold for a fee must be a Licensed Mold Assessor and maintain $1 million in Errors & Omissions insurance for mold assessment.  That is the minimum qualification by law.  In addition, you should make sure the licensed assessor has additional qualifications and experience.  Are they…   Council Certified as an Indoor Environmental Consultant Hold additional licensure such as a Certified General Contractor Hold certification in microbial/fungal microscopy   If the person conducting the site investigation is a sample technician, do they report directly to a licensed Mold Assessor who has trained them and who supervises their work?   If the answer to the above is No, you may have an unqualified person testing your property.   An experienced Mold Assessor will be able to take and read samples on-site to assist in determining any threat level present.  Further, they will have access to specific test instruments such as particulate meters to assist in their evaluation.  An air sample pump and a thermal camera are the last instruments an experienced assessor will bring to the job.   Don’t be victimized by unscrupulous “mold testers” who simply want to take your money while providing worthless information in return.  

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