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The Toxic Mold Series

Part 2: Testing for Mold?

June 27, 2022

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The Toxic Mold Series

Part 1

Part 2

Part 3

Part 4

DIY Mold Inspection, Preparation for Mold Inspections, and Testing Methodologies

Once you believe that you have a mold issue, validating that belief is suggested prior to engaging a professional. Most mold remediators will test for mold.  In addition, while regulated, the mold remediation business is burdened with some scam artists that will find mold in almost any home.  Mold is ubiquitous and can be found everywhere in any home.  Wherever there is dust, there is mold.  What should be identified is often referenced as “amplified” mold.  Any DIYer can inspect the home looking for visual mold or moisture to provide your first clues.  Water damage is always a concern when it comes to mold.  In addition, another obvious indicator is a musty smell.  DIY Mold Inspection and testing, or hiring a mold inspector, is the next step in addressing your home.


DIY Pre-inspection for Mold

Because mold inspections can be very expensive ($500-$1500 or more), you can do an effective DIY Mold Inspection to share with inspectors or contractors.  While most consumers do not have extensive building science knowledge, searching for visible water damage on walls, ceilings, floors, and foundation isn’t rocket science.  Read more about DIY Mold Inspections HERE. While most consumers do not have extensive building science knowledge, searching for visible water damage on walls, ceilings, floors, and foundation isn’t rocket science.

You can depend on your sense of smell to guide you by paying attention to musty odors.  From there, a flashlight, a phone camera for documentation, and an optional moisture reading are all you need to effectively examine the interior and exterior of the home.  Moisture problems come from building leaks, flooding, plumbing, condensation due to HVAC installation, and high humidity.

Your primary objective should be to identify moisture sources, water damage, and visual mold.  The single most important step is to find the sources of moisture and have them repaired immediately.  Crawlspaces, attics, and basements must also be inspected.  Cleaning and remediation of a home will only be temporary if the problem lies in unconditioned space.Safety precautions are also necessary to ensure that you do not disturb mold where it can result in a significant exposure that will accelerate reaching your body’s Toxic Load.  If you are severely mold sensitive, it is better to have someone else do the testing rather than risking an extreme exposure that can adversly impact your health.



Testing with Purpose

If you desire to test for mold yourself to save money, you will have identified potential moisture issues and visual mold to test for cultured colonies in a mold test plate or mold swab.  The article Mold Testing with Purpose emphasizes the need to identify problems prior to mold testing.  To avoid unnecessary testing, many professionals, and some environmental agencies state that if mold is identified, there is no need to test.  This assumes that the entire home will be repaired, cleaned, and remediated.  At this time, you may want to identify the types of mold present.  Many mycotoxin-producing mold often reproduce from the same sources of organic materials that mold feed on.  You can research your findings or share this information with your physician so they can possibly connect debilitating symptoms to your indoor air quality.

In the event that you hire an IEP or professional mold inspector, understanding their tools is essential in managing the scope and cost of work required to remediate the issues.  It is helpful to have your mold inspector explain their findings while they are inspecting the home.


The Challenge of Testing for Airborne Mold

According to the American Industrial Hygiene Association (AIHA):

The available science for mold testing is incomplete and controversial. Although there are several guidance documents available, there is no accepted national standard. Validated methods to measure contamination are still in their early days, and even when measurement techniques are available, there are no clear benchmarks or standard values to compare the results against. Similar scientific uncertainties exist in the medical diagnosis of mold-related health effects.”1.

The result of this uncertainty is a wide variance amongst mold inspectors in sample planning, mold testing methods, and interpretation of the results.  Each test represents a mere snapshot of the space tested. For accurate representation of the home, different methodologies are used to find an accurate representation of airborne mold and contamination hot spots. A physical inspection is essential to identify moisture problems, water damage, and visual mold.  This includes unfinished parts of the home (crawlspaces, attics, and basements.) Testing must include samples from all areas of the home.  This is because the laws of physics and air ventilation can spread mold systemically.  When this occurs, any potential moisture source coupled with most building materials can become a mold hotspot.   Multiple samples are always required to determine the breadth and depth of a mold problem, as well as to help identify the source of the mold contamination.


ERMI Testing

One particular testing method that is popular is the ERMI test.  ERMI is a research tool developed by the EPA to compare home “moldiness” across geographies.  The EPA explicitly does not recommend its use for mold screening in a home. ERMI requires the collection of dust samples from a specified 6’ x 3’ rectangle of carpet.  The carpet is believed to have accumulated dust from the entire home over time.  This hypothesis has not been proven accurate and the use of ERMI was never intended to represent potential mold exposure in a home.  ERMI testing will result in a single number result on a chart that does not inform any mold remediation planning.

However, one benefit of ERMI was the careful selection of 36 mold species to represent the common indoor air pollutants.  While this panel has become somewhat of an industry standard over the past decade, there has been very little research to identify a better selection and it does not test for many other species of mold that can be harmful to health.

Because ERMI was developed by the EPA, physicians may prefer and recommend ERMI testing.  A single ERMI dust sample from one area will not represent an entire home.  However, the use of several ERMI tests in a home can provide more valuable information.  Unfortunately, at least 3 samples are required for an accurate statistical representation of the home.  At a cost of approximately $300 per sample, the laboratory costs of at least $1,000 will be added on to inspection fees.


Other Testing Methods Using Multiple Samples

There are a several methods mold inspectors choose as their test of choice.  To paraphrase the AIHA position on these methods, none of the methods are foolproof.

  • Petri dishes otherwise known as mold test plates can be used as “gravity” plates to identify airborne mold over an hour.  The plates are then wrapped in foil and left in a dark warm space to incubate for visual inspection or sent to a lab for analysis.
  •  A “Tap Test” can be used to identify mold on a surface.  It is done by taking the agar filled side and tapping suspected moldy surface several times to disturb the colony and release spores directly into the plate agar for culturing. The plates can be individually wrapped in foil and placed in a warm place for incubation or sent to a lab.
  • Mold Tapes simply use the adhesive to collect samples when placed on suspected mold surfaces.The tapes are then analyzed microscopically.
  • Spore Traps.These small cassettes are attached to a vacuum pump that pulls air through the traps. This is done over a 5-15 minute period to gather a better representative sample of airborne mold (however, this is a small snapshot in time). Microscopic analysis follows.
  • Special absorbing mold swabs are very effective in capturing visual mold. They come with a sealable tube for mailing to labs for Microscopic analysis.
  • Polymerase Chain Reaction (PCR) is an advanced testing method to identify mold DNA. PCR is limited to the specific mold being tested (not all molds are tested by PCR laboratories). The mycology community estimates that there are over 100,000 species.This is much less than over a million species estimated by other research methods.  Scientists believe the application of high throughput gene sequencing to fungi will close the gap on these estimates. 34,000 fungi have been sequenced.  Several of these species are commonly found in water damaged homes..  It is possible that mold species that have not been sequenced to date.  Testing will yield negative results for a specific mold. But several molds will likely be present and yield some results.   The most common species associated with water damage can be tested and have yielded successful remediations.
  • CAP 14 test.This method was developed by Dr. Joe Spurgeon, a well-known Industrial hygienist and mold expert.  This method is used to sample specific areas using a mold swab to collect dust and uses 14 mold species that are commonly associated with water damaged homes.  It utilizes ERMI methodology without relying on the overly simplified interpretation method.


Microscope vs PCR

While PCR technology applied to fungal genomics is new to me, I have significant experience in with the same PCR technology as applied to human DNA and medicine.  Statistical validation is a given in human genetics and health care. As in human health, genetic identification, and the ability to clone species can lead to the development of new methods for testing, human diagnostics, or even potential new therapies.

It is indisputable that DNA testing is far more precise than any visual analysis including microscopy.  However, there are trade-offs to consider with testing using expensive methods for a single sample or obtaining multiple with less precise but very affordable methods. For the cost of 3 PCR test samples, approximately 30 samples with lab analysis (Microscopy) can be taken.   The ability to use multiple tests to gain precise knowledge of the location of mold is superior and more effective when cost is an issue.  Otherwise, testing costs could cannibalize funding that can be applied to the removal of the mold.



Microscopic Analysis by Mycology Lab

Microscopic examination of microbials used in most of the sampling methods goes back to the last century and is regularly relied upon today in research, medicine, and environmental inspections.  Microscopic analysis is a “Gold Standard” for most mycology labs and is generally accepted as accurate.  Each genera is identified visually by a microscope.



American Industrial Hygiene Association (AIHA) Position on Mold Testing

“Prior to collecting any air samples for mold spores, the indoor environmental quality (IEQ) professional must determine the purpose and relevance of the sampling as well as ascertain the questions the sampling will answer. Air sampling should be considered as a screening tool or as ancillary to an informed inspection. Testing results should confirm observations or otherwise support conclusions made based on the informed inspection.

In the absence of an informed inspection, air sampling alone cannot support any definitive conclusions. Air sampling for mold spores does not and cannot evaluate potential health risks.”2.

Air sampling using microscopy has limitations when evaluating airborne mold.  Inspectors often prefer to use spore traps to capture airborne spores in the home.. However, a 5-15 minute air collection is still nowhere near representative of the of the concentration of mold spores in a home’s indoor air.  As a result, other techniques such as mold plates, swabs, and tapes can be more effective if used in higher numbers to collect multiple samples from specific areas or materials.


Visual Mold Plate Testing

While laboratory analysis is very important to identify specific molds, visual plates have valuable utility in that you can test any specific area with a gravity or tap test.  Tap testing is simply tapping any suspected surface to disrupt mold spores and capture them directly in the plate agar.  The plates are then wrapped in foil, stored in a warm place for 5-7 days, and are visually examined.  The results are binary.  You will either see mold colonies or you won’t.  You will also be able to count the spore colonies and recognize how many different types of mold are present. Used in combination with swabs, tapes, or other methods, significant information for the entire home can be captured.    Because of the lower cost of mold plates, DIY testing can accommodate sampling of as many areas desired.



I assume that most people are cost conscious today. By understanding methodologies used and the alternatives, you can have a significant impact on the total cost to fix a mold problem. Understanding proper sampling of the home minimizes false positives and negatives and helps ensure that unnecessary demolition and costly renovations that are unnecessary don’t add to the cost.

If you conduct a DIY mold inspection, you may realize that you need a professional to assess the damage, prepare a scope of work to remediate, and take further samples to identify hidden mold (under floors, inside wall, basement, attic, or crawlspace).  Mold inspectors that are not remediators may offer more objective analysis since they are not financially motivated to increase the scope of the issue at hand.

Ideally, you want to be an informed consumer when mold remediation professionals give an estimate.  Scope creep in remediations can turn into very large remodeling projects if not kept in check.  The insurance industry anticipated the impact mold can have on homes.  As a result, most policies protect the insurance company’s interest if mold is not identified and fixed within days of identification. You can avoid unnecessary renovation.  Furthermore, insurance policies often decline mold repairs without very specific evidence and circumstances.  You do not want to be stuck with a large debt.



June Mold Series

The series that provides insight and information for mold sick individuals to inspect, test, and start fixing mold obstacles in their lives.


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  1. American Industrial Hygiene Association (AIHA). The Facts About Mold. Accessed November 2016.
  2. Edwards, Charlotte. Pharma Technology Focus. “The Petri Dish: Telling the Story of Pharma’s Most Humble Ally.”
  3. Wu, et. al. “Current insights into fungal species diversity and perspective on naming the environmental DNA sequence of fungi.”Mycology, May 7, 2019.
  4. S. Environmental Protection Agency (EPA). Mold 2016. Accessed October 21, 2016.
  5. Centers for Disease Control and Prevention (CDC). Mold 2010. Accessed February 10, 2010.