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Mold Testing – Types of Samples

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expert taking a sample of mold to test

Mold Testing and Mold Inspecting are two totally different services that give you very different results. It is important to know the difference! An inexpensive mold test that doesn’t give you the answers you are looking for is a waste of one’s time and budget.

Mold Test Results

The BIG thing with Mold Testing is “what do the results mean”. Interpretation of lab results is critical where most “mold testers” don’t offer interpretative services. Don’t fall into that trap. Being able to explain what the lab tests mean and its potential deficiencies are critical to developing a mold management strategy or rendering an opinion.

Mold Tests (Types)

There are many types of mold tests available to help identify the organisms we are dealing with and pinpoint the location of a hidden infestation.

ATP – Presence / Absence Pen

Mold Presence/Absence Test Pen

A simple swab applicator with reagent detects the Presence or Absence of mold protein (ATP – Adenosine Triphosphate) to see if Normal Fungal Ecology (NFE) exists. Borrowed from the food safety industry, if it’s green it’s clean. Does not identify the type of mold, but gives a good indication of cleanliness after formal mold remediation or if isolated water stains are contaminated with mold.

ATP – Machine

Mold Testing - Types of Samples 2

ATP Machine

Like the ATP Pen Test (above), the ATP machine is a little more sophisticated and actually quantifies the amount of ATP found in a sample. We use this to establish base levels of microbial presence and routinely check levels during remediation to check our work. Once we get levels down to a satisfactory level we then do a formal clearance test. Otherwise, you are just guessing that you will pass clearance.

Visible Mold TESTS (Bulk, Tape, or Swab Test)

Mold Test Tack Sample

Do you see a dark area that you suspect is mold? If so, a standard Bulk Sample (a chunk of the material), Tape Lift (looks like a clear tape), or Swab test can identify the Genus of this suspect mold. A Bulk sample of the material is great (but not always practical) where the next best is a Tape Lift. Swab samples tend to destroy the organism making it hard to identify under a microscope.

Air Tests (Standard)

Mold Testing Equipment

Using a small low-flow, portable air pump (Like a Zefon BioPump), a predetermined volume of air is taken (from 25-150L) and analyzed against outside control samples. Depending on the particulate debris loading, different volumes of air are used. A dusty environment (like an attic or crawl space) may overload a larger air sample where a small 15-30L sample is best. But a very clean office usually needs more air where a 75L sample would be collected. Airflow speed is critical because a fast draw of air tends to cause spores to “bounce off” the impact plate and not give accurate results.

Air Tests (Wall Cavity)

air test wall cavity scale

Dead air spaces are hidden behind walls, above ceilings, under floors, and often require an air test to detect for hidden organisms. This test is based on a standard air test method where additional cartridges, time, and hidden obstacles often make the test difficult to perform with unreliable results.


ERMI Test Graph

The Environmental Relative Moldiness Index (ERMI) was originally developed by the US Environmental protection Agency (EPA) for research purposes only and is based on dust samples collected throughout a home or building. We often see folks suggesting ERMI tests, but it really shouldn’t be relied on in its entirety. In fact, the US EPA does not recommend its use. Thirty-Six (36) different fungi make up the ERMI test and are species-specific. There are two types of mold groups: Group I (Water damaged homes) and Group II (commonly found in all homes). ERMI does not help identify the mold “Ground Zero” or what the water trigger is. And many times, ERMI does not give you all the answers you are looking for.



The ARMI is an acronym for American Relative Moldiness Index. This test is a more cost-efficient version of the ERMI testing but is not as thorough. This test correlates with the ERMI for predicting the moldiness of homes. 13 different fungi make up the ARMI and are designated a group 1 (water-damaged homes) and group 2 (commonly found in all homes). The fungi identified in the ARMI tests are: Stachybotrys chartarum, Chaetomium globosum, Cladosporium sphaerospermum, Aspergillus Versicolor, Eurotium (A.) amstalodami, Penicillium variabile, Aspergillus flavus, Aspergillus restrictus, Penicillium crustosum, Penicillium purpurogenum, Aspergillus fumigatus, Penicillium corylophilum.


Mold Specific Quantitative (MSQ) Polymerase Chain Reaction (PCR) air testing. Is a fast DNA based analytical method for genus and species level identification and quantification? All DNA based tests tend to be on the expensive end of pricing but can get species-level identification very quickly.

Petri Dish Test

Petri Dish Mold Test

Different molds like different food sources where agar plate cultivation via a Petri Dish is the best way to identify the Genus and Species of a particular mold. But is time-consuming often taking more than 2 weeks to get an answer where molds/bacteria have different agar media preferences.

Environmental Mold and Mycotoxin (EMMA) Testing

toxic mycotoxin Mold Test

A secondary metabolite of mold growth, Mycotoxins is a type of neurotoxin/poison gas that has considerable negative health effects in humans. This gas becomes absorbed and concentrated in building materials, contents, and respirable dust that enters the bloodstream when inhaled. Very specific dust samples are needed (often using a micro-vacuum & a specialized lab) to properly assess for mycotoxins.

Mold Clearance Testing

A series of tests used to help establish if an environment has been returned to Normal Fungal Ecology. Usually conducted after mold remediation has been completed and often is a repeat of the testing done from the original mold inspection. Investigator experience in all aspects of mold investigative & remediation services is critical in conducting this service. For only, an experienced and competent mold professional can render an opinion as to if an environment has been returned to Normal Fungal Ecology.

Here Are The FAQ’s

Helping folks get answers to their Moisture, Odor & Mold questions is a big part of any mold investigation. Here are a few that we hear all the time where you can click here to get more answers to your Moisture, Odor & Mold questions once and for all!

Turn-Around-Time (TAT) & Pricing (Typical)

We typically like around 5 business days to account for shipping, lab availability, and unexpected delays (like holidays). But results can be obtained within 24 hrs where fees are often higher for fast turn-around-times (TATs).

DIY Test – Buyer Beware!

There are many sources (and consultants) available for quick, inexpensive, DIY mold tests. Some are more reliable than others. What’s key is the interpretation of the mold test (what does it mean?). Stay away from testing services that don’t understand the science by providing a detailed interpretation of the labs as it ultimately is a waste of time and money.

Mold Test Cost

Mold testing costs vary depending on what you ask for. Be sure to ask your mold pro what’s the difference. They can explain it to you very easily.

  • DIY Test Kits – $50 – $75, but be careful as they often do not include interpretation of the lab results and recommend you call GreenWorks.
  • Genus Level Sampling – Mold testing from a competent/experienced firm usually runs $75 – $150/sample (non-viable sample where price depends on the type of test).
  • Species-Level Testing – To identify the exact organism $150 – $600/sample & takes more time but is the best way to assess mold impacts with folks suffering from mold health effects.
  • Specialized Tests – Mycotoxin/Endotoxin testing, ERMI, and other DNA type test costs are similar to Species-level testing, but often require a special kit from the lab.

Want The Truth?

If you have a health-related issue involving mold or just want to get to the bottom of your mold issue once-and-for-all, you will benefit greatly from engaging an experienced and competent mold investigative firm that not only knows how to identify hidden sources of mold (Mold Inspection / Assessment) and what type of test to use, but how to correct the problem (Mold Remediation and Hydrology Correction). Only then will you get the answers you need to address the mold and how to prevent it from returning.

Interpretive Considerations for Mold Sampling

It is generally understood that molds are a part of the natural environment and can be found everywhere (indoors and outdoors). Without them, we could not survive. But currently, there are no governmental or international standards for acceptable levels of airborne concentrations of molds or mold spores in an indoor environment. But the experts agree, that visible molds on surfaces within living spaces should be cleansed.

Normal Fungal Ecology (NFE)

As a general rule of thumb, we would like to see our indoor air is at least as good as the outdoor air. We call this Normal Fungal Ecology (NFE) and is established through the use of an outside control sample. Total spores counts are compared along with spore counts of the individual mold genus’ identified.

NFE in an indoor environment may have settled spores, fungal fragments, or traces of actual growth whose identity, location, and quantity are reflective of a normal fungal ecology for a similar indoor environment. NFE is time and season-dependent so having an expert helps account for this.

Statistical Significance

According to the Indoor Air Quality Association’s (IAQA) subsidiary firm’s (Indoor Environmental Standards Organization – IESO) “Standard 2110: Level I Assessment: Standard Guide for the Evaluation of Mold Colonization”, a “significant difference” occurs when total counts of fungal spores/structures are in excess of 10 times the baseline amount (called a “Factor” difference).

A statistically significant difference (10 fold) is a result that’s not attributed to chance. You can learn more here.


There are several considerations to be made before rendering an opinion as to the health of an environment. It is rare where mold sampling alone can be used to render a definitive opinion. Here are the main considerations:

  • The health of the occupants
  • Visual / Olfactory clues
  • Ownership / Remodeling history
  • The current state of the environment
  • Site Hydrology
  • Historic impacts
  • Part of a Property Transaction
  • Sample results

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Avatar for Victor Coppola

Victor Coppola

Victor Coppola is a Building Biologist with decades of diverse environmental experience spanning natural resource management and contaminated sites to Indoor Air Quality (IAQ) and building hygiene matters. He focuses on the three most prevalent issues degrading today's built environment: Moisture Odor & Mold (M.O.M.). Mr. Coppola and his Team are sought out by individuals and professionals concerned about IAQ to those actually suffering from Biotoxin Illness. His hybrid blend of environmental interests and services enable him to give a unique perspective into today's changing environment. Think your home is killing you, better call Victor and his Team at GreenWorks.
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