How to Test for Mold: Different Types of Samples

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How to test for mold

It’s no secret that mold can be an extremely frustrating issue to deal with. In small amounts, mold can be unsightly and unpleasant. But large patches or toxic species can have devastating repercussions. Not only can be it destroy your property, but long-term exposure to toxic mold is also extremely damaging to your health.

Now, mold is incredibly common in homes and all types of buildings. It’s estimated that around 70% of homes in the US have at least some mold growth. But often, this mold can be hidden in spots where you can’t see or smell it. Further, some molds are incredibly toxic and shouldn’t be cleaned without protection.

But how can you know which kind is growing in your home? The answer is that you need to know how to test for mold.

During a mold test, experts will gather samples and send them to a lab to determine the type of species. Mold testing and mold inspections are two totally different services that give you very different results. Investigators are looking for physical signs of mold growth during an inspection, whereas a mold test confirms the exact kind of mold growing or whether it has been removed completely.

There are many DIY options for mold testing that you’ll see on the shelves of your local hardware store. But an inexpensive mold test that doesn’t give you the answers you are looking for is a waste of one’s time and budget.

Instead, it is highly recommended that you hire a professional to handle the job. Otherwise, you could be breathing in toxic mold without even knowing it!

Here’s everything you need to know about how to test for mold the right way.

1. Types of Mold Tests

If you schedule a professional mold test, inspectors will come to collect samples from the areas where mold growth has been confirmed. These are also conducted once mold remediation work has been done to confirm that all traces have been safely removed.

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.

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

Mold test tack sample

If you can visibly see a dark stain on your wall or floor that you suspect is mold, then a Bulk Sample test is likely your best next move. A standard Bulk Sample takes a bit of the material (such as a piece of carpet, flooring, or drywall) for testing. This can also be collected as a Tape Lift or a Swab Test.

This will identify the Genus of this suspect mold. A Bulk sample of the material is typically the best, as it tests a larger sample. But this is not always practical, as you may not want to cut up your floor, wall, or carpet. Tape Lifts are the next best option, while Swab Samples tend to destroy the organism making it hard to identify under a microscope.

B. Air Tests (Standard)

Mold testing equipment

Mold spores can become airborne, so in some cases, an air sample can be used for detection and identification. A low-flow portable air pump collects a predetermined volume of air is taken (usually between 25-150L) and analyzed against outside control samples.

Depending on the particulate debris loading, different volumes of air are used. For example, 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.

C. Air Tests (Wall Cavity)

Air test wall cavity scale

Dead air spaces are hidden behind walls, above ceilings, and under floors are tricky to gather physical samples from, so air samples are more commonly used. This test is conducted similarly to a standard air test method, but often multiple cartridges are gathered for a more accurate result.

D. ERMI Test

Ermi test graph

The Environmental Relative Moldiness Index (ERMI) was originally developed by the US Environmental protection Agency (EPA). This index was used for research purposes only and is based on dust samples collected throughout a home or building.

An ERMI test uses dust to determine the likely amount of mold present in an area. It uses DNA-based methods to determine the mold type.  We often see other mold inspectors suggesting ERMI tests, but it really shouldn’t be relied on in its entirety.

In fact, the US EPA itself 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’s origin, and the measurement results are not always accurate.

E. ARMI Test

The ARMI is an acronym for American Relative Moldiness Index. This is another type of DNA analysis that can determine the species of mold and the likely amount of mold in the property.

Armi test

This test is a more cost-efficient version of the ERMI testing but is not as thorough. There are only 13 different fungi that make up the ARMI, and they are designated as 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 variable
  • Aspergillus flavus
  • Aspergillus restrictus
  • Penicillium crustosum
  • Penicillium purpurogenum
  • Aspergillus fumigatus
  • Penicillium corylophilum


Mold Specific Quantitative Polymerase Chain Reaction (MSQPCR) is a faster mold analysis test, as it detects unique DNA sequences rather than mold spore counts. This type of testing is also split into two groups, with one being mold commonly found in water-damaged properties and group two being more common household molds, such as:

  • Acremonium strictum
  • Alternaria alternate
  • Aspergillus ustus
  • Cladosporium cladosporioides v1
  • Cladosporium cladosporioides v2
  • Cladosporium herbarum
  • Epicoccum nigrum
  • Mucor & Rhizopus group
  • Penicillium chrysogenum
  • Rhizopus stolonife

While this is a highly accurate form of testing, all DNA-based tests tend to be on the expensive end of pricing.

G. Petri Dish Test

Petri dish mold test

Some types of mold are best identified by letting the mold consume various food sources through agar plate cultivation on a Petri Dish. Mold samples are collected and then observed via a microscope to see how it develops depending on the nutrition source.

This provides a highly accurate result, but it is quite time-consuming. In most cases, it can take over two weeks to get an answer.

H. Environmental Mold and Mycotoxin (EMMA) Testing

Toxic mycotoxin mold test

Mycotoxins are a type of neurotoxin/poison gas that has considerable adverse health effects in humans. A secondary metabolite of mold growth, this gas becomes absorbed and concentrated in building materials, contents, and respirable dust. This can enter the bloodstream when inhaled.

Very specific dust samples are needed (often using a micro-vacuum & a specialized lab) to assess for mycotoxins properly.

2. Mold Clearance Testing

A series of tests are 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.

Generally, this is determined by one of two types of tests:

A. ATP – Presence / Absence Pen

Mold presence/absence test pen

One of the easiest ways to gather a mold sample is with a simple swab applicator. The tip is covered in reagent, a substance used for chemical analysis. This detects the presence or absence of mold protein (ATP – Adenosine Triphosphate) to see if Normal Fungal Ecology (NFE) exists.

One of the greatest benefits of this type of mold test is that it provides a nearly instant result. The swab tip will turn green if no mold is detected within a few seconds.

However, it is important to note that this does not identify the type of mold. But it does give a good indication of cleanliness after formal mold remediation or if isolated water stains are contaminated with mold.

B. ATP – Machine

How to test for mold: different types of samples 1

While similar to the ATP Pen Test, the ATP machine is a little more sophisticated and quantifies the amount of ATP found in a sample. Mold testing services use this to establish base levels of microbial presence and routinely check levels during remediation to check their work.

Once these levels get down to a satisfactory level, they can complete a formal clearance test. This eliminates any guesswork and ensures that the mold has been completely removed from the premises.

3. What’s the Best Way to Test Your Home for Mold?

If you suspect that mold is growing in your home, office space, or property, you need to act quickly. Getting a mold inspection and test will determine your next course of action for removal and remediation.

But which testing method is the best? There is no clear answer – each type of test has its own strengths. So, there are some things to consider when narrowing down your testing options:

A. Turn-Around-Time (TAT)

You’ll want to hire a mold testing company that provides quick results. At GreenWorks, we typically deliver results in 5 business days to account for shipping, lab availability, and unexpected delays (like holidays). But results can be obtained within 24 hours if needed. Extra fees may be incurred for fast turn-around-times (TATs).

B. DIY vs. Professional

Many at-home systems are available for quick, inexpensive, DIY mold tests. Some are more reliable than others. However, this is far less accurate than a test conducted by mold testing professionals. It is quite easy to contaminate or fumble a sample.

Ultimately, we recommend that you stay away from testing services that don’t understand the science by providing a detailed interpretation of the labs. Ultimately, at-home tests are a waste of time and money, and it’s best to book a professional from the start.

C. Mold Test Costs

Mold testing costs vary depending on what you ask for:

  • DIY Test Kits – $50 – $75, but be careful as they often do not include interpretation of the lab results.
  • 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.

4. Mold Test Results

Interpretation of lab results is critical where most “mold testers” don’t offer informative services. Unless you’re a mold expert yourself, these lab results will seem incredibly confusing, and they won’t provide any direction towards what your next steps should be.

Understanding what the lab tests mean and their potential deficiencies is critical to developing a mold management strategy. Here are some things you need to know about the testing results:

A.  Interpretive Considerations for Mold Sampling

Mold is a part of the natural environment and can be found everywhere, both 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.

However, the experts agree that visible molds on surfaces within living spaces should be cleaned and removed. While non-toxic molds may not cause any health issues, they can still be quite destructive to your home. Further, many people have mold allergies and may experience some negative side effects.

B. 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 spore counts and spore counts of the identified individual mold genus are compared.

An acceptable NFE in an indoor environment may have settled spores, fungal fragments, or traces of actual growth whose quantities are reflective of a normal fungal ecology for a similar indoor environment. NFE is time and season-dependent, so these factors should be taken into consideration.

C. Statistical Significance

According to the Indoor Air Quality Association’s (IAQA) “Standard 2110: Level I Assessment”, a “significant difference” occurs when total counts of fungal spores/structures are more than 10 times the baseline amount (called a “Factor” difference).

A statistically significant difference is a result that’s not attributed to chance. So, if your results come back 10-fold or higher than the average range, then it is quite likely that fungal spores are present.

Final Considerations

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

Ultimately, you need a mold expert on your side to gather accurate samples, explain the results, and provide advice on your next steps. Here at GreenWorks, we specialize in mold testing, removal, and remediation services for homes in the New Jersey area.

Our technicians are all certified professionals who provide expert environmental advice with fair and accurate results. Reach out to us online today to connect with our team and schedule a service.


First published on: Oct 9, 2020

Updated: Dec 3, 2021

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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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