Are You Still Wasting Time & Money on Spore Trap Tests?

“Americans, on average, spend approximately 90 percent of their time indoors, where the concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations.” - EPA


Has the cold weather and covid-19 forced you to spend much of your time indoors working from home, online school, and binge-watching Disney+* and Netflix*?  If so, I think you’ll agree with me when I say maintaining healthy indoor air has never been more crucial for your health.  Unfortunately, indoor air pollution has increased due to lifestyle issues, pesticides, household cleaners, and most recently energy-efficient buildings that lack ventilation.  You probably have heard you can test your indoor air, and indeed you can. The big question is, which testing method is best?  Let’s look at the most common air testing methods used today. 

First, there is the simple home test kit.  Home test kits include a petri dish, swab, and a mold growth medium.  The directions are straightforward, and mold will typically grow inside or outside within 48 hours. Homeowners like this test for detecting unseen mold.

What we like:

  • Well, it is the least expensive way to test for mold. Home kits may be purchased at a hardware store for as little as $7. 

Here’s the problem:

  • Petri dishes are designed to grow mold and because every property has some percentage of mold spores, there is a high probability if they are heavy enough to land in the petri dish you will grow mold.  Most users found they were able to grow mold in the dish.
  • This method of testing will not tell you which spores are responsible for either the visible mold you are seeing and/or the symptoms you are experiencing. It cannot tell you if the mold is producing mycotoxins or other mold toxins.
  • When mold grows in the petri dish, the sample must be sent to a lab and can cost $40 or more for results. Well there goes our “what we like” about this test. 

The bottom line is that the results from home test kits will not tell you the source of mold and without that information you cannot know where to remediate or correct the cause of the mold.

Another commonly used test is the Environmental Relative Moldiness Index (ERMI*) Test.  This test was developed by the EPA to test water damaged buildings and evaluate levels of molds in a property. The test comes with a cartridge kit and requires a HEPA vacuum to attach the cartridge to.  ERMI utilizes samples from dust on 2’x6′ sections of carpet – the idea is that mold spores drop to the carpet and utilize a cassette on a vacuum to collect the dust samples from various carpet samples.  Once samples are collected the samples and form are mailed to a 3rd party lab for evaluation. 

What we like:

  • ERMI* can test for 36 mold species.
  • The results are assigned a number that can be compared to a national database number to determine the level of moldiness.

Here’s the problem:

  • The EPA website says this test is not for mainstream use only scientific purposes, in other words research only.
  • Clean environments will need to dust entire home to get enough dust and the test will also pick up bacteria and viruses.
  • Dirty environments like underneath a refrigerator are often sampled, and these samples may show mold, but it is not a practical result to rule that mold is the health issue. The problem or symptoms can be a result from a dust issue such as dust mites.

The bottom line is that collecting dust from a carpet, filter, or surface is not a reliable or trustworthy method to acquire an accurate sample of what is breathed into the lungs from the air. 

Note:  HERTMSI* – Health Effects Roster of Type-Specific Formers of Mycotoxins and Inflammogens is a test like ERMI.  Although it only tests for 5 mold species and like ERMI*, it collects dust samples not air samples. 

So, if dust does not make for a great sample and we need to sample the actual air, then what test method does that?

Have you heard of a spore trap test?  This testing method has been widely used to collect air samples for examining air particulates utilizing microscopic techniques.  Most spore trap products consist of a flat transparent “glass slip” with an adhesive selected media onto which particulates are collected passively by drawing an air jet, naturally or mechanically.

What we like:

  • It is designed to test the air, yes, the air!
  • It is inexpensive.
  • You can test for yourself, but you will need to send it to a lab for analysis.
  • It can capture a broad spectrum of mold spores and particulate matter from the air such as pollen, fiberglass, hair, and skin cells.
  • You can compare your indoor air to your outdoor air.

Sounds great, right?  Here’s the problem:

  • Reviewing a sample from a spore trap test has a vast opportunity for human error as it is a manual process of locating and counting the particles through a microscope.
  • Some samples received by the lab can be highly loaded with particulate matter resulting in counting and identification errors due to the amount of time needed. Even an experienced lab analyst can have counting and identification errors due to eye fatigue. 
  • Spore concentration in a building can vary seasonally, by day, by time of day, and even at varying positions and heights. These variables make it difficult to sample the air because mold spores are not uniformly distributed in the air and therefore the sample can produce skewed results.

Bottom line, this testing method has too many variables to determine accuracy; not very scientific. 

Okay, so before you get too discouraged let’s talk about an air testing method we like!

Have you tried a particle counter?  There are various particle counters to choose from depending on what type of pollutant you want to detect.   An air quality particle counter can detect airborne contaminants and can quantify particles affecting indoor air quality. 

What we like:

  • A high-quality particle counter can monitor both large particles (pollens, larger bacteria, plant spores, and dust mite feces) as well as small particles (fine dust, bacteria, mold spores, smoke, smog, and coarse dust). Certain particle counters can measure as small as .3, .5, 1.0, 2.5, 5.0, and 10 microns.
  • And yes, there is a standard to compare to! It can quickly measure the number of particulates in the air by room.  For example, for an ISO clean room or clean zone which hospitals and labs require, the counts of particle sizes for that “clean room” class cannot be exceeded when tested.  
  • A particle counter can also measure air temperature, relative humidity, and CO2 levels. These factors are important considerations for IAQ as high humidity and lower temperatures can contribute to mold growth.
  • This testing method provides immediate results, a detailed report, and is highly accurate…no lab required.

Here’s the problem:

  • Some particle counters do not measure volatile compounds which can also contaminate indoor air and they do not identify the species of mold.
  • The higher-quality devices are very expensive to purchase (over $1,500). The best way to have the test done is through professional IAQ testing company.
  • Like the spore trap, spore concentrations in a building can vary and are not uniformly distributed in the air producing skewed results. However, the nice thing about a particle counter is that it is easy to use, it can test several rooms at a time, and the test can easily be repeated at different heights and times of day.

The bottom line is that when it comes to measuring the quality of the air you breathe, a high-quality particle counter is an excellent method for comparing your air to an internationally approved standard (see  Knowing this information can be most helpful for people suffering from allergies and asthma to help determine the best time to turn on air purifiers, HEPA devices, or open windows and it can indicate if there is an issue that should be investigated further.  

A professional air testing company like Certified Indoor Environmental can test your indoor air quality with an advanced particle counter AND identify the source of the air pollution, provide solutions, and help you to improve the quality of the air you breathe.

IAQ Pt3 16×9

While it is important to know the state of your home’s air, we believe the more important question is how to improve it.  Stay tuned for Part 3, “How to Reduce the Level of Contaminants and Improve Indoor Air Quality”.

CIE | Author – Lynette Schmidt, Business Development Manager | November 12, 2020

Need your indoor air tested?

At Certified Indoor Environmental we use advanced laser particle counters that can accurately and instantly report particulate matter detected in any room that may be considered an unhealthy level.  We use the same technology that hospitals, laboratories, and engineers utilize for “clean rooms” to help determine the status of the indoor air.  We can provide a detailed report that lists findings as well as an individualized and affordable plan for remediating the problem.  We have over 800 5-star reviews!

Contact UsIAQ Tips

Certified Indoor Environmental is licensed, bonded, and insured. We support realtors, home inspectors, property owners and managers.   Our technicians are certified and trained by the IICRC (Institute of Inspection Cleaning, and Restoration Certification), the organization recognized for setting the highest standards for the cleaning and restoration industry.  Learn more about our process here.

For more information and tips to help improve your indoor air quality, including a FREE download, please visit CIE – Indoor Air Quality Testing.

#IndoorAirQuality #CIE #IAQ #Mold #Mycotoxins #Moldtesting #IAQtest


1 –, Indoor Air Quality, Importance of Indoor Air Quality

2 –, The Problem with Petri Dishes for Mold Testing

3 –, Office of Inspector General, Public May Be Making Indoor Mold Cleanup Decisions Based on EPA Tool Developed Only for Research Applications, August 22, 2013

4- Mold & Bacteria Consulting Laboratories, Understanding Spore Trap Analyses and Results

5 – Production Automation Corporation, What is a Particle Counter?, 8/18/2017

*Other names and brands may be claimed as the property of others

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