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  NOTE: May Dooley passed away in March 2024. This site will remain available as a tribute to her.

Mold Testing Options

This page covers the parts of mold and various tests to detect and measure mold. For a discussion of how mold grows, see the Health Effects page.

The following topics are on this page:


Microparticles (DNA level of detection)

Other testing modalities


Air testing: Spore trap

Search on-line for "DIY air testing." A pump should be included for the air test. Avoid gravity plates (see below).

Description: With spore trap air testing, a given volume of air is sucked in by a pump into a small plastic canister and impacts on a sticky surface inside the canister. The canister is sent to a lab. Mold spores on the sticky surface will be counted by a lab technician using a microscope.

The types and numbers of spores are listed in the report. The baseline measurement is spores/cubic meter of air sampled. For example, if three spherical Aspergillus/Penicillium-like spores are counted on a portion of the sticky surface and one tenth of a cubic meter was drawn in by the pump, then the number of Aspergillus/Penicillium-like spores would be three times ten, or 30 spores per cubic meter.

There are no official standards for what is an acceptable number. The inspector probably would be happy with 30 Asp/Pen-like spores per cubic meter, but what if there was a higher level? Any elevation of Aspergillus/Penicillium-like spores raises the "why?" question.

Advantages of spore trap testing:

Disadvantages of spore trap testing:

You may have heard that air testing is a waste of money and can miss finding mold. This can be true, but nevertheless I find air testing essential, along with tape testing of surfaces. I would not be comfortable with just doing one spore trap test per floor of the house without supplementing that with surface sampling and a microscope.

Spore trap testing is recommended, both in pre-purchase inspections and post-remediation inspections, where having a report from an independent third party is needed. This way, if negotiations are warranted with the seller or if more cleaning is needed by a remediation company, the lab has confirmed it.

Spore traps are typically used in post-remediation testing.

Here’s what should happen with post-testing, but often doesn’t:

The negative air machine (a commercial air filter that exhausts to the outside) is turned off 24-48 hours before the inspector arrives. The inspector positions the collector either on a tripod or near the floor. Dust is stirred up. The sample is taken.

If the lab report shows the levels of Aspergillus/Penicillium-like spores to be very low, I know the remediator has done a good job cleaning. (Numbers may be a little higher in an unfinished area, such as a crawlspace.)

A visual examination is also part of the inspection, as well as a check to make sure sufficient demolition has been done, and that surfaces have been encapsulated. A company that cleans the tops of cross-supports between ceiling joists likely is a company that teaches workers to pay attention to details.

Instead of the above steps, the post-remediation inspector typically does passive testing. Here is the scenario:

The remediator and the inspector should be working toward the same goal: to deliver a mold-free area to the homeowner. Both have a part to play toward this goal. The inspector should not be out to play “got-cha,” but rather to add to a good remediation job that may need a little fine tuning (hopefully, it is not more than that).

Remediation can be a costly proposition. The homeowner anticipates that after spending all that money, mold will be gone. Too often, alas, this is not the case.

Think about these potential scenarios prior to signing a contract with a remediation firm:

We’ll say more about choosing and working with remediators later, but let’s proceed to the next testing modality.

Air testing: Culture plate   top

The set-up is similar to spore trap testing, only instead of the spores impacting on a sticky surface, they impact on nutrient material, called "media," in a Petri dish, also called a "plate." The exposed plates are shipped to a laboratory, where they are placed in an incubator. If there are viable, culturable spores (live spores that like the lunch that is served) that have impacted on the nutrient media (typically a mix of malt and agar from seaweed), they will start to grow, becoming visible as colonies in a few days.

It takes about a week or more before a technician can study the colonies. She would use a microscope for that study, probably touching a tape to a colony and then putting a drop of stain on the slide before positioning the tape on the slide. The next step is to identify the mold under the microscope. A report is then issued with the kinds and numbers of mold colonies.

This is my favorite type of air testing, because, even though numbers might be lower than with spore trap testing, I can study the colonies and determine if they are Aspergillus or Penicillium or other fungi. ("Fungi" is a synonym for mold, as is "mildew.")

That is, I am able to study the plates in my home office, taking precautions for my safety, because, as I said earlier, some species of mold can grow in human tissue or, at the least, cause harm in other ways. The mold is grown in an incubator in the sunroom, which is separated from the main house, because I don’t want to be breathing in mold gases as the colonies grow.

Advantages of culture plate air sampling:

Let's clear up a common misconception among mold inspectors and remediators, that is, that inside levels of mold, particularly of Aspergillus/Penicillium-like spores, should be compared with outside levels. If the levels outside are higher than inside, you’re supposedly good.

Not so fast. Since there are over 400 species of Aspergillus and Penicillium, what species is the inspector talking about? If Aspergillus versicolor is in outside air and Aspergillus niger is in inside air, what do they have to do with each other? Nothing.

At least with culture plate sampling, you can send the sample to a lab for species identification. With spore trap testing, since you cannot learn the species from looking at spherical spores, comparing inside and outside levels may be irrelevant.

So why do I include an outside sample in my reports? Mostly because I don’t want the credibility of the report damaged if someone reads the report who believes the outside/inside comparison is important. And sometimes there is a tidbit of interesting information in the outside sample(s), such as finding higher levels of – say – Penicillium when the house is surrounded by vegetation.

Disadvantages of culture plate impact air sampling:

Air testing: gravity plate   top

Petri dishes are sold on-line and in various home supply stores for home mold testing. They are called "gravity plates," because you leave the plate open for an hour or more where you want to sample, then cap the plate and send it to a lab with your check or keep it home and see what grows.

Gravity plates are culture plates, such as I use on-site, but the difference is gravity pulling spores into the plate versus the much more accurate air pump drawling in air with spores in it. Mold levels with gravity plates will likely be much lower than with culture plate sampling with a pump. Aspergillus and Penicillium spores can remain airborne for hours. They may still be floating above when the cap is re-positioned on the gravity plate.



Surface testing: sticky tape or swab   top

A tape (or swab) is touched to what looks like visible mold. The sample is sent to a microbiological laboratory for examination by a lab technician or to an in-house service providing a report for your information only.

Some labs provide mold counts, while others just indicate the presence of certain molds. The latter is not very useful. It’s nice to know if we’re talking about one spore or 100 spores, wouldn’t you think? If 100, mold growth is present; if one spore, maybe the spore is random and floated in from somewhere else.



A story: A homeowner called me over a period of a few months to discuss using a microscope on-site. He had a 2-year-old house, couldn’t live in it due to mold sensitivities, and had spent thousands on an industrial hygienist inspection where no mold was detected in samples from the attic to the basement. Finally, he bit the bullet, and we scheduled a visit.

I set up the microscope on his picnic table, so he could see what I was seeing under it. Over 100 samples were taken, and mold was found in four locations, including Aspergillus covering the whole ceiling of the unfinished basement. How did the hygienist miss that? It was easy. For whatever reason, the mold wasn’t giving off spores, so the spores didn’t show up in air samples, and the ceiling looked perfectly clean.

Aspergillus was also found on pressed wood shelves, and Stachybotrys was found on wood flooring under two potted plants that had been overwatered. At the end of the day, the homeowner shook my hand and said that he felt he got his money’s worth. That’s what an on-site microscope can do.

Surface Testing Comments

Tape testing is my chief form of testing. I’m looking for sources of growth, whether visible or not, and tapes provide most of the answers.

How can I take 20-30 tape samples (also called "tape-lifts") at the average house and not incur all those lab fees? Working with a microscope means I can do my own in-house analysis and provide photos of the mold seen under the microscope as photo-documentation in the final report.

Because I have many years experience in learning where mold likes to hang out in homes, I don’t sample only what is visible but also the at-risk places. Because I am able to study tapes in-house, I can sample furniture and other contents as well as building surfaces.

But what to do if you don’t have a microscope?

Some of my clients have bought their own microscopes and now can find their own answers to whether something is or isn’t mold. Click for information on Buying a Microscope LINK***** and Using a Microscope. LINK*****

Another option is to take your own tape samples (See the Tape Testing Instructions LINK*****). You may send the tapes to my service for analysis for a modest fee (1 tape for $15, 3 tapes for $25, 8 tapes for $50, 20 tapes for $100, after the first 20 tapes, $4/each), or send the tapes off to one of the mold testing services on-line.

As long as you take the samples, the report won’t hold up in court. If you need official documentation, bring in a local inspector. Of course, you could do preliminary samples, and then tell the inspector where to do tape samples, i.e., perhaps where mold is present but not visible to the naked eye.

Let’s say you need a mold inspection done and there is no inspector around who uses a microscope. In that case, you might combine testing modalities. The inspector could do the (preferably aggressive) spore trap air samples, while you fill in the gaps with tape samples. I’ve had buyers who have had a mold inspection done with a local inspector but also sent me tape samples. Others have just sent tape samples.

Testing a central air conditioning system, or a forced warm air heating system   top

Significant fungal contamination of the AC unit and ductwork can be missed by both tape-testing and air sampling. Inspectors may open the heating or AC units to take a look inside, but there is an easier way to get some clues as to what might be going on in the system. Here’s where I recommend - a lab test.

Joe Spurgeon, Ph D (www.expertonmold.com), arranged with Assured Bio Laboratories in Tennessee (866-547-1727), for samples to be sent to them for DNA-level analysis. They will work directly with the homeowner, as well. Dr. Joe ran a statistical analysis on 93 houses where he had inspected and gathered data. His charts help us to interpret test results.

However, the charts may not even be necessary. Are the numbers in the report high? You may need cleaning of the whole system. Are Chaetomium, Trichoderma, or Stachybotrys present in elevated numbers? Since these three molds require more water than Cladosporium, Aspergillus, and Penicillium, there may be an accumulation of water deeper in the system where conventional duct cleaning doesn’t reach. It is possible that the Freon would have to be drained and the AC coils removed to access those hidden areas, but they could be the main reservoir for the mold. It would be a shame to spend money to have the system cleaned and to still have mold.

Actually, if levels of mold other than the three with more moisture needs are also high, draining the Freon may also be advised.

What could cause accumulation of water deeper in the system?

  1. A drainage pan may be improperly sloped to allow for condensate drainage and there have been overflows. One conference presenter said it was a "hit or miss" operation for a technician to properly slope drainage pans;

  2. Some sort of leak may be associated with the AC component;

  3. An attached humidifier may be, or may have been, in operation. A basic rule is to keep moisture from ductwork, don’t add it;

  4. The AC unit may be oversized. Bigger is not always better.

Tip: Many serial numbers have a multiple of "12" in the number. If 12 stands for 1 ton, and 1 ton covers around 1,000 square feet, you may be able to figure out if the unit is oversized. Let’s say your home is 2,400 square feet, so you would need a 2T, or 24 in the serial number. If, instead of 24, there is a "36" in the serial number, you may have an oversized unit. A 36 would be for a house of 3,600 square feet. Oversized units typically do not remove enough moisture from the air.

Technically, this type of testing is known as Mold-Specific Quantitative Polymerase Chain Reaction (MSQPCR, or PCR for short). PCR is very sensitive. Let’s say a spore dries out and breaks into 25 little fragments. These count for 25 on the PCR test. Because AC systems are not sterile environments, expect some large numbers, a magnitude larger than spore trap or culture plate sampling delivers. This type of testing gives you a better clue as to what is going on deep in the system than either a visual check or air or tape testing can do.

I would recommend getting the CAP-15 test ($145) with Assured Bio Labs. This gives you 15 of the most common species associated with water damage and dampness. You would need to do one swab for each zone, i.e., each AC unit. "CAP" stands for three of the most common molds: Cladosporium, Aureobasidium, and Penicillium.

How to sample:

  1. Call Assured Bio Lab and order 1 swab for each AC unit for central air.
    (You needn’t do this test on a window unit. YouTube has videos on cleaning window units.)

  2. Decide which supply vent covers you will sample. The cool air comes out the supply vent into the room. Avoid bathroom and kitchen supply vents and vents that are under windows that are often opened.

  3. Avoid vents that have dark discoloration on them. This discoloration could be due to Cladosporium mold, which may just be a localized growth due to condensation and not reflective of what is deeper in the system. Cleaning off Cladosporium is a homeowner's maintenance job.

  4. Take the swab and press the cotton end down on a slit in the supply vent cover as you slowly move the swab back and forth on one slit after another until you have visible dust on the swab. Think of where dust would stick as it comes through the ductwork into the room. It’s better to have too much dust than too little on the swab, but pick off the fuzz.

  5. Bear in mind that there are many variables with taking a swab sample on the supply vent cover, such as:
    • How often the vent covers are cleaned;
    • How much area is sampled;
    • How much the dust weighs on the swab (not possible to measure);
    • When the system was last cleaned, and if vent covers were thoroughly cleaned or just wiped off;
    • How old the system is;
    • Whether there is mold growing on the cover due to condensation.

Advantages of PCR testing:

Disadvantages of PCR testing:

Comments on PCR testing

If elevated numbers of Chaetomium, Stachybotrys, or Trichoderma are present, you will know that they point to some accumulation of water that should be investigated.

If levels of various species are significantly elevated, then a decision will have to be made about what to do about the AC system. I say "AC" more so than heat, because moisture is associated with the AC coils, where condensation takes place, rather than with a forced warm air heating system.

--If the system is old, it may be a good time to replace it. If ductwork is metal, it can be cleaned. If ductwork is flexduct and there is significant contamination, the flexduct cannot be adequately cleaned and should be replaced.

If you need to have the unit cleaned, be aware that conventional duct cleaning services, even assuming they are professional enough to include cleaning the rest of the system in addition to the ductwork, will not be able to access areas behind and below the coils.

Freon from the coils may have to be drained out by your HVAC (heating, ventilation, and air conditioning) contractor and the coils removed to permit access to what might turn out to be the moldiest areas. These steps alone can be costly.

--I understand that some models of AC have a triangular piece of sheet metal on the back that can be removed for access behind and under the coils. If that were temporarily removed, then Freon may not have to be drained and the coils taken out.

In addition to accessing these hidden areas, careful cleaning of other parts of the system is needed. Cleaning guidelines/standards can be found at www.nadca.com, the website of the National Air Duct Cleaners Association – theoretically at least. I had to call for a set to be emailed to me after the link didn’t work.

If you interview any of their membership, be aware that not all members of this professional association include all the points in the standards. As one duct cleaner explained to me, "If I follow everything in the checklist, I have to charge more because the cleaning takes longer; my estimate is higher than the next guy's, and I lose the job."

Interestingly, there used to be a Residential tab at the NADCA website, with a checklist for cleaning. That has disappeared.

If your system is heavily contaminated, which is confirmed by the high numbers in the lab report, you might consider mold remediation rather than cleaning. Many, if not most, duct cleaning companies would not accept such a job.

Remediation involves much more tedious work, including making access holes in horizontal ductwork for hand-wiping. You would have to hire a remediation company also certified for HVAC work, to my knowledge. The cost may be close to the cost of replacement, so replacement may make more sense.

At one house, the homeowners sealed off the ductwork and changed to mini-splits. These units need to be kept clean so that mold doesn’t grow into the coils. If mold gets to the rear of the coils, this area may not be accessible, not even to duct cleaners.

ERMI/HERTMSI-2 Testing   top

Description: ERMI (Environmental Relative Moldiness Index) was developed years back with EPA funding to study levels of mold particulates on a DNA level (the same PCR testing we discussed for AC swab testing). A vacuum cleaner was used to collect dust sample from a square meter at old carpeting in an effort to answer the question of whether there might be a link between old carpeting and development of asthma in children. 36 species were found in the carpeting included in the study. HERTSMI-2 testing is a shortened version of ERMI testing, looking at only five species. Both tests deliver a score theoretically relating to how moldy the house is.

Since then, ERMI has been adapted by inspectors, doctors, and consumers for dust analysis. Important decisions may rest on the ERMI score, such as the following:

ERMI Advantages

ERMI Disadvantages

I rarely do an ERMI test, and then only at the client’s request, because I already know the house is lived in and the test will show some "issues." I know that ERMI is not going to tell me where the mold is, anyway, so what have I gained?

And if the response to that is, well, "issues" result in inflammagens all over the place, and so the $50,000 remediation is warranted, then I ask, "How long will the remediation results last?" and the answer to that is, until the door is opened and mold particulates start to blow in once again.

I am simplifying here, of course. There are exceptions. What if an incompetent remediator or untrained family member tore apart walls with Stachybotrys in them? Having Stachybotrys particulates all over the house is not to be taken lightly.

Besides the above, there are still more concerns with ERMI testing

Test results won’t stand up in court. The EPA has a disclaimer on its website stating that they do not support the use of ERMI testing residentially.

The ERMI testing protocol has to do with vacuum cleaner dust sampling from a square meter of carpeting. Any other type of sample collection is not in line with the ERMI protocol.

Questions have risen about the credibility of the scoring method, including a serious challenge to the computation and use of the score, i.e., that the score may well be inaccurate and lack validity.

There are also questions about the placement of some of the species on the list, such as Alternaria being placed in the outside mold column. Alternaria is a significant mold for provoking asthmatic symptoms, yet if Alternaria is present in high levels, the ERMI score technically goes down, not up, when the reverse should be happening.

Dr. Joe Spurgeon, www.expertonmold.com, gave a presentation on ERMI, the shortened version HERTSMI-2, and mycotoxin testing (next topic below) at the Healthy Buildings Summit, 2019. If you would like a copy of that presentation, just send me an email to request it. Dr. Joe has given permission for its dissemination.

In this presentation, of the HERTSMI-2 score, Dr. Joe remarked, "There is no rational basis for the score."

At least with the CAP-15 test from Assured Bio Labs, if levels from dust on a supply vent are high, you know where the mold is coming from, that is, deeper in the AC system. Plus, there is no score that could be misleading.

Much mold may be missed with ERMI. ERMI doesn’t pick up on hidden mold, such as behind walls, above ceilings, and in and below sink cabinets. Not all common species are listed for PCR testing. For example, at some houses Aspergillus tereus is a concern, but the ERMI test would miss this, because this particular mold is not included in the list of 36 species.

One of my clients bought a luxury apartment, and her home inspector did spore trap testing as well as ERMI testing. She later told me that he advised her to buy the apartment, saying with confidence that "it didn’t get any better than this."

So she bought the apartment, started having mold reactions, and noticed that one wall bordering a bathroom/closet was bowed out. She called me in, I slid a putty knife with tape wrapped around it under the base molding at the bulging wall, put the tape under the microscope, and there sat Stachybotrys. What followed was a huge and complicated remediation job, with her out of the apartment for close to a year … but there had been good ERMI results.

Mycotoxin Testing   top

First, what are mycotoxins? “Myco” refers to mold, so mycotoxins are toxins given off by mold, under certain conditions. Mycotoxins are chemicals and not volatile, that is, they do not become airborne. Of course, if a remediation job is botched and if mycotoxins are present, say in a wall cavity, they could be spread hither and yon.

What is the purpose of mycotoxins? At least one function would be survival. For example, Stachybotrys may attach potent mycotoxins, trichothecenes, to its spores as a survival mechanism…to protect the spores from predators.

There are hundreds of types of mycotoxins, but generally, only a few are reported on. Most mycotoxin research comes from the food industry, so I would guess that the short list most talked about with mold illness may also be some of the main mycotoxins found in food, as well as in water damaged buildings.

In the US, reportedly 12 ppm (parts per million) of mycotoxins are permissible in food. In Europe, standards are more stringent. One colleague went to a European mycotoxin conference and told me that the conference was all about veterinary science, i.e., animal food, without even a mention of mycotoxins in residences.

How did concerns about mycotoxins in food spread to concerns about mycotoxins in the environment? Real Time Lab, has been an advocate for studying this link for a long time.

The hypothesis appears to be that mold in the home gives off mycotoxins which then become airborne and are inhaled by individuals and then get from the lungs through whatever path into the digestive system and out through the kidneys? I am unclear about this and will leave better explanation to the doctors and to Real Time Lab.

From an indoor air quality stance, this subject is perplexing, because mycotoxins are not known to be volatile. Mold gases (MVOCs, or volatile organic compounds produced by mold) are volatile, not mycotoxins. However, this discussion is above my pay grade, so let’s proceed with talking about who offers mycotoxin testing.

How are mycotoxins in the body studied? There is a urine test available from Great Plains Lab, and from Real Time Lab (www.realtimelab.com).

How are mycotoxins in the home studied? Dust samples may be submitted to Envirobiomics, www.envirobiomics, and to Real Time Lab for their mycotoxin panels (or also in the EMMA test at Real Time Lab).

I have no expertise in know how the different offerings, prices, credibility, methodology, or credentials of the labs compare.

“Presence,” as Dr. Joe Spurgeon reminds us, “does not equate with exposure.” At one indoor air quality conference, a presenter joked that if you want to be exposed to mycotoxins, go lick the wall.

One of my clients sampled dust from inside a very contaminated AC system before it was removed, with a second sample taken for room dust. A low level of mycotoxin was found in the AC ductwork and none in the room dust sample.

Ochratoxin A

When I did some reading on the website of www.iseai.org (International Society for Environmentally Acquired Illness), one doctor noted that about 80% of her CIRS (Chronic Inflammatory Response Syndrome) patients with mold illness, tested for elevated ochratoxin A. Another doctor commented that close to 100% of his CIRS patients tested positive for ochratoxin A. This caught my attention. Ochratoxin A would be a good mycotoxin to keep an eye on.

From the internet, I learned that Aspergillus ochraceus is a common source of ochratoxin A, so I added it into the CAP 14, now CAP 15, test that I do at an AC supply vent (Assured Bio Labs). So far, I haven’t seen many samples come back positive for ochratoxin A.

From Wikipedia: Aspergillus ochraceus is a mold species in the genus Aspergillus known to produce the toxin ochratoxin A, one of the most abundant food-contaminating mycotoxins, and citrinin.)

A few of my clients, who had high levels of ochratoxin A in their urine samples, wanted to rule out their homes as sources. They took dust samples from multiple areas of their home and other dust samples from each of the air conditioning zones. Samples were submitted to Real Time Labs for laboratory analysis, but all reports came back negative for ochratoxin.

(To my knowledge, no lab currently offers the choice to test for just one mycotoxin. You have to pay for the whole panel.)

These findings caused me to address the following question to Dr. Joe Spurgeon: “Wouldn’t it make sense for a physician to put the patient on a diet low in known food sources of ochratoxin A for week or two before submitting a urine sample? That way, if ochratoxin A were still high in the urine, there would be a better chance that the mycotoxins would be coming from the environment.” Dr. Joe responded: “That would be futile. Ochratoxin A is in so many foods.”

Mycotoxin Comments

One doctor remarked to me, “I don’t know if mycotoxins are causative of illness, but as levels go down, my people feel better.” There is much we don’t know, and maybe it makes sense for patients to have a detoxing protocol, whether or not urine testing is done for mycotoxins. But even that may not be so simple. A health care professional would know to check the status of the liver and kidneys before starting detoxing.

One practitioner told a patient to take chlorophyllin 10 minutes prior to eating to help flush out mycotoxins from the food. This reportedly proved helpful.

As indicated above, research suggests that food is much more common a reason for elevations in mycotoxins than is the environment. Dr. Joe has a short paper on this subject (8 pages, July 2016). I then interviewed him about that paper.

Mycotoxins may be produced by mold in the body, such as from sinus infections or systemic candida.

A positive urine test for mycotoxins may mean little more than that the body is doing what it should be doing, i.e., getting rid of mycotoxins from food.

Maybe some people, whose bodies don’t discharge toxins as easily as the average person, need to be on a detoxification protocol. Perhaps they have had a buildup of stored mycotoxins over the years.

Stachybotrys, the toxigenic black mold (toxigenic means capable of producing toxins), seems almost in a class by itself (along with Trichoderma). I have had clients where improper remediation jobs, sometimes a do-it-yourself job by a family member, appear to have released some sort of particulates, possibly mycotoxins, relating to this black mold. These sensitive individuals sometimes have to leave the premises for good, describing their reaction as a “burning sensation in the lungs,” and other symptoms.

MVOC testing   top

Wouldn’t it be nice to have a simple test to show if mold gases (volatile organic compounds produced by mold) were present? Then you would know if there is or isn’t mold growth somewhere in the house.

Well, there is no such simple test.

The under-rated contaminant:

In my experience, both with clients and personally, some of the worst reactions seem to come from exposure to mold gases – yet the medical discussions relate to microparticles and mycotoxins, not to gases. Gases would not be picked up in either microparticle (ERMI) or mycotoxin testing. Gases come mostly from hidden mold, and both these tests miss hidden mold.

So no, I haven’t done MVOC testing in a long time. But here is a story from the last time I did MVOC testing.

The question arose about the potential for mold growth in wall cavities. The homeowner had several youngsters with Lyme disease and needed to make a decision about whether to stay in the house or move.

They had already done extensive basement gutting and remediation (incidentally, the ERMI test done upstairs missed the moldy basement).

So, I did MVOC sampling at about 4 wall and ceiling cavity areas and in several rooms. The cost of the 3-hour tests (each split between two locations) was $2,000. As I recall, the report gave a list of about 15 chemicals that are known to come from mold and not building materials. Every test was positive for about 9 of the 15, with none found in the outside control sample. More significantly, there was no pattern to the results … nothing that pointed at wall, ceiling, or room areas as the culprit.

Now what? What did we learn? I called the lab technician and conveyed that the homeowner and I were wondering what had been gained and if the testing was a waste of money. "To the contrary," he said. "You know there is a mold concern, because every test was positive for the 9 chemicals."

"So what does the homeowner do now, gut the house?" I asked him.

"Oh no," he responded. "Now you start making test holes in walls to see what is going on in the cavities."

When the homeowner heard this, she pulled the plug. "We’re not going to gut the house, and we don’t want a disclosure issue if we sell. Let’s go the positive pressure route."

And that was what they did. They had fresh air brought in, filtered and dehumidified, and delivered to ductwork. Whenever the unit was running, fresh air was coming out of every vent. With more air in the house than outside, every time an exterior door was opened, stale air (along with mold gases) was being pushed out. This concept is known as "pressurized dehumidification" and is recommended for a healthy home. See the Ventilation discussion.

- - - - - - - - - -

Well, we’ve had a session going through common testing modalities, haven’t we? Let’s move on to the subject of Mold Remediation. Or, back to the Mold Topic Index.

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