Mold testing compared with mold inspection: this article explains why mold testing may be very unreliable and why you may need an expert on-site inspection.

Not every mold problem merits testing and onsite expert inspection or cleanup, but where large areas of mold are present, where there are serious health concerns, or where large costs may be involved, you need an expert on site, not a "mold test". Here we explain why.

Mold or Particle Contamination Tests vs Mold Inspections - why the difference is very important

Not every mold worry merits a costly onsite investigation. But failing to hire an expert when one is needed can itself be a costly mistake.

If your ONLY concern is the identity of the mold you've already seen, and if you are confident that there is not a possible problem elsewhere on the property, you could simply send a mold sample to our lab (or to any mold lab) for determination. Instructions for an inexpensive and easy way to test mold or to screen settled dust for mold are at MOLD TEST KITS.

We emphasize that for small areas of mold contamination, generally where less than 30 square feet of contiguous mold is present, simple building cleaning and renovation procedures are all that's needed and testing is usually not appropriate. Most building mold contamination falls in this first category.

Photo: we inspected this mold home for a national insurance company after the owner had left it unattended for several months. A boiler leak had dumped hot water in the basement and soaked the entire upstairs with warm moist air for months.

At DO IT YOURSELF MOLD CLEANUP we provide suggestions for a do-it-yourself cleanup of small areas of mold.

At MOLD TEST REASONS we discuss when it is appropriate to test for mold.

A mold professional may have some neat gadgets to find or test for mold, but a true building expert knows that a thorough building inspection and an understanding of how buildings work and where they leak, as well as an understanding of mold itself, are critical in finding hidden mold problems and in specifying the cleanup work needed.

To be effective and to produce advice which is based on more than a wild guess, building investigations for mold, allergens, gases, or other indoor air quality concerns must take a broad approach to site and building examination for probable sources of moisture, bioaerosols, toxic/allergenic mold, or other allergens.

In order to have some confidence that we understand the building, how it works, where the risks and problems lie, we examine at the entire structure, inside and out, and its mechanical systems are examined as well. Partial inspections, like partial remediation, risk the cost of having to repeat the process if it was not proper and complete the first time.

In the photos above on this page, though not much mold is visible on the drywall, the presence of fungal fruiting bodies or "mushrooms" growing indoors at the wall baseboard trim tells us that this building was very wet for some time - professional inspection is needed to define the location and extent of moldy material removal and cleaning.

Reader Question: where can I buy a bariscope? I want to check for hidden mold.

Where can I get a bariscope in Toronto?

It is a boriscope.

Reply: you mean borescope. But your approach to checking for hidden mold may not be effective.

Sorry, there is no such device as bariscope. Nor a boriscope. Perhaps you are asking about a borescope such as the instrument we discuss at Hidden Mold in Wall Cavities ? If so, any professional inspection equipment supplier in Toronto or online can quickly provide the instrument.

Reader follow-up: I'm hiring a mold inspector

Thank you, an inspector is coming tomorrow at 7pm...he tried to cancel...i iinsisted as i  im leaving the unit by sunday, i settled in a human rights tribunal with the illegal landlord, for illegal profiting, they were refusing to accommodate me in regards to mold testing, public health inspector and management there, said there were no visible signs and would not make a demand for the landlord to pay as the recent agreement i had made where they would pay, hence the public health human rights claim.   

Reply: Reliance on a borescope alone for hidden mold detection is unreliable.

For hidden mold investigation, a borescope alone is inadequate. While I find the borescope useful for a limited view into tight spaces, experiments with the results of inserting the scope into a building wall or ceiling cavity compared with the improved view afforded by cutting a larger inspection opening (typically 4" x 3") has convinced me that it's worth the trouble of making the larger opening size at strategically-chosen high-risk locations.

Furthermore, making the larger wall or ceiling cavity opening makes several more reliable inspection steps possible when checking for hidden mold:

• We can inspect the cavity side of drywall in the high-risk location, checking for visible mold growth
• We can inspect and possibly vacuum-test wall or ceiling cavity insulation for mold contamination not visible to the naked eye
• We can better view signs of water intrusion or moisture accumulation as well as signs of other invasions such as by insects or rodents.

Reader Follow-Up: why can't I just scrape a surface and take it to a lab?

What if i scrape and take it to a lab;

Reply: Why you need a proper, more-reliable investigation for hidden mold or other particulate contamination

Scrape tests of surfaces risk damaging the material; for surface testing use the tape method described at MOLD TEST KITS.

But you miss my point: "hidden" mold might be suggested by the detection of certain mold material in a dust or surface sample from a building interior, but that approach alone is invalid and unreliable; absence of evidence is not evidence of absence of a problem. It may simply mean that the "test" was not properly conducted or that the sample was not collected from a location that would have given evidence.

If extensive mold contamination is visible on indoor surfaces, you do not need to hire an investigator or "mold test consultant" to prove that fact. Our photo at left shows more than 30 square feet of contiguous mold growing on a drywall-covered ceiling in a building.

However, you might need to hire an expert to determine the extent of mold remediation needed and its cause: in other words to prepare a mold remediation plan that should guide the initial efforts of a separate mold remediation or cleanup company.

But where a large, problematic hidden mold reservoir is suspected but there is not obvious visible mold in the building occupied spaces, an inspection, not just a "mold test" may be in order.

Our article series beginning at MOLD / ENVIRONMENTAL EXPERT, HIRE ? helps determine when such an expert is needed. Here I summarize the components of a more thorough, reliable inspection for hidden mold contamination.

Scope of Inspection for Hidden Mold

A competent inspection and test for hidden mold contamination requires an expert inspection of the entire structure, beginning outdoors and continuing inside. The inspector must know building science, building methods and materials, mycology, as well as the science of various inspection and test methods.

In that combination the expert can form a reasonable opinion about the building construction methods, history of leaks or floods, ventilation and moisture concerns, and thus areas of greatest risk of presence of a hidden problematic mold reservoir.

Decision to Use Invasive Inspection Methods: test cuts into building cavities

Armed with that information, limited invasive inspection, best by making modest test openings into building cavities to inspect the inner cavity surfaces and (if present) insulation, confirm the presence or absence of mold contamination in the most at-risk areas.

Reasonable Estimates of Hidden Mold Risk Level

Such an approach does not guarantee that there is not a hidden  mold problem elsewhere, but it does permit the investigator to make statements about reasonable levels of risk, extent of investigation conducted, the chances of other hidden mold reservoirs not yet found, and thus the approach permits a rational decision about how far to take the investigation.

Risk of Wasting Time, Money, Health if Relying on Inadequate Mold Investigation Methods or Tests

By a rational approach to hidden mold investigation and testing can one avoid the waste of time and money and the very high risk of incorrect results that accrue from less thoughtful and less thorough "mold tests"

Where the potential costs of an unreliable mold inspection, test, or investigation include possible health risks to building occupants and economic risks of facing a still more costly mold remediation job, relying on a simple "test" is, in my opinion, foolish.

The Usefulness of Mold Tests

This does not mean there is no place for testing, but rather that tests for mold or other environmental contaminants must be conducted using reasonable science and experience, and their results understood accordingly. 

Even  should a more general "test" for mold, say an air test, suggest that a problem is present in the building, that information, without an intelligently drawn idea of where to look further, is of little value. We  don't know much more than we did before.

Summary of Proper Mold Investigation: Six questions that must be asked and answered

In sum, any building environmental investigation procedure, to be worth its salt, or worth the fee, must provide actionable information. It must answer the questions:

1. Is there evidence of a problem that merits further attention?
2. Is there evidence of a likely hidden problem that merits further attention?
3. Where are hidden problems most likely to reside?
4. What evidence has been found in those locations to argue for or against an actionablecontamination?
5. And finally, if no evidence of mold contamination has yet been found, when and how do we reach a conclusion that it is time to stop spending time and money looking for a problem?
6. When have we found a problem, what is the extent of the problem, where is it located? what extent of cleanup is needed, and what problem causes can be identified and corrected to prevent a recurrence?

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: Moldy Rental Apartment in a Basement - allergy flare-up

My husband, 5-month old son, and I recently moved into a water-front basement apartment (about two weeks ago) and immediately noticed our allergies flair up. My husband and I are both allergic to mold, but we can't find more than small amounts on the floor boards. In the closet of our bedroom, there is a boarded up septic pump that smells terrible and might be contributing to our problem. Our landlord is not terribly concerned at the moment. What can we do to test the area? We have all developed colds and wake up each morning with terrible congestion, drainage, and headaches. - Rosi B.

Reply: Red Flags about Mold-Suspect Apartments

There are a few things an experienced investigator hears that trigger a sort of "red flag" or prejudiced expectation of trouble, including basement+apartment+waterfront. The worry-o-meter points up a bit more for "mold allergies"
and more for "septic odors".

You are describing at least two possible problem areas: mold and sewage pathogens/sewer gas. And there could be serious health risks. Notify the landlord in writing of your concerns immediately. You can hire an experienced environmental investigator (search our website for "Mold and Allergen Inspectors & Testing Consultants" for a directory that might be helpful. Discuss the inspector's experience, and the extent of actual inspection, not just "testing" before hiring someone. Tests performed without an expert inspection are not worth much.

Question: Windows as a source of mold contamination:

How can I Tell if a Window Leak Has Caused A Mold Problem in My Home?

I had energy efficient windows installed in my townhouse over a year ago. This past spring one of the master bedroom windows leaked after a rain storm because the caulking failed. The company immediately came out and re caulked the window and it hasn't leaked since. My concern is that I now have a water stain under the window on the drywall, and since I have a mold allergy, I'm wondering if there might be mold on the inside of the drywall.

I read your article on testing the dry wall but as mentioned in the article would rather not cut into it unless it's necessary. I looked at other articles but didn't see one with a picture resembling the water stain I'm concerned about. What would you recommend? By the way, this is a very helpful website. I was considering using ozone for any possible mold in my place but see from your article that's not a good idea. Thank you. - G.N.

Reply: Follow the water, estimate the risk, decide if an expert inspection is needed, don't just "test" for mold

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with mold, hidden mold, and with tracking down just how much water leaked into the building and where it went. Indeed a basic axiom in deciding the level of risk of an actionable hidden mold reservoir is to identify places where water has leaked into the building, asking how much water leaked where for how long and just where did it go in the building? Follow the water.

That said, here are some things to consider:

First, how disappointing that your new windows leaked - certainly a wet wall below a leaky window is not particularly energy efficient, and indeed it could become a mold reservoir.

Second, the risk of a mold problem that you can't see but that is significant enough to merit removal is not something I nor anyone should guess at by email with so little information. In the article above at MOLD / ENVIRONMENTAL EXPERT, HIRE ? we give some suggestions on how to decide if it's justified and appropriate to hire someone to perform a more competent mold inspection at your building. Testing alone is not reliable.

Third, I would not rely on "mold tests" alone to decide if further investigation is needed. A "mold test", especially an air test for airborne mold, performed without an expert diagnostic inspection of the building is just not reliable in cases where the result is "negative".

We have been sick since moving in to our apartment. The landlord is replacing leaky windows but we want to move out

We moved into a basement apt last nov and both scott and myself have been on and off sick ever since we moved in, we had management come to investigate the problem and so now they are going to replace the windows, my question is this, by replacing the windows, which were the main causes of mold in our apt, i know its in the carpet and in the walls, we both suffer from hiv and we want to move out of this place, how do we go about getting out of our lease without getting taken advantage of?

our lease is up oct 31 and we cant stay that long, we have already applied for a new apt in a different area and got accepted and plan to move out on sept 10th,our lease agreement states that if we break our lease we will have to pay 1 and a half times our rent which is about $1500 and we just cant do that, what advise can you give us before we go and give our notice? please advise, thank you
clay and scott

Reply: Look at more than just leaky windows when tracking down mold contamination

I would NOT assume that your windows were the main cause of a mold problem, though certainly leaky windows or lots of condensate running into walls could be significant. Often a basement apartment has a history of leaks into walls, sometimes prior floods or water entry, and thus there is a risk of larger hidden problem mold reservoirs that can be found by an expert who combines visual inspection, history taking, and strategic testing, perhaps even some careful looks into wall or ceiling cavities in highly suspect areas.

As tenants you may have trouble with the cost of a competent inspection (about as much as your rent) and with the need for invasive measures. If you've notified the landlord in writing and no one will act, and you want to move, you need to consult a real estate attorney. Typically the combination of actual credible evidence of a habitability issue that the landlord won't or can't address is enough to justify breaking a lease.

Beware: if your apt is really moldy your possessions may need to be cleaned before importing them to a new home.

Question: My mold expert passed my home after a mold test but I keep smelling mold. How do I find where the smell is coming from?

Thank you for your excellent site! I am in a quandry about mold testing & remediation. We live in a relatively new home (about 10 years). Because I suffer from allergies & sensitivities, we had this house thoroughly inspected when we purchased it 7 1/2 years ago, by both structural inspectors & an environmental inspector (for mold & radon); both inspections were passed easily, and the environmental inspector's report called our home "one of the cleanest" he had ever tested. But I am now (and for some time) smelling mold. Nobody else does, but everyone knows that my nose knows. We have had several inspections done by various professionals, and so far we have found and corrected 2 small leaks and small mold problems ... but I still smell mold.

The only possible source I can imagine is the cathedral ceiling, which we cannot inspect properly because there is no attic there. The attics on the sides of the houses have been inspected & seem clean, and the roof has been inspected and declared good, no leaks.

One friend has suggested that perhaps there is simply inadequate air circulation in the cathedral ceiling which allows some mold growth in the insulation. We have had an infrared camera inspection, and no obvious leaks/cold spots were found (but some vaguely cloudy areas that the operator could not interpret). I have called more mold inspectors, who want to do very costly sample testing. I don't see the point: I smell the mold, I want to know WHERE it is and get rid of it; I don't really care what kind it is.

So, my question: Can we simply seal the attic/ceiling to prevent air infiltration and avoid ripping out the entire ceiling of our home? If not, what can we do to reliably verify if this is the source of the smell, or where else there could possibly be mold, other that ripping out our ceiling? Thank you! (And apologies for the long & disjointed letter)

Reply: how a mold expert decides where to make a test cut to look for hidden contaminants

Lisa, if you smell mold, there is probably a mold contamination source to be found and remedied. It may be possible to home in on the problem if your "expert" really is one - someone with both training and experience in finding building mold. We use a combination of case history, occupant complaints, and a thorough visual inspection of the building for history of leaks, likely moisture problems, and similar clues to identify the "most likely" areas of hidden problems that justify further investigation - often by a small test cut into a cathedral ceiling to use your example.

Your description of your "experts" makes me wonder about the services you received: I wouldn't expect an experienced professional to "pass" or "fail" a building. Those terms are simply too much of an over simplification; most experienced inspectors speak with more caution, and will tell you whether or not they were able to find evidence of a problem that merits further investigation or not.

I would not just "seal" the ceiling as a mold "cure" without first finding out where the problem mold is, how large the mold reservoir is, and what caused it. Why?

• A leak that is causing mold in a cathedral ceiling may also wet the insulation, wasting energy and increasing heating costs and leading to structural rot and later, far more costly repairs that all could be avoided
• Openings in a ceiling, such as around light fixtures, may allow contaminants to enter the living space
• Painting over the ceiling is a "band-aid" approach that is unlikely to correct a mold odor - MVOC's are gases that may still find passage into the occupied space

So first let's find out if there is a mold problem that needs removal and find out if there is a roof leak that needs repair.

Question: for a Moldy school in Tulsa, I Have a Free Mold Kit - where do I send it?

I have a mold kit that someone gave me but it does not have an address where to send it for results. I

work in a school that I understand is infested with mold but they have yet to do anything about it. I have been in & out of doctors offices & the hospital with symptoms that are believed to be from the mold, & the only mold I am exposed to is here at my school. I have always been extremely healthy, but now suffer with asthma & allergies due to mold.

In fact, I have to go to an ENT for weekly injections for mold. I don't mind paying for the test, even though my school should be ultimately responsible. Can you help me? Please!!! - Anon., Tulsa

Reply:

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with building indoor air, with visible or hidden mold or other contaminants, and with the cause and remedy that should be understood and acted upon - not things you can decide from a mold test kit. That said, here are some things to consider:

you don't say whether your "kit" is intended to collect a physical sample on tape for direct microscopic analysis or (as more likely I guess)

if it is a mold culture plate ( a round plastic container with some media inside)

You can send your mold test kit to any mold test lab - most of them anyway - will accept it and charge you an analysis fee. But you should realize, especially as you express health concerns, that "test kits" for mold are basically unreliable when used in the absence of an expert onsite inspection, occupant interview, case history. Only about 10% of molds will grow on any culture whatsoever, so you're about 90% wrong when you open the box.

Details are at Mold Culture Plate Test Errors.

Therefore if you or others have reason for serious concern about mold and indoor air quality in your workplace, it seems to me smarter to be sure that a competent expert is engaged to help assess the situation. To avoid any appearance of conflict of interest, having given the advice in this note, that is not a service that we would provide.

Beginning

at MOLD / ENVIRONMENTAL EXPERT, HIRE ? we provide advice that can help you decide if hiring a mold expert to inspect, interview, and perhaps conduct some testing is appropriate.

Question: I had a house air test for mold and Asp/Pen was 920 and 644 and 2850. There is no visible mold. Should I be concerned?

I recently had a air quality sample done of our house. Asp/Pen outside was 920, on the first floor it was 644 and in the basement it was 2850. There are no visible signs of mold. Should I be concerned and do I need a mold remediation specialist? It's a finished basement.
thanks! - John G. 10/7/2011

Reply: If your mold inspector is not answering these questions, what was s/he paid for?

John, my best advice on deciding if you need to hire a mold investigator or mold specialist is summarized in the article above. There you'll see that we list a variety of factors one would consider in making a decision to go further or not. Depending on various factors such as occupant health risks, building complaints, visual observation of water or leak history, etc., even a small visible mold colony could prompt further investigation.

Your high indoor Pen/Asp count is roughly 3x the outdoor count (and of course the outdoor count might not even be the same mold spores as found indoors) and your basement count is highest, suggesting that if there is a substantial problem mold reservoir that's where to start looking. That alone might be enough to prompt further inquiry.

Did you ask the expert you paid to perform mold tests for an interpretation of the rest results? If not, you're not getting what you paid for.

Question: moldy basement "rafters" (ceiling joists)

I was wondering I could email you a few photos of my basement rafters (I can not figure out how to attach the photos to this comment).

The area is below my living room (no overhead water source) and this mold-like staining is on several rafters intermittently, as there are rafters between the stained ones that have no visible mold.

There has been no water intrusion and the rafters have been dry. In the room is our HVAC and other mechanicals. I have reviewed your articles and it seems like it may be the cosmetic variety that is harmless. However I do notice a moldy odor in the basement during the rainy/humid seasons.

I am getting conflicting ideas based on your articles about mold odor meaning there is definitely mold that should be dealt with and cosmetic mold. - Anon 12/26/11

Reply: guard against spending large sums on cosmetic, harmless indoor mold

Mold on basement rafters?

We would be glad to take a look at photographs that help explain a question you pose to InspectAPedia experts. Use the CONTACT links found at the top or bottom of our web pages.

While examining a photograph is never a substitute for an expert on-site inspection, and while often an expert will find important conditions that a layperson may have not noticed, photographs do provide excellent information that can often allow us to make useful comment.

Question: we have been constantly sick, my mold inspector didn't find anything, but based on 300 spore/M3 of air the inspector called for $2000. worth of remediation

I and my kids have been sick constantly for the past 4 months with respiratory issues. My husband thinks it's just because my son started preschool but I was concerned so I hired a professional to do a mold inspection and test. The inspector found no visible sources of mold, water damage, etc. He thought our house was pretty clean.

But then the air samples he took came back from the lab with around 300 count of Penicillium/Aspergillus mold spores in the bedrooms where the samples were taken. The final report called for $2000 of professional remediation cleaning of the bedrooms using HEPA vacuuming, etc from their company to solve the problem solely based on the air samples taken because the inspection otherwise found nothing.

At this point, I"m not sure what to do. I'm not sure whether I should move forward with this costly remediation when there isn't a source of mold found. I'm not sure this remediation of cleaning out the rooms with even make a difference overall.

And I'm not convinced we have a problem with an Aspergillus/Penicillium spore count of 300 in the air. If I was convinced then I would spend the money but it's a lot of money for us. I'm not sure what to do. - Felicia 5/29/2012

To clarify a bit further. The outdoor asp/pen count was 90. So the inside count was 3x the amount as outside at 300. But I did read in another inspectapedia article that clean building counts ranged from 250-600ish. I read the article above but am still not sure what to do. Thank you for your help. - Felicia

Reply: first confirm that there is a problem, second find it, third find its cause, fourth remove the problem and fix the cause

Felicia the report and advice you received sound very questionable to me; if there is a high indoor Pen/Asp count then one needs to look for and find the source of that material. Just surface cleaning of exposed areas is premature and a waste of money - it's treating the symptom without finding and fixing the cause.

An expert inspector examines the entire building, inside and out, and when there is no visible mold of consequence, but testing and case history and other observations suggest a mold problem, then s/he looks for and investigates further into the most likely locations of a hidden problem, often by looking at the building leak history or design that points to most likely locations for hidden leaks or moisture traps.

Watch out: For an article with many examples of how one might interpret various mold inspection or mold test results with different "spore counts" take a look at MOLD EXPOSURE STANDARDS. But keep in mind that very trivial changes in how a "test" is conducted can result in several orders of magnitude difference in the "count" number obtained, and worse, some tests that detect mold are detecting the mold that liked a culture not the mold that is a problem in the building.

1. Comparing indoor to outdoor mold spore counts, while a common practice, is highly unreliable as it's often comparing apples and oranges. For example outdoor Pen/Asp could be a completely different genera/species than the indoor mold, thus making their comparison irrelevant;

Also even very low spore counts can indicate an indoor mold reservoir in certain cases, such as finding Pen/Asp spores in connected spore chains.

2. Please take a further look at the article above, including the FAQs section, intended to give you some criteria to help decide when it is justified to dig further into this question for an individual building. Then let me know what questions remain.

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Continue reading at MOLD / ENVIRONMENTAL EXPERT, HIRE ? or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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