FAQs about the accuracy of air sample tests for mold contamination.

This article series offers an simple tutorial which provides information about the accuracy of and sources of errors in tests for the level of allergenic and toxic mold in residential buildings.

Accuracy & Validity of Viable and Non-Viable Indoor Fungal Spore Counts & Cultures

These questions and answers about the accuracy and thus reliability of various mold tests and mold counts were posted originally at ACCURACY OF AIR TESTS for MOLD - please review the discussion there.

Reader Question: if the indoor mold level is the same as outdoors, does that say there is no mold problem?

I just had an air quality control test done on my bathroom for mold.

They took air samples from in the bathroom and from outside. I’m told that if the [airborne mold spore] count is the same inside as it is outside there should be no mold problem.

My questions is to what degree difference is it a problem? In other words is there a rating number or cut off number that says it’s safe vs. not safe? Thanks for your reply. - J.C.

Reply: ... sparrows are flying around through the air outside at 1 sparrow per cubic foot, and bats are flying around inside your living room at 1 bat per cubic foot. On that data comparison we conclude that you don't have a bat problem inside your home. Does that make any sense at all?

JC:

While the opinion about counts you state above is not absolutely without any merit, it is basically a mistake.

The risk is that we're comparing apples and oranges - you could have an indoor count, even a "low" count of a highly toxic easily airborne mold, say Aspergillus niger spores in spore-chains (indicating a nearby mold colonization), and an outdoor count of harmless basidiomycetes that happened at that moment of testing to be at similar levels.

But the significance of these two molds is completely different. It's potentially as ridiculous as saying leaves are blowing around through the air outside at 100 oak leaves per cubic foot, and rats are running around inside your home at 100 rats per cubic foot, so probably inside you don't have a rat problem.

Does that make any sense at all?

Now it's true that very low levels of indoor airborne mold might, in general mean that the test did not find an indication of an indoor mold problem, but

• Low mold count numbers may miss a problem:
• Certain indoor particle levels in certain forms, such as chains of Aspergillus sp. spores found in indoor air, can still indicate an indoor problem even though the absolute count detected in the test was very low. Similarly a high count of a harmful indoor mold compared with a high count of a harmless outdoor mold can hardly be taken to mean there is no indoor problem.
• Enormous variability in test results:
• Because indoor and outdoor particle levels vary enormously over minutes of time and small changes in conditions (opening a window or turning on or off a fan, or even exactly where the technician placed her air sampler), a huge portion of the test accuracy in describing the indoor conditions depends on these variables.
• Hidden mold reservoirs may not be detected:
• There are plenty of other reasons for variation, hidden problems, and other conditions that mean mold or other indoor contaminant problems meriting professional cleaning will not show up on an "air test for mold"

So while a high indoor problematic mold spore count most likely means that there is a problem to be found and corrected, the opposite is not necessarily true

: a low indoor mold spore count does not promise that there is no problem, and an indoor airborne mold spore count that simply compares with the outdoor mold spore count is a leaves and rats comparison that to me makes very little sense.

There are many general mold exposure standardsthat try to talk about levels of airborne spores, but they are only very vague guidelines.

The level of indoor airborne particles varies enormously, by orders of magnitude, from minute to minute and depending on what's going on indoors.

See MOLD EXPOSURE STANDARDS for details.

So these indoor and outdoor airborne mold count comparisons and "tests", without being accompanied by

1. a thorough building inspection indoors and out (to identify likely sources of trouble or even visible mold),
2. an occupant interview (of health risks, vulnerabilities, observations, complaints), and
3. a building history (of leaks, sewer backups, construction snafus),
4. possibly some limited invasive inspection (test cuts) in areas of greatest risk of a hidden mold reservoir

... without those, a "test" is simply unreliable at best and junk science at worst.

Watch out: by no means do I suggest that every mold worry should result in such a thorough building investigation.

I can find some mold on surfaces or contents in just about any building anywhere - it is not necessarily a worry at all.

If there is mold growth on caulk or grout joints in a tiled bathroom adding up to a few square feet of moldy surface, no report nor concern for leaks into the bathroom walls, floor, ceiling, no occupant complaints, then the right response is clean off the moldy surfaces.

Question: pin prick feeling or a feeling of a fiberglass sting on our skin

(Mar 17, 2014) Anonymous said:

We have been bothered by a pin prick feeling or a feeling of a fiberglass sting on our skin, both on exposed and covered areas of the body for several months. We've had the HVAC vents cleaned, the furnace checked and cleaned.

We've been to dermatologists to rule out any medical condition.

These pricks leave no mark and do not itch once you've brushed the area where you feel the prick. They leave no mark. What do you suggest we check to find out what's been bothering us. Thank you.

Reply:

Anon

This is not a mold test accuracy problem so much as a problem of properly identifying the likely source of the complaints you describe. A number of indoor particles and even some chemical contaminants as well as health or skin problems can cause the feeling you described.

See FIBERGLASS HAZARDS - home

, and MORGELLONS SYNDROME to read about the type of complaints you describe.

Also see ITCHY FABRICS, FURNITURE

On 2018-12-01 05:20:32.341520 by Anonymous

Thank you! Unfortunately, we don't know a lot about the moisture history of the house having just purchased it from the original owners who were not very helpful or forthcoming. So we're having to do a lot of sleuthing on our own going off of small clues here and there.

The inspector, who has been very thorough, pulled insulation back in one area because there was suspicion due to a water stain on an area of the subfloor above it (though we've never seen a leak there). In any case, when she pulled the insulation back, she observed a 12" square area of dormant mold.

Based on that finding, the lab number of high (5,000) asp/pen in the basement, and my allergy to mold, she recommended a remediation that would involve pulling out all the insulation and a half wall where she is also suspicious there could be a source, though, again, no obvious water or leaks have been observed; only a few small areas of staining.

But at what point is it safe to pull stuff out and at what point should a person create a remediation setting so people and the space are protected should anything significant be found? That's my question. It seems a bit wild west to start ripping things out without being prepared to immediately address a problem should there be one. No? Thank you so much for all your help!

On 2018-12-01 by (mod) - two obvious potential reservoirs of mold

I should have explained that there are two obvious potential reservoirs of mold in the situation that you described.

One is mold in the insulation itself which may not even be visible unless an expert examines the appropriate samples or vacuum samples in the lab.

I've seen that condition when insulation is exposed to mold from other sources or when it's over a damp or wet crawl space or basement.

The other common mold Reservoir that could be hidden in a basement or crawlspace is on the wood surfaces of the joists and the subfloor above that are presently covered by insulation.

It may be appropriate to do some exploring in that area. Particularly if the inspector is convinced that the reservoir is there and nowhere else in the area.

I would certainly like to have considered the history of the space below and around the insulation before deciding to take it all out.

When possible a very effective strategy is to look at the history of the building where there has been water or moisture and based on that identify the most suspect area. That's where you explore first.

On 2018-11-30 19:47:43.710846 by Anonymous

Thank you so much for your prompt reply. Here's what seems like a catch-22: The mold inspector and remediator (separate companies, presumably no financial incentive for referring, but who can really know?)

want to pull insulation and a rear wall under sealed conditions in case they find more mold, which makes some sense since normal conditions would put the house at increased risk of spores spreading (I presume).

But they're also basing the scope on the number, which I've come to appreciate is much more complex than it appears from reading this site. In any case, pulling insulation out to further inspect seems a bit like a fishing expedition while at the same time, if there is a problem bigger than the 12" square we'd like to know and address it.

Still if no one has identified a bigger problem and more critically the source of it, that seems like a bogus approach.

Especially since every inspection we've had of the house notes no mold, extremely dry conditions, no signs of active leaks, etc. So what to do? Is it possible to hire you for a more in-depth phone consult?

On 2018-11-30 by (mod) - Because the results of air tests for mold can vary by more than 4 orders of magnitude from actual,

Anna

OPINION:

Because the results of air tests for mold can vary by more than 4 orders of magnitude from actual,

because mold culture tests are fundamentally inaccurate, failing to grow 90 % of mold genera/species

because no "mold test" is prescriptive: it does not tell us where the problem is, how big it is, what caused it, what cleanup is needed

because even if such a mold test does indicate that there is a problem you have to hire someone all over again to tell you where it is, what is to be done, doubling the cost

I would never undertake a costly "complete remediation" for mold based on a superficial and incomplete "test" or report on mold that found only one square foot of mold.

I cannot be smarter than your on-site expert as she or he should be able to see far more conditions than you can report in a text message.

But if it were my home I'd want my expert to find the mold, identify the scope, confirm that it's more than 30 sq.ft. of contiguous moldy material (that's the tipping point for bringing in an expert mold remediation company),

and then I would agree that the initial scope of mold remediation work, now properly defined, would be expanded as needed if/when the remediator, on further opening walls, floors, ceilings, or removing insulation, finds additional mold-contaminated materials.

On 2018-11-30 by Anna

An inspector did a thorough inspection of a home we purchased (inside and out), took a thorough history, conducted a detailed visual inspection, and found no evidence of mold beyond two very small (4" square) areas that looked like there has been mold in the past and made recommendations for removal and cleaning (which we did).

Shortly thereafter, after we developed a small leak under a window, we had him return to inspect the basement (again, as it was part of his original inspection).

And while there was no visible moisture below the sub-floor, after pulling back some insulation under where the window leak was on the floor above, an area of dormant mold was found (about 12" square). He then did a spore trap test in that location and another in the basement.

The results came back high for asp/pen from both locations, with the location next to where he'd pulled back the insulation the highest (5,000).

He is now recommending a full remediation of our basement.

However, it seems that collecting samples in very close proximity to a place with dormant mold that had just been disturbed was not wise as it could skew the sample since spores would naturally have been released from the disturbance. What is your perspective on this testing procedure?

And is it possible that this sloppy (in my view) practice may have introduced spores more generally into our basement so that now we couldn't do a targeted clean up if we wanted to (see next paragraph) because now we need to be concerned about where those spores landed.

The implications are significant as we try to figure out the best plan moving forward, which in my mind could range from a targeted clean up of the area in question or a full remediation.

Would it make sense to re-test without having the air disturbed in the area in question, do a remediation because it's asp/pen and suggestive of a potential larger problem, or something else?

Of note, if there is a larger problem, no further inspection was conducted to find it. It seems that would be part of the role of the remediator who would tear out all the insulation, remove wood from rear basement wall, etc.

Lots of demo and cost, which I would surely do if warranted, but concerns over how the test was conducted have me feeling skeptical of full remediation being overkill. Your help would be much appreciated.

Thank you! This site is simply amazing. What a wealth of information so generously provided.

On 2016-09-03 15:55:28.069534 by Anonymous

You should not request an "air quality test" for mold, sewage backup, bacteria, flooding, or other hazards - since an air test alone is very very unreliable and even if an air test, by luck, happened to collect and disclose a contaminant we don't know if that's the main issue

NOR does the "air test" tell us where the problem originates nor what to do about it.

If there are health and IAQ concerns where you work, an industrial hygienist who is experienced with building leaks, sewer backups, or other building problems of the sort your building has experienced would

or IMO should make a thorough visual inspection of the whole building, review its history, review occupant complaints, and study the situation with enough breadth that there is less risk of finding something but not the right thing(s) that need attention.

On 2016-08-30 18:32:20.117179 by Nakitta Brown

What is the best air quality test and mold test that you should request from your employer when you work in a that has been subject to many floods from sewage back up, water flooding, with no windows in the area very dusty conditions i

On 2016-04-12 13:07:12.514195 by (mod) -

Joe,

As you can read above, no air test for mold is accurate nor reliable, particularly when it does not assert that there is evidence of an indoor IAQ problem.

Though there are general guides to indoor mold levels in air, since some spores are harmless and others, not, it is not coherent to conclude much of anything about the indoor hazard of an indoor mold count that simply gives a number.

I'd ask for my money back if whomever I hired for this "test" didn't provide any interpretation, help, nor a visual inspection, site history, personal history, nor anything else that actually helps us 1. identify a possible problem and 2. tell us what needs to be done.

On 2016-04-12 12:58:16.534670 by Joe S.

Just had air test completed in my basement. Total spore count is just under 5000. How unhealthy is this? My anxiety over these results is pretty high.

On 2013-02-26 20:47:37.450379 by (mod) -

Kim, with all respect, tearing apart a building before there has been a competent inspection to confirm a mold reservoir and find its locations sounds like a horrible idea that risks making a mess and wasting money.

The mold inspector was being quite sensible - and ethical - to steer away from heroic measures before there is evidence to justify them.

On 2013-01-19 04:56:47.189033 by Kim C

A neighbor in the same small group of condos has high levels of mold throughout her unit. She is going to have to tear everyone of her drywall walls out. There ia a very good chance that i am going to have to as well. My guestion is, her adjacent neighbor/unit is refusing to remove their wall which is covered in mold. Is is ok to just take out her drywall and the double drywall firewall out and replace it and just leave the mold that is on the neighboring wall? And if not how does she go about making this neighbor take out the mold covered drywall. In her unit she had an air test done and was told she had no high levels, yet she had a major ongoing leak just like my frieds who now has Stachy. The mold inspector who did the air cartridge tests simply said "Do not take down you walls". Seems to me that there is a reason he said this. He also said that he would never remediate from the inside only from the outside. I have heard there is no way to get all the mold that way as the 2x4s that bunt up against the interior drywall can not be cleaned and if the drywall has mold then it needs to be removed anyway. This technique does not work for interior walls between units either. Thanks

On 2012-11-22 01:11:42.630289 by (mod) -

LA

Cleaning the air is not feasible and has absolutely nothing to do with removing a mold problem. IF there is a high indoor mold spore count the correct steps are

find the mold reservoir
remove it

On 2012-11-21 03:03:53.661949 by L.A

Hi Dan,

Well before I hired the inspector I already found mold and removed it myself with vinegar and clean up all the visible molds. But I guess because of the tenant who occupied the room didnt perform any cleaning or regular maintenance for the room and caused mold to grow. And right now I'm wondering if there's any home remediations that I can do on my own to clean the air for that specific room to decrease the spore counts.

On 2012-11-20 05:29:10.216411 by (mod) -

L.a.

Of course.

Fire the inspector who charged you for a test but didn't do the job properly, failing to tell you where the mold reservoir is located and what caused it.

You need to find the mold source, remove it, and fix the reason it occurred.

On 2012-11-19 09:57:48.719694 by L.a

I just had an IAQ test of a bedroom and outdoor and the results came back to be very high for the bed room. Is there any home remediations that I can do to reduce or get rid of the high level of mold spores ?

On 2012-08-10 21:55:39.699775 by (mod) -

Sorry Rebecca, your question and our discussion left me confused between someone describing an apartment that she thought had a mold problem - in which case the question needs to be answered by a competent person on mold - or by someone who was just doing normal household cleaning.

It is entirely appropriate for a homeowner or occupant to clean their home, including small areas of mold or mold susspect materials - in my view up to 30 sqft. without having to hire a proferssional.

On 2012-08-08 21:39:56.644057 by Rebecca Smith

Cont. With me having my apartment door and windows open open for the week prior, fans blowing, and the cleaning I had been been doing, if even the test I had done may not have been totally accurate.

But I have not been "trying" to do any kind of mold remedy myself nor do I think I even posses those skills. I have just been doing what I feel is normal clean up and repair to a place I have lived in for 5 years, and honestly hoping in some way something will dilute the smells of the combination sewage/musk/stale odor because that in itself is literally very sickening.

On 2012-08-08 21:32:05.203307 by Rebecca Smith

RE: (1 days ago) DanJoeFriedman (mod)
Well I am not actually doing a "mold clean-up" per say, but since my kiddos, dogs, and myself are moving out in just a matter of days, I am doing my best as a tenant to do some touch ups here and there. Plus, I will not teat them the same way we have been treated and mold or not, I take a great deal of pride in myself and my home, maybe that is my military mindset.

As far as me completely redoing the bathroom, their solution for years has been to patch up the crumbling walls, paint, and puddy, and since I had small parts of the wall taken for inspection, some of the baseboard was pulled out, and so much of the wall was just crumbling cracking and paint was discolored, I wanted to show them even a laymen like myself can make something shinny and new "looking" plus once again, the whole pride thing.

The leaks, water damage, toilets and sinks over flowing, mold, etc. have been an issue for a few years now, and in fact I was moved out of my last 1st floor apartment after living there for a little over 2 months because of mushrooms growing through the carpet of my master bedroom floor between the exterior wall and bed.

Recently I have made some of the issues public because of the decline of mine and my families health to even include my dogs, and while I new there was a problem with mold I was assured when I asked that the primer and paint they had originally used would take care of the problem and it wasn't until nearing the end of 2011 I got to talking with someone about how sick we have been for so long and it's just getting worse, when she said it sounded like I have a mold problem like she had dealt with before.

I didn't know anything about mold until then so I started doing research. I have since really been pushing the issue with property management and they haven't done anything, but now with us having days before we move out the are sending someone to test the air. I had paid someone come a few weeks ago to test as well, and although the tests were revealing.

On 2012-08-07 01:06:18.753304 by (mod) -

Rebecca: air quality samples can be affected by almost anything - but the Q&A will be more clear if we specify what kind of air quality testing: particulates, spore traps, gases. From your question I see you're cleaning up mold.

Testing the apartment "air" alone following a mold cleanup is frankly junk science. But it is indeed common practice.

Anyway your bleach, which is not a mold cure, won't hurt and won't much affect what's in the air. Stirring up dust, or turning fans on or off, can change the level of airborne particles by several orders of magnitude.

If your apartment had an actionable mold contamination problem that merited professional cleaning (IMHO 30 sqft or more of contiguous non-cosmetic mold), I am, frankly, baffled why you, the occupant, would be doing the cleanup. An incomplete or amateur cleanup could put the next occupant at risk along with the apartment management, owner, and yourself.

A visual inspection that addresses the location and scope of original mold contamination, physical checking of cleaned surfaces, perhaps a dust sample or two, would be technically a stronger basis for concluding that a problem has been addressed - presuming that the original mold scope of work was properly identified and removed. "Painting over mold" or "bleaching mold" are not recommended remediation procedures, though it's fine to clean, disinfect if you like, and paint or seal surfaces once they have been cleaned. And of course you probably have read that moldy drywall should be replaced, not painted.

Details are at
MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD (article link at page left)

On 2012-08-06 21:37:59.384823 by Rebecca Smith

I did look to see if I could find my answer on the internet before contacting you, but I couldn't. In your professional opinion can air quality samples be altered in any way by fresh paint and bleach? The reason I ask is because I have been cleaning all of the walls, windows, floors, under sinks, well pretty much everything because I'm getting it cleaning up to move. Plus I repaired and repainted the entire master bathroom where most of the mold was found, and all of the cracks, nails pops, etc. throughout the house. I had just received a call from management, they are sending someone on Thursday to test my apartments air. I did not know they were going to be going this because they said they already did, or I would not have fixed all this stuff. If you are not sure, do you know where I can get this information?

On 2012-06-03 16:10:35.747020 by Jan Verow

How do I know who is right? I have conflicting test results from 2 different companies? I would assume the relative humidity outside would affect the humidity level inside the house and the results of the test?

On 2012-02-29 22:15:28.440542 by Alyson

What about ERMI testing? I have had an area of prior water damage in my apartment for several years and suspect my numerous health problems may be caused by hidden mold growth. I am considering doing an ERMI test myself just to confirm my suspicion that there are high mold levels. I am planning on leaving but would like at least some information about the air I've been breathing all these years...

...

Continue reading at ACCURACY OF AIR TESTS for MOLD - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see ACCURACY OF AIR TESTS for MOLD FAQs-2 - more-recent Q&A about the accuracy of airborne mold tests

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