Airborne mold spore count report interpretation:
This article discusses the possible significance of different levels of indoor airborne mold spore counts and mold test reports. Here we define the acceptable level of mold in buildings following mold testing or post-cleanup mold clearance tests in buildings.
Using real-world examples we describe different mold test reports, mold counts or levels in air, and we explain what those counts mean. We discuss how to use mold inspections and mold test results to decide if there is a mold problem in a building and how to decide "what to do next".
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This article is part of our series: the Mold Action Guide which provides an easy to understand step-by-step guide for dealing with toxic or allergenic indoor mold and other indoor contaminants: what to do about mold "mildew," moisture, in your house or office, building-related illness, involving your physician, treatment, sick building investigators, reduction of irritants, and special products to help clean buildings and air.
Our page top photo shows that at this mold cleanup job the crew substituted "spray it all" for sweeping and vacuuming up demolition debris. This was not a great practice.
At left is an example of sampling for outdoor airborne particle levels during an
AIR QUALITY STUDY San Miguel de Allende
Extensive, in-depth articles about mold and other indoor air quality concerns are organized at our Mold Information Center.
A common mold remediation clearance test plan specifies that the indoor mold level or spore counts should be no more than 50% of the outdoor level. This approach can generate nonsense, particularly in mold sampling reports I've reviewed in which the genera and species of the indoor mold spores were completely different from the outdoor mold spores. For example an outdoor "Pen/Asp" spore count of 1000 spores/M3 of air might be compared with an indoor "Pen/Asp" spore count of 500 spores/M3 of air.
But often the outdoor "Penicillium/Aspergillus" spores are not the same species as the indoor species, making such count comparisons completely meaningless. Worse, some labs include small basidiospores in their "Pen/Asp" count since often many small amerospores (small round featureless mold spores) like certain Penicillium spores and certain Basidiomycetes are difficult or even impossible to differentiate microscopically. If the indoor and outdoor Penicillium or "Pen/Asp" spores are different species from one another, you are evaluating the effectiveness of a mold remediation project by comparing "apples and oranges."
It is important therefore to look qualitatively as well as quantitatively at indoor mold spores after a mold remediation project. If there is a high level of indoor spores of the same genera (and species) as the problem-mold which was originally identified then the cleanup may have been incomplete, regardless of "outdoor spore count comparisons.
A common example of incomplete work in which we find problem-levels of Penicillium or Aspergillus after a mold remediation is when mold-infected fiberglass insulation has not been removed because it "looked clean" to the naked eye of the mold cleanup crew. A simple vacuum sample of that material can indicate whether or not the insulation needs to be removed.
After a mold remediation? It depends partly on site conditions. In a sealed room where moldy debris has been removed, testing immediately may disclose an abnormally high level of indoor problem mold which has remained airborne even though the cleaning has removed all of the original mold reservoir. In that case some additional surface cleaning and fresh air exchange may be all that's needed.
Mold counts versus mold Species: Even more questionable is the use of "generic" airborne mold spore counts without further attention to genera and species. A count of 200 Stachybotrys chartarum mold spores/M3 of air would be unusually high as this mold is not normally airborne. I'd be worried about where those spores came from. Conversely, a count of 200 Aspergillus sp. spores/M3 of air in the same circumstances might be considered very "clean".
What indoor mold spore level is considered "contaminated" then depends in part on what mold genera or genera and species have been identified. But if the indoor mold count in spores/M3 (mold spores per cubic meter) of air is high enough, we may decide that more investigation or cleaning is needed regardless. While there is no well-established quantitative standard for fungal spores on surfaces or in air, mold contamination is considered present in a building when the total mold spore concentration per cubic meter of air is above 10,000. (Baxter, ETS).
Acceptable levels for individual mold species vary since species toxicity varies widely as does spore size, weight, and other features which affect risk to building occupants.
Penicillium/Aspergillus spores in air or on surfaces: There is no official standard for acceptable mold spore levels. To create such a guide would require standards for each of possibly thousands of genera/species and conditions. However “clean” residential buildings are typically 230/m3 +630/-230. Buildings with evidence of flooding are typically much higher: 2200/m3 and mold-damaged buildings are typically extremely high in comparison: 36,000/m3. I usually find only trace levels of Pen/Asp indoors, so higher counts make further investigation a reasonable course of action, particularly where occupants may be at extra risk due to fragile health.
Some writers also warn that mold labs have reliability problems. We agree that two experts counting the same slide will not provide precisely the same counts. Our lab participates in a "round robin" quality assurance program in which a group of expert mold sample processing labs around the country "count" spores on the very same slide (we mail it around). We compare our count results as a method for checking on and refining our procedures.
While counts vary among labs, it is unusual for counts by expert labs following the same (agreed-on) count procedures to vary by as much as one order of magnitude. If the mold sample processing lab is actually using an expert to process the samples (rather high-volume part-time minimally-educated workers), then the variability in lab results is very much less than the variation in mold sample results caused by variations in sampling conditions I discussed below at "Mold Sampling Conditions Cause Wide Variation in Results".
The presence of toxic or allergenic mold as a dominant particle in any sample (surface or air) is usually a cause for further investigation or remediation. The presence of incidental occurrences of toxic or allergenic material in surface samples requires interpretation in light of other building conditions, type of particle (spore chains), and other factors.
Since only a small percentage of all molds (perhaps 10%) will grow in any culture at all under any condition, using a culture to screen for problematic mold is a questionable practice. There are uses for mold cultures but we question their application for building screening.
The mold level target is never zero except in special applications such as medical and drug facilities which operate in a "clean room" environment where no stray particles are permitted. Mold is a natural ingredient in outdoor air most of the time. We do not want to find higher indoor mold levels than outdoor, and we do not want to find high levels of problematic mold spores indoors.
Warning: interpret all quantitative mold clearance test data with caution, particularly air samples. Individual samples of airborne mold (or any other airborne particles in a building) show tremendous variation from minute to minute, usually by many orders of magnitude, making "ok" mold clearance sampling test results a thing to view with care.
If the mold remediation clearance investigator did not document the sampling method, including where, when, and under what conditions a sample was collected, interpretation of sample results can be tenuous. We re building fans on or off? Were windows open or shut? Was work going on in the area? How long after completion of the mold remediation project did the investigator wait before testing?
Turning on a ceiling fan in a room can increase the airborne particle level by a factor of 1000! In situations of particular risk (such as sensitive occupants) or ambiguously-conducted post mold remediation testing, additional or periodic testing should be considered.
These FAQs contain comments on the significance of indoor mold level reports for all different counts, levels, and genera/species of indoor airborne and dust or surface or vacuum tests for mold contamination: what do these mold numbers and mold reports mean: how to interpret mold test reports.
Editor's note: we have arranged the questions and answers immediately below roughly in order of the level of indoor mold spore counts that were reported by the reader or their "mold test" person.
Had testing done in a home where the occupant developed lung cancer. Would high levels of the spores basidiospores and pen/asp group be a contributing factor? - Cyndi, 6/21/2012
You have not defined "high levels" of mold, nor whether you meant high levels in air or on surfaces. And if in air, there are many variables that can increase or decrease the actual airborne particle levels, and thus human exposure, by orders of magnitude, such as fans on or off, windows open or shut, active or still conditions in the building and more.
To prove that a specific mold exposure caused a specific illness is difficult enough that it's rarely attempted; people, their individual health sensitivities, lifetime exposures, genetics, and other variables are wide in extent. Burge cited at least 4 tests that would have to be met - and that are generally cost prohibitive.
Indeed there are some fungi and toxins associated with them that are considered potential carcinogens. For example, (you did not speciate your molds) Aspergillus flavus produces an aflatoxin that is a known carcinogen.
Quoting G. A. Payne et als: "Aspergillus flavus is an opportunistic pathogen of both plants and animals, and it produces one of the most potent naturally occurring carcinogens known." 
It is entirely reasonable to think that high levels of Penicillium or Aspergillus fungal spores found indoors in the air at high levels (or on surfaces that can send high levels of spores into building air), would pose a serious health risk to someone who is already immune compromised, undergoing chemotherapy, for example.
Basidiomycetes is the name of a very large group of fungi, including edible mushrooms. Basidiomycetes in buildings are associated with wood rot; they can produce spores that are very common in outdoor air, sometimes at high levels outdoors or inside and from outdoor as well as indoor original sources. 
A cautious approach would be to presume that a high level of basidiomycetes found indoors could be allergenic, and it is likely to indicate wet conditions, possibly extended wet conditions that would have invited a plethora of mold genera/species to grow in the building.
Depending on the mold test that you had performed, I would certainly not conclude that the mold families/genera you report are the only, nor even the most significant molds that may actually be present in the building.
Great site. I have a little guest house that was tested and the results showed a high level of Aspergillus penicillium in a hallway between bathroom and bedroom near a back door. The air sample in the hallway showed 161,351 per m3 and a raw count of 2.269. This was an air sample. There were other samples taken that were surface samples one in a dining area cabinet and one behind the bathroom toilet and both of those showed no spores. There was also an outdoor sample and...no spores. The back door which is where the small hallway is with the high samples is left open most of every day.
Is it possible that spores come in from outside and cause the high air sample reading there. There are no water sources in that area and no visible mold anywhere. Why would the air show results but the surfaces not show any results? I am unsure as to what to do next. The test was over $500 and I don't know how to proceed now.
I surely don't want mold around but am not sure if it is something inside the guest house due to the nonexistent source of water in that area. Any advise would help. - Jim
Jim that's a great Penicillium/Aspergillus question.
Penicillium and Aspergillus spores are very tiny - they can be down to even around one micron. So they are very highly mobile in air, and pass through a building just about as easily as a gas. Therefore you could have a large Pen/Asp mold reservoir somewhere other than where the air test was conducted - say in a wet crawl space over which someone installed fiberglass insulation into the floor above. A large but more "hidden" mold reservoir can put a high level of Pen/Asp into building air but there could be little or no mold on building surfaces where the air test was conducted.
When I find those conditions I usually also find that there are spore chains, not just individual spores, in the air sample, and I find the same spores in settled dust samples from the same building area.
The mold spore level in your report is quite high - much higher than would be explained by a normal outdoor air mold source.
In that case a thorough expert inspection is needed to find the mold reservoir source and to write an appropriate mold remediation plan.
Ok maybe you can help me understand my mold test report results. I had air samples indoor and outdoor of my home. We had several plumbing issues that gave us three floods in three bedrooms. The landlord did not follow proper procedures and resulted in crazy results. My outdoor was 764 cu and my indoor was 88,000 cu of black toxic mold. Why is is such a dramatic difference and is this unheard of? - Patrice
Patrice your indoor mold levels are
- not unusual for a flooded building with a large problem mold reservoir; I've seen higher still. Furthermore, the "count" is probably misleading in that there are almost certainly other genera/species besides "black toxic mold" and some of those may be more harmful and more ubiquitous in the indoor air
- something that needs to be tracked down to the physical source by a competent onsite inspection, history taking, and perhaps some modest invasive inspection of cavities that were flooded.
The reasons for the dramatic difference include that we are comparing completely different environments - an indoor air test (or was it a surface test?) in a relatively enclosed space with a large reservoir of a few species of wet-building-molds growing therein will give a much higher reading of those mold spore levels.
Outdoors, all molds are present everywhere, all the time. But they are generally more dilute in outdoor air - after all it's a bigger space than inside your home. We do, however, sometimes see elevated levels of particular molds outdoors, for example certain basidiomycetes shortly after the start of rainfall, and other mold spores seasonally and depending on weather conditions. Near the woods at some times of the year Ganoderma spores may dominate an air sample, for example.
So while it's usually comparing apples and oranges to compare indoor to outdoor mold levels, we might check outdoor air just to double check that something found indoors is really coming from indoors, not outside.
Ok thank you so much I will read more. I've been up all night trying to figure out if we are ok but it is def the owners responsibility to take care of this. Just want them to do it correctly. Thank you for the advice and clearing up some things for me. I believe all landlords/owners should have knowledge of your website it might help them in long run. This is a serious issue and a lot are not educated. I had to go through this to learn myself. But thanks alot. You are very kind.
My results were Basidiospores 530 cu and Penicillium/Aspergillus types at 1,100. My last one was Stachybotrys at 86,000 spores which gave me overall 88,000 total. So it was the black that was mostly found. Have five children in home and smallest always sick on why hired specialist myself. Our home is only 1300 sq ft. Been in hotel room for a week now so guess they are having issues with fixing I assume. So is that extremely high as specialist making it to be. Also can I save our clothes by washing since contaminated? - Patrice
Patrice, I appreciate your numbers, but I emphasize that depending on how a test is conducted and variations in building conditions, airborne mold counts vary by several orders of magnitude, from minute to minute. So it is absolutely not reliable to treat them as very accurate and it is much more important to look at the results qualitatively - your numbers show the presence of high Stachybotrys -that is a mold that's hard to disturb (big sticky spores) but may be found airborne if someone has been doing demolition. The Pen/Asp spores are smaller, easily airborne, pervasive, and can be an equally or worse health hazard.
Stachybotrys is a water-loving mold. It likes wet drywall, for example. And more, because Stachybotrys mold spores are black, big, warty fellows, they are both easy to see on building surfaces and easy to see in a surface, dust, vacuum, or air sample for mold. A result is that "black molds" are often over-reported and light-colored, hard to see and small mold spores are often under-reported.
Watch out: Since the same conditions that caused a Stachybotrys mold colonization in a building are highly likely to produce other mold genera/species too (we almost never find just one kind of mold in a building), and since some of those other (harder to see and under-reported) molds can be equally or even more harmful, a proper building survey is in order when high levels of Stachybotrys are found, and it would be a mistake to pay attention only to that infamous "toxic black mold" - there are plenty of other "toxic or harmful" molds that aren't black.
I emphasize that you cannot fix a mold problem by an air test because air tests alone don't reliably tell you where the physical problem exists nor do they diagnose the cause of mold growth - both of these must be accurately understood. You need a competent onsite visual inspection to find the location and extent of mold to be removed as well as to identify its cause.
If you see ACCURACY OF VARIOUS MOLD TEST METHODS you can read several articles that detail the reasons for wide variation in airborne tests (as well as "culture" tests)
Question: Just had a mold test done. We've been having health issues since November 2010. Our Pen/Asp group reading was 41,300 spores per cubic meter. Should we be concerned? Where can we get help? - Steven
Question: Just had a mold test done. We've been having health issues since November 2010. Our Pen/Asp group reading was 41,300 spores per cubic meter. Should we be concerned? Where can we get help? - firstname.lastname@example.org 7/1/2011
A high indoor Pen/Asp level suggests that there is an indoor mold reservoir to be found and cleaned up; in particular if the examination of the sample found spore chains, not just individual spores, that would be a compelling argument for indoor mold contamination that needs action. Because both Penicillium and Aspergillus spores are small they travel easily throughout building air and can indeed be a health concern. But frankly I must say it's troubling to read that you paid for mold testing but could not get a clear answer from the folks you paid.
Most likely what's appropriate is a competent visual inspection of the building to find the most likely mold reservoir locations and further inspection and maybe testing to confirm what's in those spots. That way you'll know what needs to be cleaned, the extent of cleanup, and the leak or moisture source that needs to be corrected as well.
See MOLD / ENVIRONMENTAL EXPERT, HIRE ? for help in understanding when it's appropriate and cost-justified to hire an expert to find an indoor mold problem source and write a mold remediation plan.
RE:"Our Pen/Asp group reading was 41,300 spores per cubic meter. Should we be concerned? Where can we get help?"
A high indoor Pen/Asp level suggests that there is an indoor mold reservoir to be found and cleaned up; in particular if the examination of the sample found spore chains, not just individual spores, that would be a compelling argument for indoor mold contamination that needs action. Because both Penicillium and Aspergillus spores are small they travel easily throughout building air and can indeed be a health concern. But frankly I must say it's troubling to read that you paid for mold testing but could not get a clear answer from the folks you paid. Most likely what's appropriate is a competent visual inspection of the building to find the most likely mold reservoir locations and further inspection and maybe testing to confirm what's in those spots. That way you'll know what needs to be cleaned, the extent of cleanup, and the leak or moisture source that needs to be corrected as well.
mold testing showed Penicillium Aspergillus outdoor 240 indoor 12,000 should we be concerned
also after clean up is re growth a problem? - Karen Kruger
Indoor air particle counts are highly inaccurate even if the number is precise, because of significant variation of the level of indoor particles from minute to minute and because of the great many factors that can make orders of magnitude difference in test results.
Details are at ACCURACY OF VARIOUS MOLD TEST METHODS
That said, an indoor count of 12,000 Pen/Asp spores per cubic meter of air is on the high side and suggests that there is an indoor mold source or reservoir. If the lab technician reported the presence of spore chains, not just individual spores, that is confirmation of a nearby mold source.
Air tests for mold without an expert visual inspection of the building to identify visible mold reservoirs or conditions that make a hidden reservoir likely are not worth much as they are often expensive without being diagnostic. It's likely that a proper investigation is justified, needed to find the problem and define the extent of cleanup. See MOLD EXPERT, WHEN TO HIRE for help in deciding if and when it's appropriate to hire an expert.
If a mold cleanup job is properly performed, the cause of mold growth is corrected too. Following that course of action, if you later find mold problems in the building, they're a new problem, not a re growth problem.
Finally, didn't you pay someone to conduct the mold tests you describe? Why can't the person you paid answer questions for you? I would think twice about hiring someone who simply collects samples and sends them to a lab, with no expertise, no interview, no case history taking, and no expert inspection of the building. And with no support to their clients and no questions asked or answered.
two rooms tested & that did not include the basement where it is covered in mold all over the place of all kinds, not to mention discovering asbestos too! Child's room test: Asp/Pen 7707, Cladosporium 54, Basidiospores 2134, Periconia/smut/myxo 54, Curvularia/Pithomyces 54, Stachybotrys 27, other unidentified Hyphae 54 total count 10030. Kitchen test: Asp/Pen 8801, Cladosporium 81, Periconia/smut/Myxo 934, Curvularia/Pithomyces 161, Other unidentified 134, Hyphae 321 Total 10459. Kitchen was tested because basement is really bad & kitchen at top of stairs reeks of odor & visible mold in walls, cabinets, carpet, dishwasher, & bathroom with black mold within shelving just off kitchen behind fridge area.
Air quality was not done in basement but should have been since it is sever down there on everything! Landlord told me to run the fans in basement & ceiling fan in kitchen w/windows closed, dehumidifier running & turn up the heat to dry it all out. Told by Environmental specialist bad idea.
To late. Daughter has sever allergies & has excessive long lasting bloody noses, headaches, rashes, amebic dysentery, stomach pains, ear aches, sinus infection.
I have had headaches,dysentery, ear aches, sinus infection, vomiting, both of us have had fevers. Other rooms have mold evidence & photographed such as dining rm, living rm - on flr, furnishings, belongings etc. 14 rooms I could not air quality test every one on limited budget.
Previous tenants moved out because of the same reason. Daughter & I exposed to this for a year at I am sure different levels. How worried should I be besides worried about daughters asthma. Landlord just wipes things with mold cleaner when here as if it fixes issue & it just grows back & stinks! Help??? Advice?? - Lee 9/23/11
Lee, our advice for tenants is at RENTERS & TENANTS GUIDE TO MOLD & INDOOR HAZARDS - there we give specific suggestions on how to proceed in a case like yours - I agree that from your description it sounds as if there is a serious mold problem in the building.
I am trying to locate a lawyer...environmental specialists ....and what a 6000 spore count means - Anonymous 7/18/2012
Unfortunately a spore count of 6000 means absolutely nothing without a
It's like saying "no soap, radio"
it said colorless, can it be taken to the 'genus' stage
Can "colorless mold spores" alone as a description of airborne mold be translated to a specific genus on the basis of that information alone.
There are about 1.5 million mold genera/species, about 75,000 that have been named and studied, and thousands of those are "colorless" or hyaline, spread across an enormous range of family, genera, and species. For example, colorless mold spores might be a surge of basidiomycetes common at verh high levels in outdoor air after start of a rainfall, unidentified spores - the lab had no idea what they were, or Penicillium sp. or Aspergillus sp. mold spores at high levels and including spore chains - that would indicate a nearby fungal contamination indoors.
We discuss this range of toxicity among mold spores at
or for a more broad understanding see
MOLD LEVEL IN AIR, VALIDITY discusses the general validity of counts of airborne particles.
Also AIR TEST FOR MOLD: ACCURACY explains why variations in test conditions can cause 1 to 3 orders of magnitude variation in the airborne particle count that is detected in a given test indoors.
In light of that point, let's not confuse precision (the number of digits in a number of airborne particles) with accuracy. We don't know what was in the 6000, and we don't have a clue about whether an accuratenumber would have been 60, 600, 6000, 60,000, or more. In fact it's a credit to the lab who produced the report you saw that the number was rounded to 6000 and not given as 6129 or something.
We don't know whether the count includes one spore type or hundreds of them, the spore size, toxicity, species/genus, nor what, if anything it indicates about the presence or absence of a mold contamination problem in the (unknown in all respects) building. You might want to take a look at
See MOLD STANDARDS for notes on numbers and exposure levels for "generic" mold spores - an approach that fails to recognize the wide variation in allergenicity or toxicity of individual species..
A mold "test" or "count" without an expert inspection and occupant interview, especially at comparatively low numbers in the few thousands of something that is unidentified - we don't know from your number if we're talking about one spore type or 20, is not very helpful.
About your request to find an environmental expert, based on just the spore count you gave, you should review MOLD / ENVIRONMENTAL EXPERT, HIRE ? for help in deciding when to hire someone. At page top the link titled EXPERTS DIRECTORY includes links to listings of mold consultants, attorneys, etc.
InspectApedia has no business nor financial relationship with any expert, consultant, or product discussed at the website.
Question: We are looking at buying a house that was previously used as a marijuana grow up. It has been cleaned up and City declared occupancy okay. Mould counts downstairs (where the grow up was located) are 31 raw count, spore count % total 38As/23Ba/8Co/15PA/15SPM total spores per m3 416. The upstairs (living area) are 34 raw count, spore count % total 21As/50Ba/29Cl, total spores per m3 448. These are the numbers after cleanup by the environmental company. The room has been fixed up and all problems solved. Are we safe with these numbers to continue to purchase this house? - Paula 7/14/2011
Question: Great site. I have a little guest house that was tested and the results showed a high level of aspergilus penicillium in a hallway between bathroom and bedroom near a back door. The air sample in the hallway showed 161,351 per m3 and a raw count of 2.269. This was an air sample.
There were other samples taken that were surface samples one in a dining area cabinet and one behind the bathroom toilet and both of those showed no spores. There was also an outdoor sample and...no spores. The back door which is where the small hallway is with the high samples is left open most of every day. Is it possible that spores come in from outside and cause the high air sample reading there. There are no water sources in that area and no visible mold anywhere.
Why would the air show results but the surfaces not show any results? I am unsure as to what to do next. The test was over $500 and I don't know how to proceed now. I surely don't want mold around but am not sure if it is something inside the guest house due to the nonexistent source of water in that area. Any advise would help. - Jim 7/18/11
Question: How can living room be higher than basement ? I bought a home where former owner grew pot. We did most of the renovations ourselves. Had air test done, and those were the results. I was very disappointed to see these high numbers. How bad is this ? - Lizabelle 11/4/11
Paula: I can't make any sense out of those mold counts and have no idea how the tests were performed - so it would be quite iffy to have an opinion about the mold risk in the home you describe. I'd start by insisting on some clarification from the folks you paid to inspect and test the home. If that "expert" can't help you then you didn't get much useful for their fee and you will need to find someone competent who will actually address the questions involved rather than just "perform a test"
Jim: that's a great Penicillium/Aspergillus question.
Those mold spores are very tiny - they can be down to even around one micron. So they are very highly mobile in air, and pass through a building just about as easily as a gas. Therefore you could have a large Pen/Asp mold reservoir somewhere other than where the air test was conducted - say in a wet crawl space over which someone installed fiberglass insulation into the floor above. A large but more "hidden" mold reservoir can put a high level of Pen/Asp into building air but there could be little or no mold on building surfaces where the air test was conducted.
When I find those conditions I usually also find that there are spore chains, not just individual spores, in the air sample, and I find the same spores in settled dust samples from the same building area.
In that case a thorough expert inspection is needed to find the mold reservoir source and to write an appropriate mold remediation plan.
About finding higher mold spore counts upstairs than in a basement, there are plenty of plausible explanations of which I cite two strong ones:
1. the mold spore reservoir is often but not always in the building basement. Leaks into building walls or ceiling or a flooded wet carpet, are examples of possible local upstairs mold reservoirs. If such mold reservoirs are found they will need to be removed.
2. if there was previously a highly contaminated building basement and that area was cleaned, it is possible that the cleaning contractor did not provider adequate negative air and dust control, blowing moldy dust upstairs where even though mold may not be growing on surfaces, there could then be a high level of moldy dust that shows up in screening tests for mold. This is a very very common event in my experience. If this is the problem, additional HEPA vacuuming, cleaning, wiping, are in order, followed by a follow-up test.
45 counts=2400 basement & 49 counts-2610 livingroom. Should I be concerned about these numbers ? I bought in 2008. Cleaned up in 2009. If these spores are now in my walls, ceiling. How much work is involved to get the entire house cleaned up ? I am very-very concerned. Thank you - Lizabelle
You are asking an important question that could involve significant cost and disruption to your home, while providing no information other than mold test results. ON that basis alone it would be improper and unethical for anyone to advise you of just what to do, of how much work is needed, or even of the risk level.
At MOLD EXPERT, WHEN TO HIRE we provide some help in deciding when it is probably appropriate and justified to go further in investigating a building for the possible presence of a mold problem.
Please take a look at that information and then use the comments box on that page if you have further questions and I'll do my best to be more helpful.
Beyond that step, since you paid someone to perform the "mold tests" on your home, if that person is not helping you to interpret the meaning of the test results then you are not getting what you paid for, and in fact are not getting much of value at all. (in my OPINION)
I just received the report (11/04) I did speak to them, and they are to come by (again) to see if he can locate the source. I thought maybe, this sight would shed a little more light on my situation. Your remarks have been helpful. I am "no"t prepared to demolition walls & floors. And was hpoing for a form of TREATMENT that existed to help situations, such as mine. - Lizabelle
take a look at MOLD SPRAYS, SEALANTS, PAINTS (article link at left) - I too wouldn't rush to do anything dramatic or costly, but I would not simply "treat" mold by some air or superficial means; the proper steps are
1. decide if there is a problem meriting furhter, even invasive inspection of building cavities
2. if step 1 finds a problem mold reservoir them mold is remove, physically cleaned, not just "treated" lest the process be ineffective, incomplete, and leave harmful particles (even dead mold spores can be harmful)
3. find and fix the cause of mold growth so that you don't have to repeat the process
They are suggesting a "Decamination process" No price mentioned yet. With this process, I need to empty my home of all plants and animals for 24hrs. I have many plants, a dog & a bird. Relocating for 24hrs would be hard. They have not "pushed" this process on me, but I am considering it. I live in a bungalow, and there is alot of "area" to cover. Also, there is a sumpump in the basement, would this be a cause ? Thanks - Lizabelle
A "mold decontamination process" that does not find and remove the problem mold as well as fix its cause, risks leaving harmful material in the building, wasting your money, and depending on the process used, possibly creating a new indoor hazard (such as overuse of ozone). The cost of a proper mold cleanup (if one is actually justified at all) is indeed significant, so the temptation to look for and buy a magic bullet is understandingly tempting. Magic doesn't work well off of the stage however.
I recently did a spore trap air quality test my 400 sq foot office, the test consist of a machine that cycled air for 5 minutes and contents were shipped to lab. The results were Inside: Pen/asp raw count 80 with 4,270 spores/cu.m and cladosporium raw count 40 with 2,130 spore/cu.m in addition other smaller count molds.
The outside levels are much lower pen/asp raw count 18 with 960 spores/cu.m and cladosporium raw count 8 with 427 spore/cu.m in addition other molds such as basidiospores.
I had been very concerned over the past five years i had occupied this office because I had become increasingly ill with so many symptoms. I had a urine test done that detects mycotoxins in the body and it came back that i was being exposed to moderate levels of Trichothecene which had caused a severe chronic systemic infection.
After reading the previous questions on your site, I feel like the levels in my building are low..So my question to you is will some infestations carry more mycotoxins or do all bad/toxic molds produce these toxins. I am just puzzled since there are no guidelines to how much mold is safe. Thank You - Nikki
Question: I have just received the air samples back. i have a total mold spore count under a kitchen sink of 2400. Is this cause for concern? - Chuck Helmke 7/6/2011
You must consider that there are many reasons why there is enormous variability in the level of indoor particles in a building from moment to moment, including particles such as mold spores. I describe these in an article found at MOLD TEST METHODS, ACCURACY
I have found several orders of magnitude in the airborne particle level just from moving the spore trap up or down at different heights in a room, waving a notebook in the air, rapping on metal ductwork, turning a fan on or off.
So a mold test that seems to indicate a problem (such as the one you cite) is a RELATIVE indicator - that is, it would be absolutely nonsense to claim that the Pen/Asp spore count of 80 spores collected over five minutes was an accurate measure of the actual mold exposure in the building.
When there is an indication of an indoor mold problem the most useful procedure is to inspect the building to find the problem source. Just testing alone is not sufficiently diagnostic.
Nikki the toxicity or Pathogenicity or allergenicity of mold species varies widely from harmless to quite serious, and because individual human sensitivity to molds also varies widely, there is a big range of possible effect from exposure to mold depending
Finally, you are right to be curious about the difficulty in writing mold exposure guidelines. We cite North American and world wide mold exposure standards at MOLD EXPOSURE STANDARDS but frankly any mold exposure "standard" can only be a very general guideline because of the following difficulties:
Do you know anything about the FDA approved levels for mold? - Sabrina 2/28/2012
Sabrina, the US FDA approves drugs and medications not mold. If you are looking for mold exposure standards, a very difficult topic, we provide a lot of detail at MOLD EXPOSURE STANDARDS and at MOLD EXPOSURE RISK LEVELS.
I discovered an HVAC leak and on subsequent inspection discovered significant mold in one bedroom and baseboard water damage in the master bedroom. The air quality test came back with Chaetomium in the spare bedroom at 200 with 15 actual spores found and Pen/Asp in the master at 3000 with an out door count of 800. I see by prior postings that having ceiling fans on could have increased the values. Both rooms had fans on at time of testing.
QUESTION 1: A protocol is being written and I am getting mold remediation estimates but when the clearance is done should the fans be on or off? I want an accurate test but at the same time I am nervous about the clearance.
I have lived in the house for a few years and the master bedroom is mine. I am constantly sick with upper respiratory issues (caught H1N1 in '09 and Pertussis in '10), have asthma, receive allergy shots weekly, and have been plagued with unexplained rashes and skin irritation since the spring of this year. Mold happens to be one of my more severe allergies and I have read that Pen/Asp can actually grow in human tissue.
QUESTION 2: Should I contact my ENT or other doctor such as a Pulmonologist? - Chris
if the fans are ON during clearance inspection and testing that will be the most aggressive and thus cautious procedure. Keep in mind that when someone objects, you can reply that after all you do intend to sometimes turn on the fans, so it's reasonable to see what you'll be exposed to when you do.
If I were on site I'd probably collect samples under exactly the same conditions as the original test, for comparison purposes but I'd also try a second test with the fan on. If I get a high problem mold level with the fan on, some additional cleaning in that area would be appropriate.
Ask your primary care doctor for advice on consulting a specialist. (Sept 28, 2011) Chris said:
We are looking at buying a house that was previously used as a marijuana grow up. It has been cleaned up and City declared occupancy okay.
Mould counts downstairs (where the grow up was located) are
31 raw count, spore count
total spores per m3 416.
The upstairs (living area) are 34 raw count, spore count % total 21As/50Ba/29Cl, total spores per m3 448. These are the numbers after cleanup by the environmental company. The room has been fixed up and all problems solved. Are we safe with these numbers to continue to purchase this house?
THANKS SO MUCH!!! - Paula
Paula: I can't make any sense out of those mold counts and have no idea how the tests were performed - so it would be quite iffy to have an opinion about the mold risk in the home you describe. I'd start by insisting on some clarification from the folks you paid to inspect and test the home. If that "expert" can't help you then you didn't get much useful for their fee and you will need to find someone competent who will actually address the questions involved rather than just "perform a test
I have to say that starting from a "raw count" of 31 mold spores /m3 of air, and one individual sample, and knowing nothing about how intelligently the sample was collected, even so, the raw count is so low as to be trivial and extrapolating results from a questionable test with trivial results is itself rather questionable.
Air tests for mold, used alone without an expert building inspection for visible mold and for conditions that are likely to have caused a hidden mold problem, are not reliable. See MOLD LEVEL IN AIR, VALIDITY for details.
I recently had my house tested. I have visual signs of mold in the attic that they did a tape test and was Stachybotrys *medium*. We did 2 Air samples in 2 of our bedrooms. Aspergillus/Penicillium was 852 and 2670. Basidiospores was 704 and 370, Cladosporium was 407 and 296, Myxomycetes++ was 222 and 74. Stachybotrys was 74 and 37. Now we both went into the attic could that be the reason for the small traces of Stachybotrys in the air samples? Yesterday I think I found the source of the Aspergillus/Penicillium.
I found a leak in one of the basement walls right where my Furnace is! I removed the panel and sure enough found black mold growing behind it! I did some tape samples that I will send out to find out if for sure it is the Asp/Pen. But where are the other ones coming from and should I be concerned? My wife has had bad cough with Phlegm for a couple months. I have had on and off stuffy noise for 2 years.
This is probably the cause! I'm removing the wall this weekend I sprayed it with MoldStat lastnight. Then I will fix the leaky wall. How long could these allergy symptoms last after I have cleaned up the mess? Do you think the attic is a huge concern? Last year I fixed the moisture problem due to a leaky attic hatch and moisture escaping into the attic. I also added a fan that also turns on due to high humidity. I'm going to put some plastic down and spray the attic down with Moldstat and scrub the boards, dry them then remove the plastic. With my levels is there any long term health problems that could happen to us? - Joe. 12/2/2011
please see the cases above and below this range.
The ceiling fan was on and the pen/asp lab test came back 2080 in our great room. No one is our house has ever been sick but the inspector is saying we have a problem.
Next - our basement had a count of 320 per cubic meter of air for Pen/Asp. Does this seem elevated ? - Coleman
The absolute spore count is not extremely high, especially considering that a ceiling fan was on at the time of testing, but since we don't usually find any elevation of Pen/Asp spores in a home your result is sufficient justification for a more careful and thorough visual inspection and some follow-up. Other factors such as visible evidence of a leak history into walls or ceilings, history of building leaks, flooding, and even an interview that finds that some occupants complain of indoor-air-quality issues when in the home and not when elsewhere all could suggest that further investigation is justified.
A general mold count of 320 spores per cubic meter is pretty low; but depending on exactly what is seen under the microscope, such a sample could still point to a nearby indoor problem mold source.
For example, Pen/Asp spore chains present in an air sample for mold almost certainly means that this is not outdoor mold but rather mold from an indoor source. That's because both Penicillium and Aspergillus genera produce their mold spores in long, fragile spore-chains. The spore chains break up into individual mold spores very rapidly as the particles move through air. So when I find spore chains in an air sample I know there is almost certainly a mold source nearby.
A visual inspection for leaks or leak / moisture problem conditions along with a case history of building complaints is how we can decide how much investigation is warranted.
To decide if you want to investigate further see MOLD / ENVIRONMENTAL EXPERT, HIRE ?
The ceiling fan was on and the pen/asp lab test came back 2080 in our great room. No one is our house has ever been sick but the inspector is saying we have a problem. - Coleman 7/9/11
Coleman, running a ceiling fan increases airborne particle levels by at least one order of magnitude over still air. It's a cautious and thus "aggressive" test approach.
The absolute spore count is not extremely high, especially considering that a ceiling fan was on at the time of testing, but since we don't usually find any elevation of Pen/Asp spores in a home your result is sufficient justification for a more careful and thorough visual inspection and some follow-up.
We'd need to know a lot more about the house, its age, materials, construction, leak history, occupants, and occupant complaints to have a view of what's needed.
Thank you for the quick response and we are getting it checked out. FYI - no visual mold present.
Next - our basement had an airborne count of 320 for Pen/Asp.
Does this seem elevated ? - Coleman
A general mold count of 320 spores per cubic meter is pretty low; but depending on exactly what is seen under the microscope, such a sample could still point to a nearby indoor problem mold source. For example, Pen/Asp spore chains means that this is not outdoor mold but rather mold from an indoor source. A visual inspection for leaks or leak / moisture problem conditions along with a case history of building complaints is how we can decide how much investigation is warranted.
To decide if you want to investigate further take a look at MOLD / ENVIRONMENTAL EXPERT, HIRE ?
Hi, This article is very helpful. My husband and I recently bought a 2 floor condo (2nd and third floor of a 2 family) with a basement. We have one half and the 1st floor occupants have the other side. Two years ago, during a large rain in Boston, water did enter the basement- more so on our side. As our neighbors were remodeling their basement (shortly after we bought unit and moved in) they noticed mold on their side of the sheetrock which triggered us to get some testing. As it turns out, their side with the mold exposed has very acceptable levels compared to the outside and the company we used. They have been using a dehumidifier religiously as well. Our side has not had a humidifier running for a couple months and more humid and did show higher levels of some molds, which I'd like to get an opinion on. There is no visual mold that we or the company who came in was aware of. Very minimal spots were on the sheetrock but were cleaned 2 months ago and have not come back:
The levels we see from our test that I'm nervous about are:
Pen/Asp group: 1810 counts/m3 (as compared to 53 for our neighbors and 267 outside)
Stachybotrys: 53 counts/me (as compared to 0 for neighbors and outside). I understand just one spore of this kind can be harmful.
Our total spore count was: 4470 counts/m3
Since we know the mold company is selling remediation services, its hard to know how severe our case is. This is a storage basement, not living space but still has contents we use on a regular basis.
Thank you for any insight someone could share. - Anonymous 8/9/11
"testing" that finds "acceptable" mold levels might be misleading if it was an air test - an air test is at real risk of a false negative. Your total counts are low but that is not a real assurance - see ACCURACY OF VARIOUS MOLD TEST METHODS for details
In deciding if it's appropriate to hire someone to look more carefully into the question of mold contamination, take a look at MOLD EXPERT, WHEN TO HIRE
4 year old has been to doctors 200 times. Two year old has been to the doctors over 120. walked out of the house two months ago with the clothes on our backs. Had a air test ,had the Pen/Asp but also had stachybotrys. 2ND FLOOR Center raw count 5 Count/m3 106 % of total 33.4
The guy who took the samples and gave me the report said the mold levels in my home are acceptable. Is stachybotrys at any level ok? The children are now under the care of a informed Doctor and getting better. thank you for your time. - Mom
Normally in a building that has been cleaned or has never had a water intrusion and indoor mold problem, we expect airborne mold spore counts from a properly-conducted test to be in the few hundreds of spores per cubic meter of air or less. And in a building not thought to have had an indoor mold contamination problem we don't expect to find spore chains of Aspergillus sp. or Penicillium sp.
Those raw counts you cite are very low, making me suspect that the inspection and test procedure have not homed in on the problem(s) in your home. Stachybotrys sp. is a big sticky spore that is not easily made airborne. I find Stachybotrys airborne most often when someone has disturbed a moldy surface such as moldy drywall during cleaning or demolition.
If you suspect that something in the home is causing or contributing to illness you should
How do I interpret a report for indoor sampling for Aspergillus that says: m3/760; raw score 18 ; 22.5%? Thank you - Deborah 3/20/2012
With respect, Deborah,
Surely you paid an "indoor air consultant" to come to your home, inspect, test, and collect what in your note appear to be air tests for mold (air tests alone, without a competent building inspection would be, to say the least, unreliable).
The person who conducted the tests knows the test conditions (still air, fans on or off, windows open or shut, other building and occupant factors) that are very important in deciding what added diagnostic information the test itself might offer.
Without that data, and from your single number alone, I think it would be unconscionable to pretend to risk your health and money on a simplistic answer of the meaning of the appearance of 18 individual mold spores in a sample. In sum, the test, alone, is meaningless.
4 year old has been to doctors 200 times. Two year old has been to the doctors over 120. walked out of the house two months ago with the clothes on our backs. Had a air test ,had the Pen/Asp but also had stachybotrys. 2ND FLOOR Center raw count 5 Count/m3 106 % of total 33.4 The guy who took the smaples and gave me the report said the mold levels in my home are acceptable. Is stachybotrys at any level ok? The childern are now under the care of a informed Doctor and getting better. thank you for your time. - Mom 7/7/11
Mom I do not understand your mold test - nor how any number of particles within a test can be more than 100% of the total number of particles found by the test. But I can say that betting a big expense on a raw count of five mold spores would be, in general, nonsense.
If your home has a problem with indoor air quality and indoor mold, or if there is reason to suspect such, those raw counts you cite are very low, making me suspect that the inspection and test procedure have not homed in on the problem(s) in your home. See MOLD / ENVIRONMENTAL EXPERT, HIRE ? for advice on how to decide if you need an actual expert.
REcently had a mold test done on a home I am looking to purchase. The Cladosporium spore leves was 550 and the raw count was 83. What does this mean? Is it dangerous? - Sue 5/25/2012
Sue, the mold count might be low - depending on what kind of test was performed and how it was conducted, and it might also be meaningless. You will want to ask the person you paid to inspect and test your home to help you interpret the meaning of the mold test lab report.
That person has key information that we do not - about the building interior, exterior, components, visible mold, leak history, and related data. In general, air counts alone, without a competent inspection, history taking, occupant interview, etc. are so unreliable as to be aptly criticized as junk science. See AIR TEST FOR MOLD: ACCURACY for an explanation.
Comment from Al:
Sue is the raw account was 83, and your total account was 550, this last number is based on the relationship ratio m3 and 1000 liters..remember 1 m3= 1000 liters,,,by looking the raw count # of 83, with a simple calculation you can find the total # based on 1 m3 or 1000 liters as a volumen.
Thanks Al, well put. Keep in mind that on the face of it, it would be absurd to launch a very costly building treatment based on 83 actual airborne particles collected in a single sample, regardless of the equivalent airborne concentration converted to spores per cubic meter of air.
Especially since Cladosporium, the king of molds, is the most common, prevalent, widespread fungus around. It sounds as if a competent building inspection was not performed.
A practitioner who just collects an air sample for mold, sends it to a lab, and tosses the report over the wall to you for your own decision on what action is needed, has not performed a useful job.
Watch out about mold test and spore count accuracy: To calculate the equivalent airborne concentration of any particle we need to know the actual raw or physical particle count, the percentage of the sample or trace that was counted or examined, and the volume of air used to conduct the test - usually by multiplying the test duratin by the liters per minute air flow rate of the particular sampler. Depending on how the test was conducted, however, we can see several orders of magnitude variation in the actual "number" of the result. Therefore let's not confuse test precision (the number of decimal places in the number or answer) with test accuracy (is the test off by a factor of 10, 100, or 1000 from the true building conditions.
I am a senior citizen and feel that I am not informed enough to know if i need to be concerned about the air sample i had done in my home. EMSL did an air sample in my family room and found
Aspergillus/penicillin in family room: Raw Count 22; Count/m2 464; % of total 38.7
OUTSIDE: raw count 1; Count/m2 21; % of total 0.2
A swab in my basement was taken because my ice maker in my kitchen leaked on a tile and a black spot looked like mole to me. Myxomycetes was "High"
Are those counts high? Do I need more extensive testing or professional remediation? - Viola Turner 8/22/11
Viola, EMSL is the giant among mold test labs, having bought up lots of smaller labs around the country, and in my experience their training and expertise are very good. (Disclosure, we have no connection with EMSL but I know some of the principals). I don't doubt the lab work itself.
But an air test alone to screen a building for mold, without a competent building inspection and taking of history of building-related complaints, is just very unreliable. A very low computed mold count (such as yours) is not usually a problem indicator but it might or might not have meaning, depending on what's actually going on at the building. I don't start with the assumption that an ice maker leak was or is the only leak concern at a building, nor did you say how much leaked, how much got wet, where water went - information that would help assess the risk of a hidden problem and help decide if invasive inspecting and testing were really justified.
And mold test swabs - do they mean anything? It depends. If the swab was examined microscopically it might give some interesting information, though in my experience swabbing crushes particles I'd like to use in the microscope to understand what's in the sample. And if the swab was used to prepare a mold culture ... keep in mind that only 10% of all molds that exist will grow in any culture whatsoever, so your "test" as a mold screen is 90% unreliable when you open the package.
Surely you paid someone to come to your home and do some kind of inspection and testing. It'd be fair to insist that that person help you understand the meaning of the test results. If the "test" person says "I just collect samples and send them to the lab" then their help was not worth much, nor their test in my OPINION.
Finally, while it's doubtful that tests alone were a reliable screen of your home for problem mold, you might not really need such testing. See MOLD EXPERT, WHEN TO HIRE ) to figure out if you need further testing.
I am really afraid of indoor mold spore levels and suffer from allergies and asthma. Why can't I get my indoor mold levels down to absolute zero?
Only in a "clean room" such as facilities used to produce electronic computer chips or in certain hospital clean room applications will we see the indoor particle levels even approach very low levels. And even then particle levels won't reach absolute zero even when extensive HEPA air filtering is in use. Common sources of indoor particles where there are people include skin cells, fabric fibers and low levels of inorganic debris such as soil particles.
As our mentor Dr. John Haines (NYS DOH mycologist, ret.) said repeatedly, "All mold is everywhere, all the time." By that John meant that mold spores and other dust particles (such as dust from the Sahara desert) travel widely, worldwide, in air. Therefore many mold genera/species are just about always available to colonize an indoor building surface or material. Only if you ran your home like a computer clean room, never opening a window or door to admit outdoor air, could you even approach a near-zero indoor mold or other particle count.
A "zero level" of indoor mold particles is not a reasonable nor necessary nor appropriate target to assure healthy indoor air.
To avoid an indoor mold problem we don't need to try to remove all particles from indoor air. Rather we need to find and fix building conditions that cause indoor mold growth, such as leaks or high indoor moisture. Details are at MOLD PREVENTION GUIDE.
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(Apr 4, 2014) ida said:
hello, i had an a mold inspection done in my apartment. Aspergillus/Penicillum has a raw count of 54 and a spore count of 350 in my bedroom. Also, in my bedroom was Cladosporium. Outside raw count is 3 and count /M3 was 20. Inside raw count is 8 and count/M3 is 53. Are these counts worth bringing up to the landlord, and are they any cause for concern.
Ida, as you can read in the article above, these are low counts, and the outside comparison is more or less nonsense anyway. But interpreting even low counts of airborne molds requires some intelligence, a building inspection, client interview, case history, building history, because even low counts can sometimes indicate a problem. A "mold count" alone is *NOT* a reliable indication of building conditions. THerefore if your mold tester did not answer your questions and you have to resort to asking us, who know nothing about your building, it's disappointing and suggests you paid too much for too little. Ask for your money back if your test person can't give intelligent answers to your concern.
(Dec 23, 2014) Kim said:
Hi. We hired a company to come inspect our home. Got lab report back today. Hyphal Fragments 2 26 4 52
Spore Trap Used
raw ct. spores/m3 % raw ct. spores/m3 % raw ct. spores/m3 %
Alternaria 1 13 3
Ascospores 3 39 16 9 117 14
Basidiospores 6 78 32 27 351 77 54 702 82
Bipolaris/Drechslera 1 13 5
Cladosporium 9 117 47 6 78 17 3 39 5
Curvularia 1 13 3
Colorless/Other Brown 2
Background debris (1-5)3 3 3 3
Sample Volume(liters) 75 75 75
TOTAL SPORES/M3 19 247 35 455 66 858
Can you please help? I've read about bipolaris and have questions.
In the article above we give some general guidance about the significance of airborne mold spore counts.
However, the meaning of any mold test is very dependent on building conditions at the time of the test, and no mold test makes any sense without a visual inspection of the building and occupant interviews.
If your mold test company cannot answer basic questions about the meaning of a test they provided, I would ask for a full refund of whatever fee you paid. After all, the test person was there to inspect the home not just to collect a sample, right?
Let me know if you get nowhere with the person who actually inspected your home and we'll take it from there.
17 June 2015 Amber said:
I just received the official mold report from an inspection being done in a house that I rent. I don't know how to read the reports, but I wanted to know if there was a way to find out if this specific mold that was elevated is making my family and our dog sick.
These were the molds that showed up with the top results on the report
Penicillium/Aspergillus: raw ct - 138; Spores - 1790; % - 77
Cladosporium: raw ct - 21; Spores - 273; % - 12
Basidiospores: raw ct - 18; Spores - 234; % - 10
Smuts/Periconia/Myoxmy: raw ct - 1; Spores - 13; % - <1
I would ask for a refund from anyone who inspected and tested my home for mold but who would not or could not give me any meaningful answer to the most basic questions about the home's mold contamination level.
The article above gives some general guidelines about when airborne mold counts are indicative of a water damaged building where significant mold contamination is or is likely to be present, but mere counts with no data about the building and still less data about how and where the tests were performed don't tell me a darn thing.
The counts you give have no meaning to me without knowing something about the building, its leak history, construction, materials, occupant complaints, visible mold contamination, identification of risk areas for hidden mold and results of their exploration.
Questions & answers or comments about the meaning of various airborne mold spore count numbers, mold level reports and acceptable versus unacceptable mold levels found in buildings
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 "A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm