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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".

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.

Extensive, in-depth articles about mold and other indoor air quality concerns are organized at our Mold Information Center.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

ACCEPTABLE MOLD LEVEL What are Acceptable Mold Levels in Buildings

Problems with indoor versus outdoor spore counts

Comparing indoor mold spore levels with outdoor mold spore levels

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."

Examine the indoor mold genera and species

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.

What indoor mold levels indicate a problem

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.

Example mold levels:

• Aspergillus/Penicillium in a "clean" residential building study was at a mean of 230,
• Aspergillus/Penicillium in buildings known to have a moisture or flooding problem it was at 2235
• Aspergillus/Penicillium in mold contaminated buildings the figure was 36,037.
• Also see MOLD STANDARDS to see what "acceptable mold level" standards have been recommended by different authorities, experts, and governments, world-wide.

Mold sample processing lab variation

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".

Surface samples of mold:

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.

Cultures of mold for Clearance Testing

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.

Mold Sampling Conditions Cause Wide Variation in Mold Test Results

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.

Questions & Answers regarding this article

Questions & Answers on mold level reports and mold inspections. 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.

Question: Pen/Asp spores were found indoors at 161,351 per m³. Why would air tests show mold and surfaces not show any results? What do I do next?

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

Reply: Small mold spores move through widely through a building like a gas and may be detected away from the actual physical mold colony or source

Jim that's a great Penicillium/Aspergillus question.

Penicillium and Aspergillisu 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.

Question: 88,000 toxic black mold spores per m³ - My outdoor was 764 mold spores per m³. Why is is such a dramatic difference

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

Reply: Indoor and outdoor mold tests in air are looking at completely different environments

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.

Question: Mold spore trap results in an office were Penicillium/Aspergillus 4270 spores / M3 and 2130 Cladosporium spores / M3 with low outdoor levels: are all molds equally toxic?

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 myotoxins 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

Reply: Modest mold spore counts indoors may still indicate a problem, and yes, mold spore toxicity variers widely among species and even within individual species; difficulty with mold exposure guidelines

About rather low but still-indicative airborne mold spore counts:

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.

About variations in mold toxicity or allergenicity

Nikki the toxicity or pathogencitiy or allergenicity of mold species varies widely from harmless to quite serious, and because individual human sensitvity to molds also varies widely, there is a big range of possible effect from exposure to mold depending

• not just on the mold species present (there will usually be more than one kind of mold present in a moldy building) but also
• the quantity of mold present
• the location of the mold present - and how much that mold reservoir communicates with building air and exposed surfaces
• variations in building moisture, light, darkness
• variations in building air movement
• even the substrate or material on which the mold is growing - mold toxicity may vary within an individual mold genera/species depending on what the mold has for food
• some molds produce higher levels of mycotoxins as well - see MYCOTOXIN EFFECTS of MOLD EXPOSURE

About mold exposure standards

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:

• Tests for the presence of mold in buildings and for the level of mold present in buildings present enormously varying results even for a given building and mold reservoir, depending on variations in building conditions and in how the test is conducted, and sometimes depending on variation in the skill of the mold test lab technician
• There is wide variation in the toxicity, pathogenicity, allergenicity of mold genera, species etc. as I explained above
• There is wide variation in individual susceptabilty to mold exposure. I've conducted in-situ tests of highly sensitive people in buildings and have found that some very sensitive individuals can experience serious respiratory distress at exposures to very low levels of certain very irritating mold spores - down to just 200 spores/M3 of air for some molds.

Details are at MOLD TOXICITY VARIATION and you'll also want to see MOLD EXPOSURE RISK LEVELS

Question: My air quality mold test found Indoor Pen/Asp count of 3000 spores M3 and outdoor count of 800, with Chaetomium present. Ceiling fans were on during testing. How should post mold remediation clearance testing be performed? Should I see a pulmonologist?

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

Reply: Repeat the same building air movement conditions during clearance testing as during original testing if at all possible, plus other suggestions for post mold remediation mold tests

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:

Question: Basidiospores 530 per m³, Penicillium/Aspergillus 1,100 spores per m³, Stachybotrys 86,000 spores m³ - been in a motel for a week.

My results were Basisidiospores 530 cu and Penicillium/Aspergillus types at 1,100. My last one was Stachybotys 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

Reply: What does a high indoor airborne mold spore level of Stachybotrys chartarum mold spores really mean

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: Our Pen/Asp group reading was 41,300 m³ spores per cubic meter. Should we be concerned?

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

Reply: A visual building inspection, indoors and out, is justified by high indoor mold spore levels

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 EXPERT, WHEN TO 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.

Question: Indoor Penicillium/Aspergillus mold spore count was 12,000 spores m³ of air. Should we be concerned?

mold testing showed peicillin aspergills outdoor 240 indoor 12,000 should we be concerned
also after clean up is regrowth a problem? - Karen Kruger

Reply: 12,000 Pen/Asp spores/m³ of air is high and justifies an actual investigation of your building

Karen,

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 regrowth 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.

Question: 3,416 m³ mold spores - We are buying a house previously used to grow marijuana. What do these mold counts mean?

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?
THANKS SO MUCH!!! - Paula

Reply: Mold test results that are vague or confusing deserve some interpretation and help by the person who inspected the building and performed the tests

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.

Question: Pen/Asp mold count was 2,080 m³ with the ceiling fan on. No one has ever been sick. The inspector is saying we have a problem.

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

Reply: Fans significantly increase the level of indoor airborne dust and particles but your count is not particularly high.

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 EXPERT, WHEN TO HIRE

Question: Low or meaningless "spore counts" - My home had low air test results for mold but found Stachybotrys. Is any level of Stachybotrys ok?

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

Reply: Low airborne mold spore counts and presence of mold in other tests might indicate an inadequate inspection and poor testing

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 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

1. Confirm that possibility with your doctor
2. If the doctor agrees that the indoor environment could be a factor, find a competent inspector who will actually examine the structure, not just collect tests.
3. Many other factors can of course cause illness and respiratory complaints besides mold. See MOLD EXPERT, WHEN TO 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.

Question: When should we want or expect to find an airborne mold spore count of Zero mold spores m³

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?

Reply: normal "clean" healthy outdoor or indoor air always contains particles including mold spores except in "clean rooms"

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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MOLD CLEANERS - WHAT TO USE
MOLD CLEANUP COMPANIES
MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD
MOLD CLEANUP by MEDIA BLASTING
MOLD CLEARANCE INSPECTIONS
  CLEARANCE PROCEDURES
  MOLD CLEARANCE TIMING
  ACCEPTABLE MOLD LEVEL
  MOLD CLEANUP, VISUAL CHARACTERISTICS
  MOLD CLEARANCE TEST, SUCCESSFUL
  MOLD LEVELS IN BUILDINGS
MOLD CLEARANCE: FOLLOWUP STEPS
  MOLD PREVENTION GUIDE
MOLD DOCTORS - ENVIRONMENTAL MEDICINE

MOLD EXPERT, WHEN TO HIRE
MOLD EXPOSURE, FOOD HAZARDS
MOLD EXPOSURE RISK LEVELS
MOLD EXPOSURE STANDARDS

MOLD FAQ's
MOLD INSPECTORS & MOLD TESTERS

More Reading on Mold Levels, Mold Test Interpretation, & Mold Prevention Methods

Mold Levels: allergenic or toxic mold: how much means a problem? It depends.
Validity of Cultures (settlement plates, culture plates, Anderson samplers, or mold test swabs) to find toxic mold in buildings
Mold in Fiberglass Insulation
Mold Prevention: Avoiding Mold Problems in Buildings by Using Mold-resistant Construction Products & Practices
MOLD PREVENTION GUIDE list articles describing steps to reduce the chances of future mold growth in buildings.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
• Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
• "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
• US EPA - Mold Remediation in Schools and Commercial Building US EPA
• US EPA - Una Breva Guia a Moho - Hongo - en Espanol

Mold Contamination Testing, Cleanup, Prevention: references & products

• The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
• Aerobiology, Building Science, Microscopy, & Laboratory References, an extensive technical bibliography
• Allergens: what they look like in buildings
• Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
• Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon)
• Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
• Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
• Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
• Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
• Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
• Clinical Mold References - Detailed bibliography of mold reference texts
• "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
• "Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
• "Disease Prevention in Home Vegetable Gardens," Patricia Donald, Department of Plant Microbiology and Pathology, Lewis Jett
  Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
• "Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• Fiberglass: Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
• Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
• Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
• Looking for Mold Procedure: what mold is often found where in buildings - simple technical presentation
• Meruliporia: the house eating fungus or "poria"
• Mold Action Guide: Step-by-Step Instructions, What to do about mold, mildew, and other indoor allergens
• MOLD APPEARANCE - WHAT MOLD LOOKS LIKE Photos of what mold looks like in buildings
• MOLD APPEARANCE - STUFF THAT IS NOT MOLD Photos of NOT-mold material that is sometimes mistaken for mold
• MOLD ATLAS & PARTICLES INDEX, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
• MOLD BY MICROSCOPE Mold under the microscope - photo identification of the most common indoor molds found in buildings
• Mold FAQs Answers to Most Questions about Indoor Mold, Mold Related Illness, Mold Cleanup, Mold Prevention
• US EPA: Mold Remediation in Schools and Commercial Building US EPA
• Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
• Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab or to any mold lab you wish
• Most Common Indoor Molds Found in Buildings, A Table of
• Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
• Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
• Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
• US EPA: Una Breva Guia a Moho - Hongo - en Espanol

OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold

Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.

• Fiberglass building insulation and HVAC duct work insulation hazards
• Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
• Other environmental risks: Asbestos, carbon monoxide, electromagnetic fields, environmental illness, fiberglass, MCS - multiple chemical sensitivity, toxic gases, etc
• Indoor Gas Sampling Plan for Residential Buildings lists a number of toxic indoor gases which we test for, depending on the building complaint and building conditions
• Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
• Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
• Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings, and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some help from a licensed pest control expert.
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