Interpreting Mold Spore Counts from EAA, Inc.

Mold Spores

Taking air samples for mold spores is easy. Knowing how to interpret the laboratory results is another matter.

There is no one level of mold that can distinguish a clean and moldy building. Outdoor spore types and concentrations have an important influence on the indoors. Unfortunately, the outdoor types and concentrations of mold vary quite widely over time and space.  In other words, some climates during certain times of year will have extremely high concentrations, and other climates at other times of year will have extremely low levels.  We can compare the indoors to outdoors, but realize that the outdoor concentration is a moving target!

Nevertheless, sampling may provide useful information and you should research some general guidelines for interpreting results.  In this post, I want to highlight two documents that are freely available on the website of Environmental Analysis Associates, Inc. (EAA), a commercial laboratory in San Diego, CA.

The first document is an article that was published in the Journal of Occupational and Environmental Hygiene in January 2005, titled A Regional Comparison of Mold Spore Concentrations Outdoors and Inside “Clean” and “Mold Contaminated” Southern California Buildings. You can download this article by clicking HERE.

The most intriguing recommendations in the article are found in Table V, Suggested Airborne Acceptance or Rejection Criteria.  Here are some of the suggestions:

75% of all clean buildings (as defined in the study) have measured total mold spore concentrations below these values:
Residential 1,200 sp/m3, Commercial 900 sp/m3
25% of all mold-contaminated buildings (as defined in the study) have measured total mold spore concentrations below these values:
Residential 1,300 sp/m3, Commercial  1,000 sp/m3
The second document that is available from EAA is called the AIR-O-CELL Method Interpretation Guide. Daniel Baxter of EAA is the creator of the popular spore trap, AIR-O-CELL, manufactured by Zefon International. In the guide, the following mold concentrations are recommended for interpretation:
  • “Clean Building” less than 2,000 sp/m3 total for all spore types and less than 700 of Penicillium/Aspergillus.
  • Possible indoor amplification: 1,000-5,000 sp/m3
  • Indoor Amplification likely present:  5,000-10,000 sp/m3
  • Chronic indoor amplification: 10,000-500,000 sp/m3
  • Inadequate flood cleanup or active indoor demolition of contaminated surfaces: 50,000-10,000,000 sp/m3 with predominant types beyond the common penicillium, aspergillus and cladosporium including Stachybotrys, Chaetomium, Basiomycetes, Tricoderma [sic], Ulocladium, etc.
These two documents should be used to give you some general guidance on interpreting your results. All sampling is just a tool that fits within the context of a thorough assessment. In the coming weeks I’ll be posting more on assessments, sampling and interpretation.
sp/m3 stands for spores per cubic meter
Image Source: Chin Yang available through EPA Image library

By Ian Cull

I'm I.A.N. the Indoor Air Nerd. I'm a speaker and consultant on indoor air quality issues. To learn more about me, click "about" at the top of this page.

74 replies on “Interpreting Mold Spore Counts from EAA, Inc.”

it was very interesting to read
I want to quote your post in my blog. It can?
And you et an account on Twitter?

This was a spore trap analysis conducted by OSHA. I was infected with Hypersensitivity Pneumonitis twice when I returneda to the classroom in the fall. What does 49,0000 total spores/m3 for a classroom result mean?
The other classrooms that were also tested their scores were 1,700 and 17,000 and the outdoor was 23,000 spores/m3.


Was the count 49,000 or 490,000 spores/m3? It’s not clear from your comment. If OSHA performed an assessment, they would be much better placed to interpret your data than I could with the limited information you provided.


on a recent air test of a basement that had previous water intrusion (4 months ago) and all drywall removed as a result, the indoor penicillium count was 1700 and outside was 120. I understand it is elevated compared to outdoors, but is 1700 considered a high number, in need of some form of remediation?


The person who performed the sampling should interpret the results for you. He or she can view the results through the lense of the assessment they performed. Air samples are designed to help you find an indoor source. If you don’t find a source, there is nothing to remediate. I have limited info, so it’s hard to say yea or nea. Generally indoor counts are lower than outdoor counts in normal buildings.

Any chance you can e-mail me a .pdf of this article “AIR-O-CELL Method Interpretation Guide”. I’ve tried downloading it from your link and the file seems to be corupt. Thanks a lot!


We just got back our air sample report and I am curious if you think this has caused damage to me or my family and should we leave while the walls are being torn out and replaced. The long term leak has been corrected and we have only been in our house a little over a year. Our 5 yr old has asthma and allergies and they have been terrible since moving into this house. I am also pregnant and worry if this can cause damage to the unborn baby. I can send you a copy of our mold report if you email me. Our outdoor count was 277 count/m3. Our sons bedroom was 453 count/m3 and our dining room was 17,547 count/m3. The mold is Aspergillus/penicillium. I am just looking for an opinion as we are lost on if this is dangerous to live with since we have been here a year. Thanks so much!

I’m not a doctor, nor can I provide a medical diagnosis. If you have nearby friends or family, it would be wise to stay with them while remediation is happening inside the house (especially if you’re unfamiliar with the remediation company). Make sure that the water problem is completely fixed so you don’t have to deal with this again. Also, make sure that you have a company totally independent of the remediation company come in to verify that the remediation was done properly. They will determine if the types and counts after remediation are reflective of normal background levels.

Is chaetomium spore count of 7 per m3 dangerous? Mold tester suggested “reverse air” and removal of wood underneath the sink. Is that a reasonable remediation? Is it likely worse than that? We are in escrow on this house.

Thanks for replying!! I didn’t see any actual mold, but I did see the wood under the kitchen sink that looks like it’s had water damage. The owners of the house have reported pipe back ups in the past in the kitchen, so I’m guessing they have had some pipe problems under there in the past. The pipe aren’t actively leaking now. I’ve also been in the crawl space under the house under the kitchen. The soils is dry and I don’t see any active leaks, though it does look like the wood there has been wet at some point. The wood isn’t soft or anything, just discolored (but nothing that looks like actual mold). If we get rid of the wood under the sink, will that do it? “Reverse Air” treatment? is a 7 per m3 indication of widespread contamination or a smaller confined location (like the wood under the sink)? Thanks again!!!

7 spores per cubic meter probably equates to a single spore on the sample collected (the numbers get extrapolated). It is unwise to base any major decisions over the presence of one spore in one sample. Although Chaetomium is a water damage indicator, there is not enough information to make a strong decision. If I were the consultant, I would have conducted more sampling and performed a deeper visual inspection using borescopes.

I am about to invest quite a bit of money for mold remediation (barriers, air scrubbers, decon chamber, etc.) in basement, crawlspace and foyer. Based on your knowledge, could you opine on how quickly I should get started based on an extract below of results from my report? note: I have many allergies and have specific allergy to Penicillium.

Outside Control — 1280 m3/36%
Basement — 3200 m3 / 81.6%
Crawlspace — 2160 / 96.4%
Foyer — 920 / 50%

— Chaetomium
Outside Control — 40 m3/1.1%
Basement — 40 m3 / 1.0%
Crawlspace — 40 / 1.8%
Foyer — 160 / 8.7%

Other common allergen organisms are elevated also, but these concern me the most. Not asking for medical advise, just your best guess judgement. Thanks,



Assuming there is visible mold that has been identified, I would go ahead and do the remediation sooner rather than later. Make sure that the underlying moisture problem (which caused the mold growth in the first place) gets addressed. I can’t think of any benefits of starting the remediation later.


I am a property manager and did remediation in an apartment that we just acquired due to a HVAC leak. We repaired the leak and replaced drywall in the apartment. The resident asked us to do a mold testing in her apartment due to the musky smell. Can you please let me know if these results might cause any health issues or concern?
Indoor: Raw Count: 68 Count/m3: 2800 Percentage of Total:86.2%
Outdoor: Raw Count: 659 Count/m3:27100 Percentage of Total: 38.2%

Total FungI:
Indoor: Raw Count: 70 Count/m3:3250 Percentage of Total:100
Outdoor: Raw Count: 1723 Count/m3:70900 Percentage of Total:100

The analytical results in the unit had lower levels of Aspergillus/penicillium mold spores compared to the outside but the percentage of the total amount was higher in the unit sample.

What does that mean? Is it harmful? What is the test was taken 1 week after remediation and we have not heard from the resident since then about any problems. This test was taken last year. Now claims that her son suffers from asthma caused by the mold in her apartment.

Carol, The most important thing is to physically remove the mold and solve the moisture problem (which you did). It sounds like the mold testing done was very limited. That type of limited sampling is only able to find glaring problems. That type of limited sampling doesn’t provide you enough data to confidently state that the airborne levels of mold have returned to normal background levels.
Trying to prove that health effects were caused by a specific mold problem isn’t totally straightforward. Current science shows associations between water damaged buildings and health effects such as wheeze, cough and upper respiratory irritation. Although the Aspergillius/Penicillium indoors is an order of magnitude lower than outdoors, it’s not just mold that causes health effects in water damaged buildings.
Email through this link if you would like to hire me to go in any more detail:

Hi Ian.

We had a bad carpet cleaning job done in our basement and it took 2 days to dry. We recently had them recleaned (3 months later) and we were told it looked like mildew. We had a mold test done and had a Chaetomium count of 3 or 39.9 spores /m^3.

The carpet surface test was 0 for the luminometer

We saw this in the air rest. However we just had the carpets cleaned the day before the test!


Hi Ian,

Our house has 3 levels including a finished legal basement suite, and it will be 3 years old this March. We had the carpets in our basement suite professionally cleaned this past Tuesday (it is now Thursday), and the cleaner said it looked like there was water damage on the carpets. We have a 4 month old son so this information was quite alarming to me. I asked the previous tenants who moved out in September if there was ever any water damage in their suite, and they told me they had the carpets cleaned in August but they stayed wet for 2 days. Obviously that carpet cleaner was inexperienced or had faulty equipment. Needless to say, I wanted to get a mold test done, so I had a reputable company come in yesterday (Wednesday). He tested the air inside and outside the basement suite, and also did a swab of the carpet. The swab of the carpet came back negative, but the air samples yielded the following results:

Basement Outside: 0 Raw Ct, 0%, 0 Spores/M3
Basement Inside: 3 Raw Ct, 6%, 39.9 Spores/M3

The report stated that the concentrations of chaetomium detected were not significant, and that the indoor sample is considered normal. However, I am still worried that chaetomium was detected at all! I do not want my infant son to become sick, so please let me know if there is anything I should be worried about. At this point I am ready to rip out all of the old carpet in order to solve the mold problem!

Thank you in advance for your reply!


Do you still see or smell any mold? That is a quick indicator of a problem that is more accurate than many will admit. If you don’t see any mold, you don’t smell any mold, and a surface sample didn’t reveal anything, I would then presume the 3 Chaetomium spores that were found were remaining from before (rather than new mold growth).

I personally like to take duplicate samples at all locations. The two samples you have are not sufficient enough to make strong recommendations. Keep the basement dry (below 60% relative humidity), filter the air (typically with existing HVAC system) and you should be fine. You may also want to consider purchasing or renting a HEPA vacuum and cleaning all the contents that may have been in the basement when the carpet was moldy.

For future reference, 9 out of 10 times I would recommend replacing moldy carpet rather than trying to clean it.


Hello again,

My husband Matthew just told me he also posted on this blog, so I apologize for the duplicate question!


Hi Ian,
My family and I are renting an apartment and we found visible mold on furniture and walls that grew over a few months at most. We had testing done and it came back 3933 total mold spore count for out room and 2289 total mold spore count on our son’s room. the outside count was 222. We have all had respiratory symptoms. We are sending the report to out landlord to see how they want to proceed with remediation, the testing company recommended professional remediation. the testing company also recommended that we not stay there until the remediation is complete.
Do you think these counts are dangerous, and should we vacate the apartment? We have a 2year old and are concerned for his health.
Thanks, Katie

There is enough evidence out there on the health effects of mold to substantiate your concern. All the visible mold should be remediated. That typically means that porous materials like upholstered sofas should just be removed and replaced (rather than trying to clean it). Make sure you address the moisture problem that caused the mold to grow in the first place. Why was the apartment unit humid enough for mold to grow? Is there an exhaust fan in the bathroom or kitchen that the landlord hasn’t fixed?

I can’t make a recommendation to stay or vacate. That would be a decision for a medical professional to make. Remove the mold as quickly as you can and air out the unit as much as you can (open windows when appropriate).

Let me know how it goes!

Hi ian. My wife and I just bought a new house and since we have a 1 year old decided to do a mold test. We found some mold on the air conditioning unit in the garage which i cleaned with bleach and mildew cleaner. The inside of the AC looks like new thanks to a MERV 16 filter i installed (in place of the existing OLD MERV 9) and a UV-A/Titanium Dioxide PcO system (Lennox PureAir).

We decided to get a test to be on the safe side and the test came back as comparing favorably with the outdoor sample except for a single spore of chaetomium in the living room. There is no evidence of water intrusion in the house and the tester said that although he doesn’t like to see even a single spore, the spore may have come in on a package, shoe. etc.

We simply expected to have a perfectly clean report and this threw a wrench in that expectation. What do you recommend? Is a single spor in only one of the tests cause for any concern? Both my wife and I can be obsessive about such things and we are looking for answers and reassurance.

Thanks for this site!


I always advocate taking two samples in each sampling location. That often results in 6 total samples. 2 in the complaint area, 2 outdoors as a reference, and 2 indoors in a non-complaint area (which also serves as a reference). When I take duplicate samples in one location, finding 1 spore in 1 sample doesn’t mean much (especially when it was not in the second, duplicate sample). Because you only have a single sample, you won’t have as much confidence in your results. Nevertheless, I rarely get concerned about a single spore, even if duplicate sampling wasn’t performed.


Also. Mold imspector said he was not too worried because the spore wasn’t accompanied by Aspergillus or other spores usually found along with chaetomium.

I had indoor air tests done for mold in my chidren’s two bedrooms, and the results came back at about 3,000 spores/cubic meter (mainly basidiospores and cladosporium). However, the company didn’t do any tests of outside air for comparison. Does that mean that the test I paid for is useless? Is there any useful information I can glean from such a test without a sample of the outdoor air? Thanks.

I would say “close to useless”, rather than “totally useless”. A single sample can only be useful if there is massive contamination. But typically at that point, there is little need to sample the air.

Basidiospores and Cladosporium are common outdoor fungi, with the later being able to grow indoors, especially on dusty surfaces. The total concentration is relatively high, but very few conclusions can be drawn from such limited sampling.


Hello, I am looking to purchase a home that I know was under water for a few months. The house has since been cleaned up and remodeled. The sellers just had a spore trap analysis done. The sample was taken from a ductwork Vent. Alternaria came back at 240/M3 and Aspergillus/Penicillium 760/M3 (40.3%). Can you tell me if we should be concerned about these numbers? What would you suggest is the best way of getting rid of a mold problem?

Taking an air sample inside the ductwork is unconventional. Was only one sample collected? It looks like this information is almost useless. If you see or smell mold, you should hire a consultant to assess the situation.

We just received results back and are very concerned. We do not have any water leaks from pipes roof etc (checked by two companies), but the mold inspectors told us that we likely have humidity coming up through the uninsulated crawl space underneath.
The mold levels are we are similar to outdoor except for penicilium/aspergillus
outdoor: 500 spores/m3
indoor: master bedroom 7220 spores/m3
indoor: daughters bedroom 12920 spores/m3
we are frankly freaked out. Should we move out of this home as it is a rental? We just washed down the entire room and all floors, clothes, toys etc, one day prior to the testing. Not sure if this kicked everything into the air. Just received the results tonight and the mold company is closed until Monday and so not sure what to do???
Would really, really, really appreciate any feedback.

It’s a bit counter intuitive, but many cleaning activities can stir up settled mold spores. When a room has high activity and air movement, it can have mold spore levels 1,000 times higher than when the room is empty and still. What made you think to have a mold inspection done in the first place? Did you see or smell any mold? Did the inspectors take any surface samples of any mold found?

The numbers you have are high, but I need more information to better assess what is going on.

Hi Ian,

Thanks so much for your feedback. Please let me give you a little more of the background to see if you can make a recommendation for us. This might be your longest post, but here goes:

We noticed the mold probably about two weeks before Christmas. At first, my wife just found a few spots of mold on some clothes in the closet. She took those items out and basically washed them twice or pitched them. Then we found some mold in the same closet on some shoes. That’s when we checked everything in all of our closets for mold. It turned out we had mold in three of our closets, on some of the clothes and some of the shoes. The mold seemed to be on items that were not worn in a long time, were in areas of the closet that where the air was stagnant or close to the floor. All were on outside walls on one end of the house.

At first we just either took the clothes out and washed them, pitched them or dry cleaned them. We didn’t wrap them in plastic first, which I understand was a mistake. And then we also probably made a big mistake by taking the shoes out of the closet and cleaning them on the floor in the bedroom. They were wiped with bleach, and then later vinegar, and then later placed in the sun for the afternoon.

Then, when we went into the bedrooms to wash everything down. That’s when we found mold on in three more spots: on some wood slats on the bottom of our bed, mold on the back of our bedside table and then mold on the back of one dresser. That’s when we got freaked out. At that point, we through away the bedside tables, the beds slats were washed with bleach and then vinegar and same with the dresser back. Then we washed all the surfaces in the room and closets. We washed all of the kids clothes and most of the clothes in the closet. Again, we didn’t contain the room and seal anything off prior to cleaning everything. This happened over the weekend and through a Monday. We felt like everything was clean at this point. Then on Friday before Christmas, we had a mold company come out and test. The technician gave me some comfort and saying that he saw no evidence of mold any longer. He checked the closets wall and the crawl space underneath. He said that the mold appears to be from high humidity levels, like from humidity coming up from the crawl, and also perhaps condensation on the uninsulated walls in the closets. We live in Los Angeles area, so uninsulated houses are not uncommon. We also had the rainy-est three week period in the last five years around this time. All mold was only found in these two rooms.

It took two weeks to get the results. That is what is posted previously above. The room with the highest reading was the room where we cleaned the shoes. The other room that had mold in the closet was where the bed and end tables were kept. These results freaked us out again and the mold company was closed when we called back. So then over the weekend through last night, we went room by room and used a HEPA (<0.3micron) vacuum and vacuumed every surface in the room. In the closest we lightly vacuumed the clothes. When we did this, we kept the bedroom doors closed and ran a large HEPA (<0.3micron) air purifier at the same time to help clean the air. We are running the air purifier room by room around the clock. We have since done this vacuuming/air cleaning to the entire house.

Sorry this is so long!!! So, here is our predicament. The mold company wants $3200 to clean this properly. We rent and our landlord told us no-way. We are moving out in May but can’t leave sooner. We will have a mold company come out and retest, but we are unsure about paying to have them reclean everything, as from their phone consultation, they are proposing to do what we already did. But obviously, do it properly, and not the undisciplined way we first did it. It is a ton of money but we have a 3 year old and 1 year old and don't want to cause risk to them (we have been sleeping in the other end of the house for the time being). We are trying everything we can do ourselves to help fix this problem if possible.

So a few questions:
1. How long should we wait until we retest? I’m interested in your comment about high activity causing elevated mold counts. It seems we haven’t gotten rid of the active mold, but obviously have mold spores in the air. We want to run the air purifiers for a few days to help finish cleaning the air. Should we wait a few days to retest?
2. For a retest, what levels would be acceptable? Use the rule – less spores inside than the outside mold levels?
3. Do you think we are OK to wait for a restest?
4. Anything else we can do ourselves to make this situation better?
5. If we have gotten rid of all the visible mold, is there risk of moving clothing, etc to the new house and bringing the mold with us? I hear there is always a small amount of mold spores that you can never get rid of but we don't want to transfer a problem to the new home.

Thanks so much for all your help/advice/comments!!!


The concern I have is that no one has properly determined why the mold was growing in the first place. You may do all this cleaning and testing, only to have the mold come right back because no one is addressing the root cause.

Mold needs moisture and food. The moisture is likely coming from condensation. Condensation happens when there is high humidity in the air and a cold surface. The closets on exterior walls are cold in the winter. The humidity may be something temporary from the recent rains, but it may be from something more permanent, like humidity from respiration or lack of an exhaust fan in a bathroom.

The food mold uses is the dust and skin cells that have accumulated on various surfaces throughout the house.

So before any talk of re-testing the air, I would make sure that the moisture problem gets addressed.

If the moisture source has been solved, all mold growth has been removed, and many of the remaining mold spores have been removed by HEPA vacuuming and air filtration (even if only done by yourself), your home should return to normal background levels.

We recently had remediation on our house and got our air quality report back. For penicillium/aspergillus we scored 210/m3, cladosporium was 80/m3, basidiospores were 27/m3. Then we had “marker” spore types, including stachybotrys and chaetomium. The numbers for those were 20/m3. Additionally, there was bipolaris/drechslera, smuts, periconia and myxomycetes which measured at 54/m3. My question is, is it alarming that stachybotrys was measured at all? We are expecting a child in April and I’m concerned that we’re not bringing her into a safe environment. Is stachybotrys normally found in homes? At this level, with chaetomium, is it a concern?



Although there are certainly Stachybotrys and Chaetomium spores that can be found in even a “normal” home, finding lots of both of these spores usually indicates a problem. Can you give me the raw count of these spores (not the number based on a full cubic meter of air)? Knowing the raw count puts things in context.

Some consultants have a zero tolerance policy for Stachybotrys during post-remediation verification. Others don’t get concerned until a raw count of 10 has been exceeded. So, is it alarming? It depends on who you are asking!

Your results certainly leave open the possibility that the remediation contractor did not do a good job of remediating the mold and/or not a good job of containing the mold during the work.



I am a renter in NJ. Shortly after having moved in (December 2012) we noticed mold accumulation along the window sills and bathroom surfaces of our unit. When we reported this to the management they indicated that this was “normal” for the complex and that tenants were responsible for “staying on top of it”. We began regularly wiping the contaminated surfaces and proceeded to place multiple “Damp-rid” products throughout the unit. Throughout the summer and fall we began noticing an increasingly strong “musty” smell and began discovering that every item with a porous surface (which was not used or moved on a weekly basis) had begun to accumulate large visible patches of mold growth. Items ranged from luggage, books, stereo speaker covers, clothing, shoes, purses, backs of picture frames… even items which had been cleaned and folded in dressers long before our move. We notified the complex immediately upon discovery and even brought some items into the office to illustrate the issue. Multiple maintenance visits within the unit led to head scratching and promises of having our items cleaned. For months we were told that something would be done to address the worsening issue and that it was being “escalated”. One visit led to the discovery that the complex’s pumps and fans had failed and that a large amount of standing water had accumulated in the crawlspace which lies below our unit. Industrial fans were put in place to dry out the space but the conditions continued to deteriorate within our home. At the beginning of November mold testing was finally performed. The results indicated the following:

Living Room–
97 Raw Count
363,117 spores/cubic meter

117 Raw Count
549,959 spores/cubic meter

58 Raw Count
754 spores/cubic meter

160 Raw Count
2,080 spores/cubic meter

The report indicates 10 types of mold in the living room and 6 in the bedroom– with “aspergillus/penicillium-like” noted as the overwhelming primary (64 Raw Count in the living room & 97 Raw Count in the bedroom). The outdoor area indicates 6 types– with “basidiospores” (25 Raw Count) and “cladosporium” (24 Raw Count) as the primary counts. The crawlspace results show 5 types– “cladosporium” levels (103 Raw count) are the highest followed by “basidiospores” (31 Raw Count) and “aspergillus/penicillium-like” (23 Raw Count).

The contractors who completed the testing stated that the “results do not support the concern that the flooded crawlspace contaminated the apartment” as the primary mold contamination was shown to be of separate varieties. There are no visible plumbing issues or leaks, so the “most obvious conclusion is that the humidity in the air is causing these mold issues”.

After much back and forth, the complex has just stated that they are unwilling to address the issue, as the estimate they obtained was “astronomical”. They also stated that they are not responsible for any damage or loss of personal property, so will not offer any assistance with remediation. They have offered us the option of terminating our lease without penalty as no other units are available. Due to the large number of displaced Hurricane Sandy victims in our area housing is exceedingly hard to obtain. Once we have found a place we are unable to relocate our contaminated items, for fear of bringing these issues to a new home. The condition of the apartment has deteriorated to the point where not only is our personal property continuing to be consumed, but my roommate and I are now suffering eye, nose, and throat irritation, difficulty breathing (I also suffer from asthma), and persistent coughing.

I’m wondering if you have any thoughts, suggestions, or references that may be of assistance. Thank you in advance for your time.

The conclusions drawn by the contractor are not necessarily correct. They are saying that the mold in the crawl space is not getting up to the unit. I agree with that. They are missing the point that it is highly likely that it is the MOISTURE from the crawlspace getting into the unit and causing the mold in the unit above. Do you see the difference? Mold spores may not have a pathway to get into the home above, but moisture can easily diffuse through most building materials.
Besides moisture from the crawl space, I would also check exhaust fans in bathrooms and in the kitchen. Are they exhausting air properly?
There is high humidity in the air. The only time that would be your fault is if you weren’t operating the exhaust fans during showering or cooking.

I recently was exposed to high levels of mold.
Januany 9,2013 1st Test:
Chaetomium Outside Level: 0 Inside Level: 3999 Cts/m3
Cladosporium Outside Level: 160 Inside Level: 240 Cts/m3
Hyphal Fragments Outside Level: 0 Inside Level: 30 raw 400 Cts/m3
Penicillium/Aspergillus* Outside Level: 160 Inside Level: 2,119,150
This first test was done after landlord tried a quick 2×2 repair in my ceiling from a leaking roof.
January 26, 2013 2nd Test:
Arthrinium Outside Level: 0 Inside Level: 96576 Cts/m3
Chaetomium Outside Level: 0 Inside Level: 98109 Cts/m3
Hyphal Fragemts Outside Level: 0 Inside Level 930 raw 12397 Cts/m3
Penicillium/Aspergillus* Outside Level: 80 Inside Level: 171690 Cts/m3
Scopulariopsis Outside Level: 0 Inside Level: 50587
Also positive for asbestos as well.
What are your thoughts on this level of spores.
Thank You.

We were recently flooded during hurricane Sandy. We tore everything out and sprayed with a mildewcide prior to rebuilding. Please look over and let me know if we should rip everything down remediate and start all over. In anycase we just had an air quality and swab test done.

The swab showed:
Organism Spore Estimate Mycelial Estimate
Chaetomium Light ND

Here are our results from air sample:

Raw Count Count/M3 %of Total
54 360 84.3%

Raw Count Count/M3 %of Total
4 27 6.3%

Raw Count Count/M3 %of Total
3 20 4.7%

Raw Count Count/M3 %of Total
2 13 3.0%

Raw Count Count/M3 %of Total
1 7 1.6%


First off, sorry to hear you got flooded. Before I can answer your questions intelligently, I need to know a few things. What surface was swabbed and why was it swabbed? Is there mold growth that wasn’t removed?

Was there only 1 indoor sample collected? If so, the information is nearly meaningless. I’m not sure what the “inspector” was trying to accomplish.

Do you smell any mold odors in the home? See any growth?


Hi Ian,

Could help me look at the air sampling analysis results below? Do we need to be worried about it? We didn’t see any mold or smell it.
Raw Count Spores/m3
Ascospores 49 490
Basidiospores 5 50
Cladosporium 9 90
Myxomycetes** 7 70
Penicillium/Aspergillus 8 80
Stachybotrys 9 90
Total Spores (Cts/m3) 81 810

Normal practice is to compare indoor samples in a complaint area to other outdoor and indoor references. It is quite difficult to make any interpretations based on a single sample. The air sample did have 9 Stachybotrys spores, which are a water damage indicator. Is there a history of water problems in the house?

Hello Ian,
Thank you very much for taking your time to help us and I am so glad that I found a professional engineer specialized in these types of problems. We purchased a two story town house here in south FL and a year after we noticed a musty smell in one of the bed rooms upstairs. We hired a professional company to do a mold inspection and these are the results:

1-Sample taken from bulk air in the smelly Bedroom

Spore Types Raw Count Count/m3 %
Aspergillus/Penicillium-Like 12 80 86
Cladosporium 2 13 14

2- Sample taken from wall cavity in the same bedroom

Spore Types Raw Count Count/m3 %
Aspergillus/Penicillium-Like 1 49 50
Ascospores 1 49 50

3-Sample taken from outdoor (right in front of entrance door)
Spore Types Raw Count Count/m3 %
Aspergillus/Penicillium-Like 80 533 94
Cladosporium 2 7 1
Curvularia sp. 2 13 2
Ascospores 1 13 2

We removed the carpet, made some holes in the walls and check the attic for leak, but no presence of mold was visualized. There are only two evidence at this point, the smell and this air sampling report. The smell is driving us crazy and I have been coughing more than usual since we move in. Please let me know about your thoughts on this.

Nothing in the air samples is a glaring red flag. I would be much more concerned about the moldy odors. Is the odor limited to one room? Smell any outlets, phone jacks or other openings in walls (especially exterior walls). Smell the air coming out of the air conditioning system.

Is the odor intermittent or constant? If intermittent, keep a log. Do you smell it more on wet days? More when the room is hot? More when the sun is beaming into the room?

Can everyone entering the room smell it, or only some people? How would they characterize the odor? Email me offline through if you want me to spend some time with you on the phone walking through all of this.


The surface that was swabbed were exposed studs, and the inspector thought that there was some mold on there. When we rebuilt we sprayed the surfaces down with a Mildecide but apparently that may not have been enough.

There were 2 indoor samples. We live in a bi-level home so he sampled the upstairs where there was no flooding. As well as the outside for a baseline sample. So the results I gave you before were for the downstairs where we had flooding. The upstairs and outside results are as follows:

Raw Count Count/M3 %of Total
5, 33, 33%

Raw Count Count/M3 %of Total
7, 47, 47%

Raw Count Count/M3 %of Total
3, 20, 20%

Raw Count Count/M3 %of Total
4, 27, 13.5%

Raw Count Count/M3 %of Total
9, 60, 30%

Raw Count Count/M3 %of Total
15, 100, 50%

Raw Count Count/M3 %of Total
2, 13 6.5%

There is a funky smell that I can’t put my finger on, don’t see any growth. But since we rebuilt so quickly we are concerned that maybe the proper dry time wasn’t given and there could be mold behind the dry wall.

You had a few Chaetomium spores in the downstairs. Those can be a water damage indicator. I’m more concerned about the mold odors you can smell.

$1,650 for the services you described is very expensive, unless performed by a nationally recognized expert. Then again, if the inspector was a nationally recognized expert, he/she would have answered your questions. I would say what you paid is not in line with the services you received. Again, so much depends on the credentials of the person performing the assessment.

Hey I was also curious about your experience with sending samples to labs. We paid this inspector $350 per sample (3 air samples and 1 swab) then he also charged us $250 for showing up for a grand total of $1650.

I’m having an issue with post mold testing, the raw count shows 1 stacky inside our remediation area and 0
raw count outside. We are being failed by inspector, does this sound reasonable as we have a total of 6 raw spores of all types inside and 33 outside of all types oly one stacky?
I can’t find any government site with guide to show inspector.
Is this a fair assessment as even he states the area is spotless and surprised at the result, one spore at 75 ml for 5 mins.

You won’t find any government publications that cover the topic of interpreting air samples for mold after remediation. Heck, there aren’t even recognized non-government associations or other groups that have a prescribed.

I think it is most eloquently stated in the Texas Mold Assessment and Remediation Rules (TMARR). These rules state that the criteria for clearance should be established ahead of time, prior to the work beginning. Therefore, you should make the argument that you weren’t notified about a strict clearance criteria.

To answer your question, “Is it a fair assessment”…
I recommend clearance involve taking several samples, not just one inside and one outside. Your interpretation is a function of the type of space we are dealing with. A hospital or home of someone sick should be treated differently than other space types. I think most knowledgeable consultants would clear a “normal” (non-hospital, etc.) space it they find a single Stachy spore in a single sample and all the others are clear. In fact, I know of a top authority who doesn’t get concerned until seeing 10 Stachy spores.

In the absence of government guidelines, everyone is forced to use their professional judgment. Too bad not everyone has good judgment!


Hi Ian,

We had a leak in the ceiling of our 2-story home (coming from a hole in our roof which then leaked through the attic). Our kids were having some coughing and wheezing which we thought might be related so we had some mold testing done. They took 3 indoor samples (one from each level of the home including the basement but none from outside). Here are the results:

A total of 787 S/M3 was reported comprised primarily of Aspergillus/Penicillium @680 S/M3 or 86% of the total

1st floor:
A total of 573 S/M3 was reported comprised primarily of Aspergillus/Penicillium @ 473 S/M3 or 83% of the total.

2nd floor:
A total mold spore count of 98 S/M Aspergillus/Penicillium was reported @73 S/M3 or 79% of the total.

The report indicates that these results suggest there is mold in the basement which is causing elevated levels there and on the first floor. But neither we nor the inspectors saw and mold in the basement and I don’t know what the source of moisture there could be. There’s no obvious moisture down there.

Any thoughts? Thank you so much!

I would trust the visual inspection made by you and the mold inspector over these air sampling results. There are too few samples and no outdoor sample to have conclusive results.
When you do your spring cleaning in the basement, keep an eye out for any moisture stains or mold growth.

Hi Ian,
My wife and I just recently bought a house and with the inspection we did a mold test because my wife has severe allergies and respiratory symptoms. The house is located next to a large wooded area. The test was done by EMSL, and the results were interpreted as low with no need for remediation. the highest counts were: Cladosporium 400/m3 outside compared with 200 in 2 samples from inside, Basidiospores 400 outside and 100-200 inside, Alternaria none outside 50 inside, Aspergillus/Penicillium none outside 50 inside, and Unidentifiable Spores none outside 300 inside. My concerns are: 1: Are these counts low only because it’s winter, does the presence of them now indicate they will be much higher in the summer? 2: From my reading it states counts of 3000 or > are more likely to cause respiratory symptoms in susceptible persons; but there’s no way of knowing if smaller counts can cause symptoms too, are these spores typical of most indoor air samples or could this be because of the wooded backyard? and 3: Why are there 300 unidentified spores in the house and not outdoors is that concerning?
We still have a chance to not buy the house if this is a concern. Thanks for your help!

1. Outdoor mold spore levels vary by season, so this will have an influence on indoor levels.
2. You spore counts are typical from my perspective (although I know very few details of the situation)
3. The spores were unidentified because the lab couldn’t figure out what they were based on what they saw. Air sampling results are highly variable. I would be interested to see the results of a re-test. You may not even see those unidentified spores in a subsequent test.

HI I just had a room tested for mold and the results came back as 50,708s/m3 for penicillin/aspergillus
I am having the wall where I can see the stains removed and treated by a contractor
Do I need this to be done under a contained environment?

YES! You should also strongly consider negative pressure. That means exhausting air out of the work area, ideally with a “negative air machine” (a.k.a. air filtration device, air scrubber).

Hi – Could you give me an opinion on these numbers? We have a shop that has a basement that smells very musty. There have been multiple leaks down there from both a water drain and from toilet back ups. We’re in WA state so it’s pretty damp anyway. In the basement hallway we have Aspergillus/Penicillium at 3,800 count/m3. Total fungi of 4,170.

Without knowing all the details, I can still say that those numbers are relatively high. It’s not enough to just fix the water problems. You also want to clean or remove the water damaged materials. The odor you smell may be from a prior mold problem, or it may be current. I would start by cleaning out the basement and making it shine. Also look for open sump pits which are notorious for making basements musty.

HI Ian

We just bought our first house. I got three air quality tests done two indoor (one first floor, one basement sink area) and one outdoor. The Pen/Asp group indoors came out very high (one 120000 spores/m3, another 150000) with 0 outside. My question is the remediation company did the test by placing the air test machine right next to the mold patch found (one under the sink and one in the kitchen). Both patches are less than 1 square feet. I am wondering if this would inflate the spore counts?


The company doesn’t seem to know the difference between an air sample and a surface sample. I would be VERY cautious when dealing with that company.

Why is the remediation company sampling your air? They should be removing the mold! If they wanted to verify it was mold prior to the remediation, they should have done a surface sample!


Ian, my living room came back with a spore count of 1,222. The room is 18×12. How concentrated is that? The mold generas found present are aspergillius/penicilium, cladisporium, and badiospores. All are non toxic. Does that mean you can’t get sick from it? What is “first colonizer wet mold”?

Hi Ian. Great Site. I am following you on Goggle+ and I hope you can shed some light on my situation.

I recently made an offer on a lake house. The house was a foreclosure that the contractors have completely remodeled. Additionally, no one has lived in the house for more than two years and the air conditioner has not even been installed during this time, let alone run. The home has been closed up (doors and windows closed) for most of these two years.

During the walk-through we saw visual signs of mold but not water marks on the drywall, etc. Just fuzzy stuff on the walls/doors. In the couple of days prior to the mold inspection the sellers cleaned the mold off of the walls/doors and painted over it. I don’t know what they cleaned and/or painted with.

We just received the Mold Analysis Report and it indicates that the upper and lower levels of the home have “elevated” mold levels compared to the outside base samples.

The results are as follows:
Raw/Spores per m3/% of Total
Base – 5 / 200 / 4
Upper – 2 / 80 / 1
Lower – 2 / 80 / 1
Base – 0 / 0 / 0
Upper – 0 / 0 / 0
Lower – 1 / 40 / 1
Base – 0 / 0 / 0
Upper – 1 / 40 / 1
Lower – 0 / 0 / 0
Base – 13 / 520 / 10
Upper – 43 / 1700 / 32
Lower – 8 / 320 / 1
Base – 2 / 80 / 1
Upper – 0 / 0 / 0
Lower – 0 / 0 / 0
Base – 1 / 40 / 1
Upper – 0 / 0 / 0
Lower – 1 / 40 / 1
Other Ascospores
Base – 3 / 120 / 2
Upper – 8 / 320 / 6
Lower – 1 / 40 / 1
Other Basidiospores
Base – 106 / 4200 / 77
Upper – 68 / 2700 / 50
Lower – 41 / 1600 / 4
Base – 3 / 120 / 2
Upper – 11 / 440 / 8
Lower – 1000 / 40000 / 95
Smuts, Myxomycetes
Base – 3 / 120 / 2
Upper – 2 / 80 / 1
Lower – 4 / 160 / 1
Base – 1 / 40 / 1
Upper – 0 / 0 / 0
Lower – 0 / 0 / 0

The report minimum detection limit is 1 raw count and 40 Spores per m3. The comments include “Debris: Heavy” for the Upper Level, “Penicillium/Aspergillus too numerous to count” for the lower level and “Debris: Moderate” for the Outside test.

I am most concerned about the Cladosporium, Other Ascospores and Penicillium/Aspergillus since those results are greater than the outside (base) sameple. Are these results more consistent with water damage or with a “sealed up” house with no air conditioner even hooked up?


Hi Ian, we had a burst water pipe which ran for 3 weeks flooding our home with 300,000 litres of water while we were on holiday.on returing we found mould growing is every room. we had air samples taken which showed 16,500 CFU/m3 wheras the outside had between 1,300 and 2,840 CFU/m3 but importantly it was of a different species to the inside, showing that the contamination internally was from an internal sourse. my question is – how dangerous is this internatal level of 16,500? Regards Quintin

What type of mold was present? Personal sensitivity varies so widely that it is not possible for me to say how much is “dangerous” to you. How many peanuts are dangerous? For some kids, just 1. Other kids could eat thousands! Although I don’t know if 16,500 is dangerous for you, I can say with some confidence that those levels are not normal. Find the mold, fix the moisture, remove the growth, and clean the air & surfaces!

Hi Ian,
We recently had a small leak that effected our HVAC and minor ceiling water damage. I had a mold report prepared, but can’t get anyone from the company to give me straight answer on the following.
The only spore count to come back high was Chaetomium at 510/spores m3!

I’ve had a few outrageous quotes to mediate this. Is this spore count dangerous

Hi Ian,

I live in an apartment in the south Florida area and recently it was discovered after most of my family becoming ill, that the dryer duct work inside the wall space was not maintained or constructed properly and had been discharging all of the lint and moisture into the wall space, for what appears to have been at least 2 or more years of accumulation. There is present evidence of moisture damage on some areas of the wall, but no obvious signs of mold growth on the drywall. I was informed by a Licensed building inspector that the lint buildup could potentially be a place for the mold to grow as there was large amounts within the wall. I had a mold inspector come out and received the test results back today showing that from an inside air sample taken there was 1 count of 13 CTS/M3 (100%) of an unspecified spore. The outside sample did not have any findings of an “unspecified spore”. Should I be concerned with the findings? Both of my children (ages 2 and 3) had blood work done after a visit to the ER last week and tested positive for Mycoplasma.

You don’t ever want to find MOLD in a building you are renting in an Apartment complex in VA: Our complex paid a carpet guy do a test he went to Pro-Lab with his Petri Dish & found NOTHING in my HOME and that TEST is how the Apartment will deal with treating my family & our HOME. I hired a Pro he Did air quality every level of the HOME and swab & found
Ascospore 400
Aspergillus/Pencicillium 1,200
Basidiospores 200
Chaetomium 100
Cladosporium 1,900
Stachybotrys 200

He found with thermo camera leak’s under ground we could not see coming into my house the level of Stachybotrys in our room was over 3,000 AND sadly the county inspector can not help us because of the damn law’s in VA.

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