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Dr. Jackson Kung’u (PhD)- Mold Specialist.
Phone: 905-290-9101
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air sampling

Evaluating Mold Contamination In A Building

Question: If I want to evaluate mold contamination in a building, should I use air sampling of molds or ergosterol in dust?

Answer: The method to use to evaluate mold contamination in a building depends on the objective of the investigation and the resources available for the investigation. First let’s see what kind of data each method yields.
  • Air sampling For Mold

There are 2 methods currently used for sampling for airborne spores. These are air sampling for total fungal spore count (also referred to as nonviable analysis) and air sampling for culturable airborne fungal propagules (commonly referred to as viable analysis). The data obtained by the nonviable analysis are number of spores (or fungal elements if you include other fungal structures) per cubic meter of air. Viable analysis gives colony forming units (CFU) per cubic meter of air. Each of these 2 methods has it’s advantages and disadvantages. For example since non-viable spore analysis depends on the morphology and sizes of spores alone, identification is limited to only a few groups of fungi that have spores with unique characteristic. A vast majority of spores are reported as unidentified since it’s difficult to tell which group of fungi produced them.

The major advantage of nonviable analysis is that since the analysis does not depend on the viability of the spores, all spores present in the sample can be counted whether they are dead or alive. This brings us to the major disadvantage of analysis. If 95% of fungal structures contaminating the air were dead, this method would detected only 5% of the contamination.

The advantage of culturable sampling is that the recovered molds could be identified to species level. This is important because some important characteristics such as production of mycotoxins or pathogenicity are species (and sometimes strain) specific.

Given the advantages and disadvantages of the 2 air sampling methods, an investigator has to decide which method to use. In some cases, using a combination of the 2 methods is recommended.

  • Dust Sampling For Ergosterol

Ergosterol is the major sterol in the cell membranes of fungi (yeasts and mold). It’s present in mycelia, spores, and vegetative cells. There is a strong correlation between ergosterol content and fungal dry mass. Ergosterol content has, therefore, been widely used as an estimate of fungal biomass in various environments, such as soil and aquatic systems. Ergosterol measurements have been proposed as a new method for determination of total fungal biomass in investigations of indoor environments. One limitation about this method is that the amount of ergosterol in fungal tissue is not constant and varies with fungal species, age of the culture, developmental stage (growth phase, hyphal formation, and sporulation), and growth conditions (growth media, pH, and temperature). Another limitation is that ergosterol measurements cannot be used to determine the species present in the dust sample since it’s not genera or species specific. The method is currently not widely used and very few commercial laboratories have the capability to analyze for ergosterol in dust.

A Useful Ergosterol Reference

ANNA-LIISA PASANEN, KATI YLI-PIETILÄ , PERTTI PASANEN, PENTTI KALLIOKOSKI, AND JUHANI TARHANEN (1999). Ergosterol Content in Various Fungal Species and Biocontaminated Building Materials. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Vol. 65, No. 1: 138–142.

Quick Take 15

Question: How long is the time needed by Quick Take 15 apparatus for detection of mould? Is there any incubation time needed after the sampling step? Or is the detection system different from culture followed by DME. In fact I am looking for a rapid detection system for Cladosporium.

Answer: Quick Take 15 is used for collection of air samples for fungal spore counting and identification. It’s designed for short sampling times (1-15 minutes) for airborne particulates including mould spores. It’s ideal for use with Air-O-Cell, VersaTrap, and Allergenco cassettes. Samples collected with quicktake 15 do not require incubation and hence you could use it for rapid detection of airborne spores and other particulates. Results can be obtained within the same day.

If you require identification of the moulds to species, then you need to use Quick Take 30. Quick Take 30 uses agar plates. After sample collection, the samples are sent to a laboratory for incubation and species identification and enumeration. It takes between 10-15 days (or more) to get the results.

MBL is using ASTM D7391 – 09 Standard Test Method to Analyse Non-viable Air Samples

Mold & Bacteria Consulting Laboratories (MBL) inc., is now using the new ASTM method D7391-09 for analysis of non-viable air samples. Until recently, there has been no standard method by which to analyze non-viable air samples collected by inertial impaction samplers such as Air-O-Cell, Allergenco-D, micro 5 and other similar samplers.

The American Society for Testing Materials (ASTM) International published the new standard method, D7391-09 entitled “Standard Test Method for Categorization and Quantification of Airborne Fungal Structures in an Inertial Impaction Sample by Optical Microscopy”.

The method outlines two procedures for enumerating fungal structures: one for slit impaction samples such as air-o-cell and allergenco-D and the other for circular impaction samples such as micro 5. Analytical results are presented in fungal structures/sample (fs/sample) and fungal structures/m3 (fs/m3)

For details regarding the standard, please visit the ASTM website. For analysis of your samples using the standard method please contact us by Phone:

Toronto: 416-628-0238
Mississauga: 905-290-9101
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Vancouver: 604-484-9114
Winnipeg: 204-272-3752

Toll Free: 1-866-813-0648

Or you can contact us by:
Fax: 905-290-0499

Air sampling for Airborne Mold Spores

Question: I’ve looked at the report and I’m very surprised. There is hardly any results. Have I done something wrong when I did the air sampling?

 We had a company selling air cleaners offer to test our air. They did air sampling for for two viable air samples. Then they said we had Aspergillus versicolor. Is it possible that a mold will show up on a viable test and not on a non-viable test?

Thank You

Answer: I don’t think you did anything wrong in your air sampling. The analysis of the air samples indicated there were some mold spores in your house BUT that is normal for almost every home. Air in every home or building is highly likely to contain some amount of mold spores and other fine particulates. Therefore, air sampling is not used to determine whether there is mold in a building but it is rather used to determine the amount of mold spores present in the air. The reason why one would want to know how much mold is there is because it’s the amount and the types of mold that the building occupants are exposed to that matter.
 
The air sampling you did and the one that other company did are different in many aspects and hence results from the two tests can be difficult to compare. Unlike the viable sampling method, the test you did does not allow for identification of moulds to species. That’s why we did not report Aspergillus versicolor. However, this method generally gives a better idea of how contaminated the air is because identification and enumeration of spores does not depend on whether the spores are viable (i.e., alive) or not.
 
I would like to know a little bit more about the viable air sampling conducted by the other company. Did they use an air sampler or just opened the agar plates and left them open for some time? The latter (called the settle plate method) is generally not a very efficient method for air sampling but it’s less expensive to perform and can at times provide useful information regarding the air quality in the home. The second question is, if they used the settle plate method, how many colonies were reported and how long were the plates exposed? The amount and not the presence is very important when it comes to indoor molds. Aspergillus versicolor is one of the most common molds indoors and presence of a few spores/colonies is not an indication of a mold problem. If you have not experienced any moisture problems in your home, it’s very unlikely that you have a mold problem worth worrying about.

As to whether a mold can show up on a viable test and not on a non-viable test, yes, it’s possible.

Culturing of indoor mold

Question: I have a question concerning mold in a home that will be put up for sale. There was a general test for mold done and we were told we had a high level of Aspergillus/Penicillium but not what type of either of these. After doing some research we realized that this did not tell us if we had one of the more toxic varieties or not and are wondering if we could get these cultured to determine the type of these we had. The test done was an air sample. The count in one area of the home was 4,960 spores per cubic meter of air. Please advise as to the best course to follow for culture.

Answer: For the purpose of selling the house, you possibly don’t need to culture the mold to know whether it’s toxic or not. All molds are a potential health hazard and should not be allowed to grow in buildings occupied by people. I would suggest you get a professional to thoroughly check for any hidden mold and/or water issues that require to be corrected.
 
Culturing of indoor mold is only necessary if you want to determine the specific types of molds present in the air (and if still viable). Although culturing is also recommended in situations where occupants complain of ill health which they suspect to be associated with mold, it does not prove that the mold is the cause of the sickness.