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Dr. Jackson Kung’u (PhD)- Mold Specialist.
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Mold Testing

Air Quality Test Showed No Mold But Can See Visible Mold

Air quality test is often conducted to determine the level of airborne mold spores. Interpretation of air quality test results is often difficult as the levels of mold spores in the air vary greatly depending on the activity in the room, changes in temperature and relative humidity, ventilation rate and season of the year. During summer for example, indoor mold spore counts can be relatively very high even in homes with no visible mold growth due to infiltration of spores from outdoors.

It’s also possible to have very few airborne spores in buildings with visible mold growth. This is because there are biological differences between the fungi in terms of the way they produce their spores. The Aspergilli and Penicillia, for example, produce large quantities of dry spores that easily become airborne. On the other hand, Fusarium and some species of Stachybotrys (black mold) produce moist spores that are not easily released into the air. Some other molds such as Chaetomium and Phoma produce their spores in enclosed structures (fruiting bodies) and hence these spores may not be detected by air sampling until later when the material dries out or is broken on impact e.g., during renovation.

For viable samples, the spores and fungal materials present in the air may be dead or may belong to molds that cannot be cultured in artificial media. The mold may also be alive but may not be culturable on the detection media used. Therefore a combination of air sampling (both viable and non-viable), surface (e.g., tape-lift) and bulk sampling is recommended. An air quality test alone is not enough to rule out mold growth. See the article Non-viable Fungal Air Sampling Alone May Not Be Adequate.

Indoor Air Quality – Testing For Mold

The health effects of poor indoor air quality are dependent upon several factors including the type of contaminant, concentration, duration of exposure, and individual susceptibility. Indoor air quality can be compromised by a number of contaminants including mold.

Assessing the status of Indoor Air Quality

The status of indoor air quality is assessed by measuring the levels of contaminants indoors. These Contaminants include:
1. Biological contaminants such as mold, bacteria, viruses, etc.
2. Chemical contaminants such as formaldehyde.

This article is focusing on mold as an indoor air contaminant. Contamination of air by mold spores can easily be determined by air testing.

Testing Air for Mold

There are two methods commonly used to test air for mold. These are:
1. Viable or culturing air testing

2. Non-viable or total spore count air testing.

Assessing the Status of Indoor Air Quality by Viable Air Testing.

For viable air testing, air sampling can be conducted in two ways. The first method uses settle plates. This technique involves opening agar plates inside the area being tested and leaving them open for half an hour or more. Airborne mold spores and hyphal fragments settle by gravity onto the agar plates. Any viable spores or hyphal fragments would then grow into visible colonies that can be counted and identified. A high colony count is an indication of poor indoor air quality. This method is cheap since all it requires is agar plates. However, it’s not an efficient way of testing for mold spores in the air. The second method uses an air sampling pump. In this case, air is impacted onto the agar plates by a pump. This method is more efficient since it doesn’t depend on free-falling of spores into the agar. Viable testing for mold has a big disadvantage in that it only detects viable spores/hyphal fragments yet even dead spores are a health hazard.

Assessing the status of Indoor Air Quality by Non-viable Air Testing.

Non-viable air testing samples are collected by impacting air on an inert surface coated with an adhesive. Most of the spores and other particulate in air get stuck on the adhesive surface. The samples are then tested by direct microscopy. The spores and/or other particulates are enumerated and identified. The results are reported as spores per cubic meter of air. This method of sampling requires an air sampling pump such as BioPump and air sampling cassettes such as Air-O-Cell or allergencos. The major advantage of this method is that both viable and non-viable airborne spores and other particulates are enumerated thus giving us a better idea of the status of the indoor air quality.

Air Quality Mold Testing Kits

Air quality testing should be conducted by a qualified professional. However, there are basic tests that a homeowner or a property manager can perform by themselves and save money. Air quality testing for mold does not require any special training. Mold & Bacteria Consulting Laboratories has been renting air quality testing equipment to homeowners, property managers or professionals who are just starting their businesses.

To perform your own air quality testing for mold it’s important to plan ahead. For example you need to decide how many rooms you want to test as this will determine the number of air samples you will collect. ideally, one should test all the rooms but if the budget cannot allow you can test areas of concern. In addition to the samples you collect from indoors, an outdoor sample is also required. The outdoor air sample helps to determine which of the mold spores detected indoors had likely originated from outdoors.

Interpreting air sample results can be difficult. However, after comparing indoor samples with outdoor sample, if the types of spores detected from the indoor sample are the same as those detected from outdoors and the indoor counts are significantly lower than those of the outdoors, then we can conclude that the tested areas had no mold problem at the time of testing. This conclusion is only valid if we cannot visually see mold growth and the building is not damp. It’s important to note that while the spore counts could be low, presence of certain types of molds could be an indication of major moisture damage and possibly hidden mold growth.

 How to perform air quality testing

As indicated previously you’ll require to rent an air sampling pump. You’ll also need to purchase air sampling cassettes. Mold & Bacteria Consulting Laboratories provides instructions on how to operate the pump. After sampling the samples are sent to the laboratory for identification and counting of spores. The results are reported as the number of spores per cubic meter of air. Click air sampling instructions to watch a video on how to perform air quality test for mold.

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.

Stachybotrys

Question:  Hello there. I work in a boat and recently we discovered that we had a lot of mould on our ceiling. A company came and tested the mould and it came back to be Stachybotrys or some thing similar (sorry about the spelling…). They are planning to clean the area with air cleaners and filters etc. They say that the mould is only in two of the five crew rooms and nothing in the other rooms. Is it possible to have mould so confined, or is this just my superior’s explanation. Also, I have been living here for the past year. What effect can this mould have on me? Should I be worried about any thing..?? Thank you for your help…, It’s always hard to know the truth when you work in a boat. Every thing goes through the captain, and he decides what we should know.

Again thank you for your time.

 Answer: Yes, it’s Stachybotrys or what the general public refers to as black mould. As, to whether mould can be confined to some areas, yes, it can. Generally, mould, and especially the type that requires excessive moisture such as Stachybotrys will only grow in those areas that are extremely wet.

If you’re not feeling sick, I would think there is no need for you to be worried. Not everybody is susceptible to indoor mould. Also, the effect of indoor mould is only likely to persist if an individual who is susceptible to mould continues to be exposed. Exposure to molds such as Stachybotrys is mainly through inhalation. Fortunately spores of Stachybotrys do not become airborne easily unless they are disturbed.