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Dr. Jackson Kung’u (PhD)- Mold Specialist.
Phone: 905-290-9101
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Indoor Air Quality

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.

Aspergillus/Penicillium in the Basement

Question: Is Aspergillus/Penicillium spore count in the basement high? We have this smell in our house for some time. We have also arranged for the gas company to come to see if there is gas leak. Last week, we had an air sample taken from our house. The Aspergillus/Penicillium reading from outside was 267 spores/m3 and the reading from the basement was 26,667 spores/m3. I do not know if these readings indicate any significance. Do you have any suggestions for the cause and solutions? Thank you very much for your help.

Answer: I think the Aspergillus/Penicillium spore count in the basement suggests persistent humid conditions. You may want to hire a professional to come and assess the extent of mold growth in the basement, identify the cause (i.e., moisture source) and suggest the best method to fix the moisture problem and remove the mold safely. To control the growth of mold such as Aspergillus/Penicillium the humidity in the basement has to be reduced to a level below 60%. The following techniques can help control moisture in the basement:

  1. Fix leaks, drips, and seepage problems.
  2. Dry wet areas within 24 to 48 hours to prevent mold growth. Thoroughly clean and dry water-damaged carpets and consider removal and replacement of items that appear to be permanently water damaged. Mold and mildew on hard surfaces can be washed and the surfaces dried completely.
  3. Do not finish a basement below ground level unless all water leaks are sealed. A finished basement should also have adequate outdoor ventilation and heat to prevent condensation.
  4. Operate a dehumidifier in the basement, if necessary, to keep relative humidity levels down. But keep in mind a dehumidifier can be expensive to operate.

Molds In Basement

Both finished and unfinished basements tend to be damp and hence prone to mold growth. Molds in basement are predominantly influenced by chronic moisture problems, such as window well leakage. Whether a basement is occupied or not, growth of molds in basement is a health hazard since the spores tend to move upwards to the living spaces. It has been established that basements could be the predominant sources for mold spores in both summer and winter. When people who are susceptible to mold inhale the airborne spores they react to the proteins in the wall of the spores.

How do you know you have molds in basement?

You know you have molds in basement when you smell the “musty” odor or see small black, bluish or white spots along the basement walls. The mold spots may be fuzzy or look raised. Mold growth will occur on any organic or porous materials including paint, cardboard, newspapers, wood, textiles, and carpet that are exposed to moisture. You may also find molds in basement growing on dirt or dust trapped on fiberglass insulation. Mold growth may also be visible on wooden studs and rafters.

How to control molds in basement

Elimination of moisture is the most effective method of mold growth control. To eliminate moisture problems in the basement may involve foundation damp-proofing, fixing grading problems, providing adequate on-lot drainage systems, and sealing areas of moisture ingress. Also remove excessive internal moisture sources in the basement (humidifiers, cooking) and ventilate other sources (clothes dryer, bathroom). If condensation in the summer is the problem, it’s recommended that you do not ventilate the basement directly with warm, humid air. Ventilation through an air conditioning system or with a desiccant-type heat exchanger is recommended.

If you have molds in basement call 905-290-9101. We may be able to help you or direct you to people who could help you.

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.