Dr Jackson Kung'u- Mold Specialist

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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.

Cost of testing air for mold

Question: My question regards the cost of testing air for mold. I have mold problems in two closets in my home and in a couple of corners in the house. I also get alot of moisture build up at the bottom of my windows that has also caused some mold. At the beginning of the year I installed a Conservation voltage regulation(CRV) unit on my furnace but as winter is coming again the problem still seems to be there and I think my daughter is experiencing health problems over this. My home is only 11 years old. How much does testing air for mold usually cost?

Answer: Testing air for mold is very simple and does not have to be expensive. A homeowner or property manager can save money if they could initially test the air themselves before calling in a professional. This does not mean that a professional is not required for testing air for mold but should only be hired to resolve complex problems not simple air testing.

For most people, testing air for mold themselves (using the same tools used by professionals) in their homes is all they need to identify if mold is present in excessive amounts.

Testing Air For Mold

Settle agar plate

Testing air for mold may involve any of the following methods:
  •  Settle Plate Method: This method involves exposing agar plates to the air in the room or rooms to be tested. The agar plates can be exposed for a duration of 1-4 hours and then covered and shipped to a laboratory for mould counting and identification. The cost of this test is very low. However, since this method is not very efficient in terms of air sampling, it’s not generally recommended.
  • Andersen Air Sampling Method: This method is similar to the settle plate method but instead of opening the agar plates and leaving them for airborne spores to settle on the agar by gravity, the method utilizes a pump to impact the air onto the surface of agar. Since the air is drawn into the agar surface (similar to how we draw air into our lungs) the method is very efficient. This method requires the person doing the sampling to be trained in aseptic techniques since it’s very easy to contaminate the agar plates and subsequently ending up with false postives. Since, it requires training and experience in aseptic techniques, it’s not recommended for non-professionals.
  • Non-viable Air Sampling Method: This method involves impacting air on an inert sticky surface using a special air pump. The method is very efficient in sampling for airborne particulate. The method does not require any special training other than following the instructions on how to fit the sampling cassette onto the pump and how to switch the pump on.

Non-viable Air Sampling Method

The pump’s “flow-rate” is set (“calibrated”) to draw a specified volume of air – for a specified length of time (usually 5 or ten minutes) – through the filter. The sample is later examined in the laboratory under high magnification to identify and count mold structures – dead or alive. This is important as dead (‘non-viable’) mold spores can cause allergy problems, too.
 
Molds are a normal part of our environment both inside and outside our homes. And, as most buildings are ventilated with outdoor air, any particulate contained in the outdoor air including mold spores, dust, pollens and other pollutants infiltrates inside the buildings. Testing air for mold gives us an idea of how much airborne mold spores people are exposed to.

 To determine whether the spores inside the house originated from outside or are from mold growing inside the house an outside air sample is collected for reference.

Testing air for mold. QuickTake 15The other air samples are taken indoors from each room that requires to be tested. When the laboratory receives the air samples the number of collected mold spores is counted. Although there no set permissible levels of airborne spores (i.e., save or unsave levels), a normal, healthy indoor environment can be defined as one where:
  •  Species or types of mold spores that are found on the inside air sample are also found on the outside air sample – this is referred to as normal ‘mirroring’ or ‘trapping.’

However:

  • The number of mold spores found inside the house or building should not be greater than the number of mold spores found outside. Also, the types of mold spores present in the inside air should be similar to those found in the outside air. Some types of mold spores when detected inside (and not outside) even in very low levels could indicate a problem. For example a few spores of Chaetomium, Stachybotys, Ulocladium, and Fusarium are indicative of excessive moisture in the building and possible hidden mold growth. In this case a professional would be required to perform further investigations to locate hidden mold growth if any.

Doing Your Own Air Testing For Mold:

It’s fun doing your own air testing and it’s easier than vacuum cleaning the carpet or doing laundry.

For more details, click Mold Testing Kit or call 905-290-9101 for more information.

How To Test For Mold

Mold testing has 2 components:

  • Assessment of the extent of mold growth in the building
  • Laboratory testing of the samples collected during the building assessment

Assessment of the extent of mold growth

This component of mold testing is very important because the results of this assessment are used to determine the level of remediation required. Mold assessment in a building should be performed by a qualified professional.

Laboratory Testing Of Samples

Laboratory testing of samples for mold is necessary especially in situations where mold is suspected to be the cause of illness to the building occupants. The samples tested for mold include the following:

  • Bulk and Surface Samples: These include samples such as pieces of carpet, carpet dust, drywall, wallpaper, swabs, tape lift samples or any other material suspected of mold contamination.
  • Air Samples. Air samples may be collected on culture media or on inert non-culture media depending on the objectives of the mold investigation.

Contact Information

Dr. Jackson Kung'u, PhD.
Phone: 905-290-9101
Fax: 905-290-0499