Fungi Testing for Indoor Environment

There is no one test that can provide a complete picture of an indoor environment.

Rather, we rely on the expertise of Indoor Air Quality (IAQ) professional in the field and a variety of tests that tell a story about the environment and any conditions that the occupants may be encountering. Whenever possible, it is always recommended that one consult with an IAQ professional to perform a comprehensive mold investigation. When that is not possible, a Do-It-Yourself mold test kit may be the best first step in helping to determine if you have a mold problem.

One of the most standard and prevalent indoor air quality tests performed by IAQ Professionals utilizes the spore trap air cassette.

Spore Traps

Spore traps can provide a baseline before remediation, clearance after remediation or provide an indication of the current load of fungi and particles in an occupied space. Generally, a combination of spore types along with an analysis of particulate is an important piece of information in an investigation which spore trap cassettes can provide.

Tape Slides

Tape slides are used for one main purpose – suspect mold growth on hard surfaces. When visible suspect mold-like growth is seen on drywall, leather, cardboard or wood, the tape slide is pressed on the suspected fungi to collect a sample. The laboratory will be able to identify the fungi, generally to the genus and sometimes the species level. This is valuable information, not only to confirm if the suspect growth is indeed mold, but also indicates the initial source of mold. Increased concentration of mold spores in the air, as identified in spore trap cassette sampling, occur because there are colonies of mold occurring on surfaces.

Viable Fungi Culture Identification

In addition to spore traps and tape slides, culturable samples can be very useful to IAQ professionals. The most useful samples for culture will come from inhabited carpeted areas. Carpet harbors not only living organisms, but also contains dust mite detritus which allergists tell us is the number one trigger for asthmatic reactions. Dust mites proliferate at RH above 55%. Not so coincidently, fungi and bacteria do, as well.

Dust collection cassettes are available that fit most vacuum cleaners. The laboratory will sift the dust to get uniform small dirt particles that can be placed in a buffer solution and spread plate onto petri dish agars of Cellulose, DG18 and Malt Extract 2%. Each type of plate recovers a different set of organisms and all of them together give us a very good picture of the history of the indoor environment. The fungi are identified to the genus level except Aspergillus and Penicillium where it is very important to identify to the species level.

Swabs

Have a hard place to reach? The swab is probably the best tool. Above surface analysis can be a useful comparison with spore traps and carpet dust samples. This generally entails using the swab to collect the sticky build up that resides on the top side of ceiling fans or supply and return registers / vents.. The swab will be placed in a buffer and plated on the agar plates noted above.

So far, we have only addressed the sampling for fungi. When the variety of samples are combined, we generally get a very good picture of the microbiological environment. With the expertise of the investigator and the laboratory, problems are quite often identified. However, depending on the property’s history or occupant complaints, an IAQ professional my also want to perform bacterial testing.

Swab test

So far, we have only addressed the sampling for fungi. When the variety of samples are combined, we generally get a very good picture of the microbiological environment. With the expertise of the investigator and the laboratory, problems are quite often identified. However, depending on the property’s history or occupant complaints, an IAQ professional my also want to perform bacterial testing.

Bacteria

Certain species of bacteria play a very important part in respiratory distress and even pneumonias. Most healthy individuals are not affected by bacteria in an indoor space but people who are immunocompromised, elderly or stressed enough that the immune system is not responding properly, are at risk.
Potentially, the most risk in a home is in our fresh water systems. Plumbing has “elbows”. These are small areas in the pipes where water settles when it is not being pulled through. When common fresh water bacteria attach in the elbow areas, they lay down a protective biofilm that allows for a reservoir where millions of bacteria will multiply. This is a common situation in homes that do not have whole house water filters. The other area where slime will accumulate is the shower head. When the shower is activated, a fine mist can be inhaled and there is a possibility that millions of bacteria are being inhaled into the deep recesses of the lungs. When these bacteria are Pseudomonas aeruginosa or Legionella pneumophila, there is a potential for bronchitis, flu like symptoms or pneumonia.

By using a specially prepared swab, you can unscrew the shower head and swab inside the pipe and the rear of the shower head where it attaches to the pipe. The laboratory will place the swab in a buffer and plate the contents to test for Legionella pneumophila.

These are not the only tests, but rather, the most common tests needed to evaluate an indoor environment . Consult a professional investigator or the laboratory for a sampling plan that matches your needs.

Richard Billups
Microbiology Manager
Air Care Laboratories

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