IAQ Testing – What Does It Mean?

Sep 17, 2018

IAQ Testing

We often get calls from clients asking for indoor air quality (IAQ) testing, and when asking if they have specific concerns they will often reply with “I want to test for everything”. The problem is, air quality is a huge field! Similar to the phrase “medical testing”, it would be impossible for your doctor to test you for everything. For most residential concerns, IAQ testing can be broken down in the three main categories; chemicals, bioaerosols, and particles.


Chemical testing is probably the most broad of the three IAQ testing categories. It can range from volatile organic compounds (VOCs), radon gas, carbon monoxide, sewer gas, and more. Just in the category of VOCs we are talking about a group of over 10,000 compounds! Common contaminants like total VOCs, carbon dioxide, and carbon monoxide can be measured with sensitive handheld instruments. For other contaminants like formaldehyde, specific laboratory testing needs to be done. One challenge with chemical testing is we can only measure what we are looking for, so if the issue is being caused by something very unusual, it may go completely undetected. This is why we take great care in talking with the client about their issues, and only suggest testing that we think will help figure out the issue.


Bioaerosols are a class of airborne contaminants that come from living things. If we break down the word bioaerosols into its ancient Greek roots we have the parts bio – life, aero – air, and sol – solution. Common bioaerosols in the built environment are fungi (e.g. mold), bacteria, and allergens.

The most common fungi in the indoor environment are molds- fungi which grow filamentous structures called hyphae and produce spores. Mold growth on building materials is limited to the amount of available moisture, meaning if the indoor environment is dry and free from water or excess humidity, mold won’t grow. Once water is introduced into the indoor environment, mold can begin to grow using nutrients in building materials, dust, and debris around the home as a food source. There are a few different ways to assess the indoor air quality for mold, but the most common is done using non-viable spore trap cassettes. You can read more on mold testing in our numerous blogs on the subject.

While mold affecting indoor air quality comes from growth on building materials, bacteria in the indoor environment mostly comes from the human inhabitants in the building. Every cough or sneeze can release a plume bacteria into the air. However, the most notorious indoor bacterial bioaerosol is Legionella, which doesn’t come from other people. Legionella is a waterborne bacteria that grows in warm water (such as hot tubs, decorative water features, cooling towers, etc) that can become aerosolized and cause infections in humans if they are exposed.

Some other ways bacteria can affect the indoor environment are sewage backups, pest infestations, or biohazard (blood and other bodily fluids) situations. Testing for bacteria is always dependent on the suspected source. Sewage backups would be tested for fecal bacteria, whereas Legionella testing would be done with a water sample from suspected sources.


The final category of IAQ testing is particles. Particles in the indoor air can be assessed generally based on size, for example PM 2.5.  Or they can be based on what materials make up the particles such as asbestos or respirable crystalline silica. General particulate levels can be assessed based on their aerodynamic diameter, expressed in micrometers (aka microns). Common sizes are PM2.5 and PM10; the smaller the particle size the deeper into the respiratory system they can be inhaled, and thus have a greater health concern https://www.epa.gov/pm-pollution/particulate-matter-pm-basics . This type of testing does not identify the makeup of the particulate matter, only the size. Specific materials like asbestos and crystalline silica have specific health concerns, and should be monitored when appropriate.

Asbestos was used in many materials, and when those materials are disturbed the asbestos fibers can be released into the air. Asbestos exposure can cause lung cancer, and whenever there is potential asbestos containing materials present the correct precautions should be taken. Respirable crystalline silica has a similar concern to asbestos. Crystalline silica can come from many sources such as sand, granite and other minerals. When these materials are worked into a respirable size via grinding, blasting, drilling, etc they pose a hazard to human health. Crystalline silica is a lung carcinogen and can cause silicosis, scarring of the lung tissue from silica inhalation.

This blog is really only scratching the surface of indoor air quality testing. Each air quality concern is unique and can pose its own special challenges. If you have an air quality concern and would like to discuss with us your options for IAQ testing, please give us a call!