What Home Inspectors Should Know about Indoor Air Quality

Man with a nose and mouth mask holding a sign Fresh Air.

Indoor air quality is important in a home.

Indoor air quality can play a big part in the quality of life. Whether it be the office, your home, or your neighborhood, the air you breathe has to be clean enough so that you remain healthy and functional.

Much can get in the way of this goal. Mold, radon, VOCs, CO, CO2 and more in a home can affect the health of its inhabitants.

As building materials and practices improved over the years, more houses were built that are considered “tight” — not much air gets in or out. These homes are well-built, well-insulated, and energy-efficient. But they also might be full of noxious gases.

Although the ASHI standards of practice say that home inspectors are not required to determine air quality, you still should be familiar with air quality issues so you can flag signs of a problem. You may then want to refer the potential homeowners to a professional who can test for toxic substances in the air. Or, you may want to learn how to do this yourself and offer it as an add-on service.


Mold is one of the most common causes of poor air quality. It grows quickly and easily under the right circumstances. Homes in humid locations are particularly vulnerable.

Mold needs moist, dark conditions to thrive. Dryness and sunlight kill mold. This is why it is so frequently found in basements. Leaks, drips or damp areas under sinks or near appliances such as clothes washers and water heaters create perfect conditions for growing mold.

Easily identified by the black and brown stains it leaves on ceilings, walls, floors, carpets and household items, mold can release spores into the environment that can cause cold or flu-like symptoms or worse. Musty odors are another telltale sign of mold.

However, mold can be present inside walls or in other areas that aren’t readily visible, so don’t assume if you can’t see it that it isn’t there.

Mold on a wall and ceiling.

Mold in a home can seriously compromise air quality.


Radon is a gas that occurs naturally in the earth and can seep into homes through cracks in the foundation or gaps around pipes. It’s colorless, odorless, and tasteless, so there are no signs to be detected.

The only way to determine if a house has unacceptably high levels of radon is with a test designed specifically for this purpose.


VOCs, or volatile organic compounds, are dangerous gases that come from thousands of household products, including building materials, paints, varnishes, cleaning products, perfume, hairspray, printers, and more.

Sometimes VOCs give off an odor. Paints, varnishes, and cleaning products often have an odor. Clothes that have been dry cleaned and have a chemical smell may not be safe. Any item in the home that smells “new” — shower curtains, linoleum, carpeting — is suspect.

The older an item is, the fewer VOCs it gives off. So an airing of the home that has had recent installations might be all that’s needed. But if the occupants’ health suffers, they may want to get their air tested. The Environmental Protection Agency says symptoms include a headache, nausea, confusion, fatigue, and dizziness.


We naturally exhale CO2, so levels can rise when a home is crowded, such as during parties or holiday gatherings. Other causes of rising CO2 levels include a malfunctioning air conditioning unit and the burning of fossil fuels in the home.

Carbon dioxide is also odorless, colorless, and tasteless. The only way to determine if CO2 levels in the home are a problem is with a test.


If carbon monoxide builds up in a home, it can kill the occupants. Buildups are usually traced back to a malfunctioning furnace, but they can come from other sources as well, such as fireplaces, attached garages, gas and wood stoves, and more. CO detectors are a common part of many households today. If the home you are inspecting doesn’t have one, recommend the homeowners get one. Most are about $30 and can mean the difference between life and death.

ICA School’s inspection training course offers home inspectors the opportunity to get certification in mold and radon inspection — free.   Enroll now and get your inspection training for the best value.

Comments are closed.