Air quality outdoors has been a global issue for decades and has led to governmental actions such as the Clean Air Act and to broad citizen activism. Indoor air quality is a more recent issue taken up both by environmental activists and homeowners concerned for their health. Increased interest in indoor air quality is due to heightened awareness and also to various trends that may result in greater trapping of pollutants inside and/or likelier development of problems such as toxic mold.

Degraded air quality, whether indoors or outdoors, affects people in different ways and to different degrees. Some people react to pollutants after a single exposure while others react only after repeated exposures. Sometimes reactions are immediately apparent; other times they emerge only after a significant delay. But regardless of your individual sensitivity, it is worthwhile understanding what can affect indoor air quality. Let’s make a home inspection checklist of the various contributors to poor or degraded air quality.

Combustion Byproducts

Smoke from burning tobacco is probably the most prevalent detriment to air quality. Whether direct or secondhand, tobacco smoke can cause cancer and serious respiratory illnesses. Secondhand smoke has an especially harmful effects on children, tending to increase the number of asthma attacks, lower respiratory tract infections in children under the age of eighteen months, and respiratory tract infections resulting in hospitalization. Tobacco smoke can also generate carbon monoxide and/or nitrogen dioxide.

Other combustion byproducts that degrade air quality come from un-vented or improperly vented fuel-burning appliances. Pollutant type and amount depends on appliance type, installation, maintenance, ventilation, and fuel. The two most common combustion pollutants are carbon monoxide (CO) and nitrogen dioxide (NO2). Both are colorless and odorless gases that don’t just lower air quality but seriously affect human health.

Carbon monoxide interferes with oxygen delivery throughout the body. It may result from un-vented kerosene or gas space heaters, leaking chimneys or furnaces, back draft from gas- or wood-burning appliances, and auto exhaust from an attached garage. Nitrogen dioxide tends to cause irritation in the ears, nose, and throat, shortness of breath, and increased risk of respiratory infection. It tends to result from un-vented gas or kerosene stoves or heaters.

Green and Efficiency Trends

Comparing an overall house inspection evaluation today with one made twenty years ago would reveal trends that typically reduce air quality. These include the use of heavier insulation and making the house more airtight, which raise comfort level and save energy, but these practices also decrease infiltration and natural ventilation. The air can then take on a stale quality.

We saw above that combustion byproducts from the heating and air conditioning can hurt air quality. But lately heating and cooling appliances have also become much more energy-efficient. More heat is captured and less is vented away, which means that the vented waste is cooler and more apt to condense. This can lead to moisture problems and mold symptoms, the spores from which often negatively affect air quality.

Other Degraders of Indoor Air Quality

Bad air quality outdoors (from air pollution, pesticides, radon, etc.) can seep inside. There may be asbestos in the paint, insulation, or ceiling tiles, or there may be pressed wood in the cabinetry, both of which have the potential to degrade air quality. Then there are volatile organic compounds (VOCs), which are chemicals found in paints or lacquers, paint strippers, varnishes or waxes, cleaning supplies, pesticides, building materials, furnishings, air fresheners or moth repellents, and dry-cleaned clothing. Introducing VOCs into the home air can not only harm its quality but cause ear, nose, or throat irritation, headaches, nausea, organ damage, and cancer.

Assessment of Air Quality

You can assess indoor air quality informally by acclimating to the outdoors and then, upon re-entering the house, noting whether or not you detect odors or staleness. Also keep an eye out for condensation on windows or walls and the development of mold.

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