Outdoor Air Pollutants Impact Indoor Air Quality

October 01, 2021


Did you know that one of the largest external factors on your indoor air quality comes from outdoor air pollutants?  It’s easy to think that just keep your doors and windows shut is enough to keep outdoor pollutants from impacting your indoor quality because, quite frankly, it makes sense.  However, there is so much more to it than that.  We will show what some of the most common outdoor air pollutants are, how it relates to your indoor air quality, and a few tips to minimize your exposure to these pollutants in your home.

Outdoor Air Pollutants

Outdoor air pollutants can take many forms, present multiple different side effects to life on earth, and impact the lives of each of us every day in many different ways.  The EPA classifies these pollutants as Criteria Pollutants and Air Toxics and Other Air Pollutants.  For our purposes here, we will be primarily focused on the Criteria Pollutants, but just so you know what they are, Air Toxics and Other Air Pollutants are the air pollutants that are known to cause cancer or other serious side effects that can be harmful to your health.  The EPA regulates these pollutants under the Clean Air Act.

There are six common pollutants in the air that fall under the category of Criteria Pollutants.  These pollutants are carbon monoxide, nitrogen dioxide, lead, ozone, particulate matter of different size fractions, and sulfur dioxide.  The EPA regulates each of these through the development of human health-based and environmentally-based criteria to set permissible levels.  These regulations are also found in the Clean Air Act.

Below is a list of where these pollutants can originate:

  • Sources of Outdoor Air Pollutants
  • Gas powered vehicles – lead, carbon monoxide, sulfur dioxide, and others
  • Power plants – arsenic, formaldehyde, acid gases, lead, and others
  • Industrial facilities – nitrogen oxide, sulfur dioxide, carbon monoxide, and others
  • Wildfires – carbon dioxide, black carbon, ozone precursors, and others
  • Factories – acid gases, carbon monoxide, smog, and others
  • Agricultural areas – carbon dioxide, nitrous oxide, and others
  • Cities – Smog and other greenhouse gas pollutants

But What Do Outdoor Air Pollutants Have to do with My Indoor Air Quality?

In short…everything.  The EPA has shown that the concentration of some pollutants can be as much as five times higher indoors than they would be outdoors.  When you consider that the average American spends more than 90% of the life indoors, you can quickly start to see how impactful these outdoor air pollutants can be to your indoor air quality.  You may be wondering how these outdoor pollutants manage to find their way inside and become so concentrated.  Here are the most common ways for outdoor pollutants to enter the home:

  • Open Windows and Doors
  • Improperly Sealed Windows
  • Chimneys/Fireplaces

So How Do I Minimize My Exposure to These Pollutants in My Home?

While eliminating all air pollutant exposure in the home is an impossible task, there are some things that you can do to minimize your exposure to these pollutants in your home and increase your indoor air quality.

  1. Keep Your Indoor Air Filter Changed Regularly.  Most indoor air filters have a life span of 90 days and should be changed 4 times per year.  Indoor air filters can reduce up to 96% of airborne pollutants, depending on the MERV rating of the filter. (You can find out more about MERV ratings HERE).  This is one of the easiest and most cost-effective ways to improve your indoor air quality and minimize outdoor pollutants in the home.
  2. Insulate Windows and Doors.  As homes are exposed to various weather elements throughout multiple season each year and they start to age, seals and weather-stripping can slowly start to deteriorate and cause cracks to form around windows and doors.  These cracks allow outdoor air to constantly seep into your home and contaminate your indoor air.  It is suggested that this process of re-sealing windows and doors should be done approximately every 5 years.  Beyond just improving your indoor air quality, this will also help keep your electricity costs down by allows your HVAC unit to function more efficiently.
  3. Monitor the Air Quality in your Area.  Location plays a major factor in which pollutants may be in your outdoor air and the concentration levels of them.  For instance, people who live in our around larger cities will typically have greater concentration of carbon monoxide while others may live in a more wet climate where the rain can wash away and dissolve some of those outdoor pollutants.  Knowing and monitoring the air quality in your area can help you prepare your home in the best way possible to keep your indoor air quality high and which outdoor pollutants you are most susceptible to.


Outdoor air pollutants impact each of our lives in many different ways.   While we may not be able to eliminate them, it doesn’t mean that we have to let our indoor air quality suffer.  After all, indoors is where most of us spend the majority of our time.  These are just a few of the ways that you can help combat outdoor air pollutants in your home.  For more on indoor air quality and air filtration, take a look at some of our other articles.

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