Why Is Indoor Air Pollution Worse Than Outdoor Pollution?

January 04, 2024

Did you know the air inside a building or home can be more contaminated than the outdoor air? You’d think our indoor air quality would be better than it is outside with all the windows, doors, and HVAC systems in our homes and offices to keep out airborne pollutants, but this isn't always the case.

So, why is indoor air pollution worse than outdoor?

It's an important question, especially since we spend roughly 90% of our time indoors. Understanding why our indoor air isn't as fresh as we assume can lead to steps that improve our air quality and curb the associated health risks.

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Common Types of Indoor Air Pollutants and Their Sources

If you’re wondering whether air quality is better inside or outside, consider these prevalent indoor air pollutants and their origins.

Dust and Pet Dander

These common household pollutants may include dead skin, hair, insect remains, etc. Dust mites and pet dander can significantly impact indoor air quality, posing health risks, particularly for allergy and asthma sufferers.


Mold thrives in moist and humid environments like bathrooms, basements, and under the kitchen sink. When airborne, mold spores can cause respiratory problems and allergic reactions like sneezing, coughing, and eye irritation.

Volatile Organic Compounds (VOCs)

Products like paints and cleaning agents emit these gasses. VOCs can cause health problems ranging from throat irritation to severe conditions like liver damage. VOCs such as benzene, ethylene glycol, formaldehyde, methylene chloride, and tetrachloroethylene, can be harmful, with some causing cancer.

Carbon Monoxide (CO)

This colorless, odorless gas is a lethal indoor pollutant. It enters homes through malfunctioning appliances, like heaters, stoves, and car exhausts. CO exposure can cause headaches, dizziness, and even fatal poisoning, particularly in enclosed spaces where the gas can accumulate rapidly, endangering occupants.


Like carbon monoxide, radon is a stealthy indoor air pollutant: odorless, invisible, and radioactive. It sneaks into homes through foundation cracks or wall gaps. Over time, breathing air tainted with radon in poorly ventilated spaces can significantly increase the risk of lung cancer, making it a severe and hidden danger for residents.

Secondhand Smoke

Secondhand smoke infiltrates homes from exhaled tobacco smoke and burning tobacco products. It's a hazardous indoor air pollutant containing over 7,000 chemicals, many of which are toxic and carcinogenic. This smoke poses serious health risks, especially to children and non-smoking adults, by compromising lung function and increasing the likelihood of respiratory infections, asthma, and even cancer. Because it tends to linger on fabrics and carpets, its harmful effects can persist long after the smoke has cleared.

Understanding these pollutants is critical to answering whether air quality is better inside or outside and taking steps to improve it.

Sources of Outdoor Air Pollutants

When we're talking about indoor air quality vs outdoor, we should also consider what's going on outside. Natural and human-made factors can influence outdoor air quality. For instance, cars, buses, and trucks emit hazardous gasses like nitrogen oxides, carbon monoxide, and tiny airborne particles.

Construction, farming, and industrial activities also stir up dust and chemicals. Think about the pesticides and fertilizers used in agriculture, the dust and debris from construction sites, or the VOCs from a power plant smokestack—all adding layers to outdoor air pollution.

Nature plays a role, too. Pollen from plants, dust from storms, and wildfire fumes are all significant natural contributors to outdoor air pollution.

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Importance of Improving Indoor Air Quality

Most of us spend much of our time indoors—at home, in the office, you name it. And the air in these places can teem with pollutants from daily activities like cooking, using cleaning products, or even your favorite scented candle. These activities release particles and gasses that can seriously degrade indoor air quality. And unlike the great outdoors, many indoor spaces lack sufficient ventilation to naturally get rid of these pollutants, meaning they can build up over time.

This issue extends beyond mere odor control or alleviating a sense of stuffiness. Poor indoor air quality can have real, tangible effects on our health—more than just sneezes or a bit of coughing.

Long-term exposure to polluted indoor air can lead to serious respiratory diseases, exacerbate allergies, and even affect cardiovascular health. Poor air quality may even affect your sleep, leaving you fatigued throughout the day.

However, the situation is not hopeless. The good news is that by taking proactive steps, we can significantly improve the air quality in our homes and offices, making them cleaner for all.

How to Improve Poor Indoor Air Quality

By now, it should be clear why indoor air pollution is worse than outdoor. Now, let’s discuss how to combat the problem. Here are a few practical and effective ways to improve indoor air quality and keep your HVAC system running smoothly. Here’s what you can do:

  • Boost Natural Ventilation: It's pretty straightforward—open the windows and doors when you can. This simple step is an effective way to let fresh air in and push out indoor pollutants.
  • Pick the Right Air Purifiers: A good air purifier is an excellent way to keep your indoor air fresh. It captures numerous tiny particles floating around, easing the load on your HVAC system. Just remember to change the filters regularly! We recommend changing the filters at least every 90 days. Most homes need more frequent filter changes due to indoor air pollutants. Schedule an appointment with an HVAC professional to learn the best practice for your home.
  • Control Humidity Levels: Aim to keep your indoor humidity around 30–50%. Too much moisture promotes mold and dust mites. A dehumidifier can help, as can houseplants, which naturally regulate air moisture.
  • Regular HVAC Check-ups: Keep your HVAC system in top shape with regular maintenance. Clean and replace filters often to prevent dust and pollutants from recirculating and putting strain on the system.
  • Mind the VOCs: Volatile organic compounds, commonly found in paints, aerosols, and cleaners, are not your friends when it comes to air quality. Choosing low-VOC products reduces their impact.
  • Green Cleaning Habits: Choose natural cleaning products over those loaded with chemicals. This approach enhances air quality and extends your HVAC system's lifespan by reducing the amount of harsh chemicals it has to filter out.
  • Houseplants to the Rescue: Some plants are not just for decoration; they actually clean the air! Spider plants, peace lilies, and snake plants are great for this. They absorb pollutants and give your HVAC a little break.

Improving indoor air quality can help create a healthier space for you and your loved ones. Indoor air pollution can be more harmful than what we face outdoors. Keeping these pollutants in check means your HVAC system can work more efficiently, making your home a breath of fresh air in more ways than one!

Breathe Easy with Hamilton's Indoor Air Solutions

Wondering why indoor air pollution is worse than outdoor? Let Hamilton, with 40 years of trust and experience in Kansas City, be your answer. Our experienced team offers “no surprises pricing” for all your HVAC needs. We listen, solve, and stand by our upfront estimates, ensuring quality work every time.

Contact us at (913) 227-4943 for friendly, professional service and peace of mind with Hamilton Plumbing, Heating, A/C & Rooter. Our team handles:

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Last Updated: January 04, 2024