When people hear “air pollution,” they usually think about traffic, factories, or summer smog. But the truth is, outdoor air pollution doesn’t stay outside – it gets into our homes. And once it’s in, it can quietly affect your family’s health, especially if someone in your home has allergies, asthma, or other breathing problems.
In Louisville, there are several key pollutants that show up again and again in local air quality reports. These include ozone, particulate matter, and harmful gases like nitrogen oxides and carbon monoxide. Some come from outside sources, like car exhaust. Others can be found inside your home in everyday products or heating systems. Understanding these pollutants is the first step in protecting your indoor air.
Ground-Level Ozone (O₃)
Ozone forms when pollution from cars and factories reacts with sunlight, something we get plenty of in Louisville during the summer. While ozone high in the atmosphere protects us, ground-level ozone can irritate your lungs and make it harder to breathe. People with asthma or other respiratory conditions are especially sensitive. It’s most common on warm, sunny days, when air tends to sit still and trap pollutants close to the ground.
Particulate Matter (PM10 and PM2.5)
Particulate matter is made up of tiny particles floating in the air, so small you can’t see them. Some come from dust, construction work, or smoke. The smallest particles (PM2.5) can travel deep into your lungs and even reach your bloodstream. These have been linked to everything from coughing and wheezing to serious heart and lung problems. Louisville tends to see higher levels in the summer and during temperature inversions in colder months.
Nitrogen Oxides (NOx)
These gases are produced when fuels are burned, especially in car engines and industrial boilers. In addition to forming ozone, NOx can directly irritate your lungs. Long-term exposure is linked to respiratory diseases and worsening asthma. Because Louisville is a regional hub with a fair amount of industry and heavy traffic, NOx is a year-round concern here.
Volatile Organic Compounds (VOCs)
VOCs are chemicals that easily evaporate into the air. You’ll find them in paint, furniture, air fresheners, and cleaning products. When they build up inside your home, they can lead to headaches, eye and throat irritation, and long-term breathing problems. They also contribute to ozone formation when they mix with NOx in sunlight.
Common sources include:
- Cleaning supplies
- New flooring or furniture
- Paints and varnishes
Carbon Monoxide (CO)
Carbon monoxide is a colorless, odorless gas that’s especially dangerous because you won’t know it’s there unless you’re monitoring for it. It forms when fuel-burning appliances like stoves or furnaces don’t work properly or aren’t vented correctly. Mild exposure can make you feel tired or dizzy. In higher doses, it can be deadly. Every home should have carbon monoxide detectors near bedrooms and major appliances.
Sulfur Dioxide (SO₂)
SO₂ comes from burning coal, oil or other fossil fuels. Although it’s more common near industrial plants, older heating systems can also release small amounts. It can make breathing uncomfortable and trigger asthma symptoms. When SO₂ combines with other particles in the air, it can also contribute to fine particulate matter.
Lead (Pb)
Lead in the air isn’t as common today as it once was, but older homes in Louisville may still contain lead-based paint. As paint chips, it can turn into dust and enter the air, especially if it’s disturbed during renovations or HVAC work. Even low levels of lead can affect children’s brain development and behavior.
How Louisville Monitors Air Pollution
Louisville’s air is tracked daily by the Metro Air Pollution Control District (APCD). They collect data from six stations across the city to determine the local Air Quality Index (AQI). This index helps residents understand when air quality is safe—and when to limit outdoor activity, especially for sensitive groups.
You can check today’s air quality levels here:
Louisville APCD – Air Quality Services
What You Can Do to Improve Your Indoor Air
While we can’t control outdoor pollution, there’s a lot you can do to protect the air inside your home. Sealing up air leaks, avoiding strong chemical cleaners, and keeping your HVAC system well-maintained can all make a big difference.
Three easy first steps:
- Use HEPA filters to trap dust and allergens
- Ventilate your home when using products with strong odors
- Schedule an indoor air quality test if you’re experiencing allergy-like symptoms, musty smells, or poor airflow
At John Waters Heating & Cooling, we offer professional indoor air testing in Louisville. If you’re concerned about your home’s air, or just want to feel more confident in your space, we’re here to help.
Call us today to schedule your air quality check.
TL;DR: Common Air Pollutants in Louisville
| Pollutant | Where It Comes From | Why It Matters |
| Ozone (O₃) | Sunlight + vehicle/industrial emissions | Irritates lungs, worsens asthma |
| PM10 / PM2.5 | Dust, smoke, construction, exhaust | Can enter lungs, trigger breathing & heart issues |
| NOx | Cars, boilers, industrial combustion | Leads to ozone, airway inflammation |
| VOCs | Paint, cleaners, furniture | Causes irritation, helps form ozone indoors |
| Carbon Monoxide | Gas appliances, furnaces | Silent, toxic gas—can cause dizziness or death |
| Sulfur Dioxide | Burning fossil fuels | Triggers asthma, contributes to particulate matter |
| Lead | Old paint, dust in older homes | Impairs child development, serious long-term effects |
