What Is the Air Quality in Knox, Indiana?

Knox, Indiana earns a C — air quality is fair, but not great. With a 5-year median AQI of 36, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.

Knox, Indiana's 5-year median AQI of 36 is 5 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Indiana, Knox, Indiana runs cleaner than the state average of 41 — a positive signal that local conditions (terrain, wind patterns, emission sources) are working in residents' favor.

For context within Indiana: Floyd, Indiana currently holds the state's cleanest grade (A, AQI 36), while Marion, Indiana sits at the bottom (C, AQI 57).

Air quality in Knox, Indiana has been getting worse over the past decade, with median AQI climbing by roughly 0.3 points per year. That bucks the national trend of broad improvement, and most often reflects either growing wildfire smoke exposure (particularly across the West) or rising local emissions from population and freight growth.

In 2014, Knox, Indiana posted a median AQI of 34. By 2023 that figure was 39 — a rise of 5 AQI points dirtier across 10 years of EPA records.

Across the past five years, this area has logged just 11 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 2 days per year, or roughly one every other month. That is a low count by national standards.

Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. Because ozone peaks in the afternoon on hot sunny days, plan outdoor exercise for early morning or after sunset on bad-air days.