Air quality index (AQI⁺) and PM2.5 air pollution in Connecticut •
When air quality in your area reaches unhealthy levels, we'll send you a quick alert, along with expert tips on how to reduce your exposure.
Real-time most polluted cities in Connecticut
Real-time cleanest cities in Connecticut
When outdoor air quality drops, the EPA recommends upgrading to a MERV 13 filter — or the highest-rated filter your HVAC system can handle — to help capture more of the fine particulate (PM2.5) that comes with poor air quality. MERV 13 is the highest rating most residential systems can run without restricting airflow.
AQI stands for Air Quality Index, the EPA's scale for reporting daily air quality. It runs from 0 to 500. The higher the number, the greater the level of air pollution. Values at or below 100 are generally considered satisfactory; values above 100 mean air quality is unhealthy, first for sensitive groups, then for everyone as numbers climb.
The AQI tracks five major pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. The reported AQI value reflects whichever pollutant is highest at that time — most often ozone or fine particles (PM2.5).
Monitoring stations measure pollutant concentrations, and the EPA converts each into a standardized 0–500 score using set breakpoints. Each pollutant gets its own sub-index, and the highest sub-index becomes the reported AQI. That's why a single number can represent different pollutants on different days.
An AQI of 0–50 is rated "Good" — air quality poses little or no risk. 51–100 is "Moderate," acceptable for most people though unusually sensitive individuals may want to limit prolonged outdoor exertion. Anything at or below 100 is generally considered satisfactory air quality.
100 is the dividing line: at or below it, air quality is satisfactory for the general public. From 101–150, air is "Unhealthy for Sensitive Groups" — people with respiratory conditions, older adults, and children. From 151–200, it's "Unhealthy" and everyone may begin to feel effects.
Short-term AQI spikes usually come from wildfire smoke, temperature inversions that trap pollutants near the ground, high-ozone weather (hot, sunny, stagnant days), or heavy traffic and industrial activity. Check a real-time source like the map on this page to see which pollutant is driving today's reading in your area.
Many runners follow the EPA category lines: below 50, no adjustment needed; 51–100, unusually sensitive people may shorten intense workouts; above 100, sensitive groups are advised to reduce prolonged or heavy outdoor exertion; above 150, that advice extends to everyone. Exercise increases how much air you breathe in, which is why thresholds matter more during workouts.
A common rule of thumb is to keep windows open when the AQI is under 100 and close them when it climbs above, especially during wildfire smoke events when fine particles are elevated. When windows are closed, running your HVAC system with a fresh filter helps capture particles circulating indoors.
Public health agencies generally suggest considering a well-fitted N95-style respirator outdoors when the AQI exceeds 150, particularly during smoke events. Cloth and surgical masks don't filter fine particles effectively. Follow guidance from your local health department, which may adjust recommendations during severe episodes.
Use the live AQI map to see outdoor air conditions in your part of Connecticut. Check your town or ZIP, note the color and number, and plan outdoor time or focus on indoor air if levels rise.
Check real-time Connecticut AQI: Visit AirNow.gov AirNow — the official EPA interactive map showing current air quality conditions across all Connecticut counties.
Current conditions: Connecticut's air quality typically ranges from Good (AQI 0-50) to Moderate (AQI 51-100). When AQI values exceed 100, air quality is considered unhealthy.
Quick AQI Scale:
0-50 (Green): Good — safe for all
51-100 (Yellow): Moderate — acceptable
101-150 (Orange): Unhealthy for sensitive groups
151+ (Red/Purple): Unhealthy to hazardous
The live AQI map gives a quick view of outdoor air for your town and helps you time outdoor plans.
Traffic, summer ozone, regional wildfire smoke, and winter stagnation are the main drivers of higher readings in Connecticut.
Close windows, use recirculation, and keep at least one room cleaner on bad air days.
Use a Filterbuy MERV 8, 11, or 13 filter that matches your system to help reduce indoor particles while outdoor levels change.
Connecticut’s air shifts with weather, season, and wind. Traffic on I-95, I-84, and other corridors adds pollution during rush hours. Hot, sunny afternoons can raise ozone. Regional wildfire smoke can drift into the state and lift fine particle levels even when the sky only looks hazy. On still winter days, pollution can linger closer to neighborhoods.
In August 2025, millions across the Northeast were under air quality alerts as smoke from Canadian wildfires drifted over the region. Forecasts covered Connecticut with hazy skies and AQI levels ranging from moderate to unhealthy, along with health guidance to limit outdoor activity when smoke was thick.
In April 2025, a report covered by the CT Post said Connecticut’s air quality has worsened in recent years, with the New Haven–Waterbury–Hartford area ranking higher for ozone and several counties recording more unhealthy days. Experts noted that much of the state’s pollution arrives on the wind from outside Connecticut, and they urged residents to watch the AQI and adjust outdoor plans on higher days.
Open the map and look up your location. Lower numbers with cooler colors mean cleaner air. Higher numbers with warmer colors mean more pollution. If the reading climbs during the day, keep outdoor time shorter or move hard activity indoors. This matters most for people with asthma, COPD, or heart disease, and for young children and older adults. Conditions can change across short distances, so compare nearby areas when you plan.
Use the map like a daily weather check. Look in the morning before errands, outdoor work, or exercise. Recheck if wind shifts, heat builds, or smoke appears in the forecast. If your route shows higher readings than your neighborhood, pick a different path or wait until conditions ease.
On higher days, small changes help. Keep workouts shorter and choose lighter activities. Pick routes away from heavy traffic and idling areas. Drink water and rest in shade or an indoor space when you can. If coughing, chest tightness, or shortness of breath starts, go indoors and rest.
Close windows during the worst hours and run AC or HVAC on recirculate instead of pulling outdoor air. Avoid indoor smoke and strong sprays. Do not smoke indoors. Skip wood fires. If you have a portable air cleaner, run it in the bedroom or main living area so at least one room stays cleaner.
Keep a spare HVAC filter on hand and know the highest MERV your system allows
Choose one “cleaner room” and be ready to run a portable air cleaner there
Learn recirculate settings on your home system and in your car
Watch wind and smoke forecasts along with the live AQI map
When air improves, do a short cleanup. Wipe hard surfaces with a damp cloth or microfiber. Vacuum rugs and carpets with a HEPA type vacuum if you have one. Wash bedding and throws. Let the HVAC fan run for a few hours with a clean filter, then check the filter and replace it if it looks loaded.
Choose MERV 8 for everyday dust and larger pollen and to help keep the system clean. Use MERV 11 if you have pets or mild allergies and want better capture of small particles like dander and many mold spores. Consider MERV 13 for finer particles in smoke and urban haze, but only if your system is rated for higher efficiency. If you are not sure, follow the HVAC maker’s guidance or ask a technician.
Filterbuy provides U.S.-made pleated filters in many standard and custom sizes so the filter fits well and reduces air bypass. The synthetic media captures more than basic fiberglass and still supports airflow when changed on time. Many homes replace filters every one to three months. Orders ship fast with free shipping in the continental United States, and Auto-Delivery helps you stay on schedule.
A live map that shows current outdoor air for your location with one number and a matching color.
Check in the morning before plans. Recheck later if wind changes, heat builds, or smoke is in the forecast.
Traffic, wind direction, terrain, and local sources like construction or industry can change conditions over short distances.
Keep workouts shorter or move them indoors. Sensitive groups should be extra careful.
Keep them closed during the worst hours and use recirculate on AC or HVAC.
A well-fitting N95 or similar respirator can reduce smoke particles. Cloth and surgical masks are not designed for smoke.
Close windows, use recirculation, avoid indoor smoke and strong sprays, and run a portable air cleaner if you have one.
Use MERV 8 for basic dust. Choose MERV 11 for homes with pets or mild allergies. Consider MERV 13 for finer particles like smoke only if your system allows it.
Many homes replace filters every one to three months. Check sooner during long heating or cooling periods or during smoke events.
Stop, go indoors, rest, and follow your care plan. Seek medical advice if symptoms persist or worsen.
