Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-07-18

What is AQI?

The Air Quality Index (AQI) is a standardized scale from 0 to 500 that measures air pollution levels. 0-50 is "Good," 51-100 is "Moderate," 101-150 is "Unhealthy for Sensitive Groups," and above 150 is "Unhealthy" for everyone. AQI tracks five major pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Norwalk's average AQI of 77 falls in the "Moderate" range.

Air Quality Map: Norwalk, CT

Each dot represents a ZIP code. Color indicates AQI level. Tap a dot for details.

Good (0-50) Moderate (51-100) USG (101-150) Unhealthy (151+)

Air Quality by ZIP Code in Norwalk

AQI varies across Norwalk's 11 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
06850	81	Moderate	11	58	View report →
06851	81	Moderate	11	58	View report →
06853	81	Moderate	11	66	View report →
06854	81	Moderate	11	63	View report →
06855	81	Moderate	11	64	View report →
06856	81	Moderate	11	42	View report →
06858	81	Moderate	11	47	View report →
06859	81	Moderate	11	47	View report →
06852	65	Moderate	11	42	View report →
06857	65	Moderate	11	47	View report →
06860	65	Moderate	11	47	View report →

Air Quality Overview

Norwalk, Connecticut has moderate air quality with an average AQI of 77. Air quality is acceptable, though some pollutants may be a concern for a small number of people who are unusually sensitive to air pollution. The dominant pollutant is Ozone.

The Air Quality Index (AQI) is an EPA-standardized scale from 0 to 500. Values below 50 are "Good," 51-100 "Moderate," 101-150 "Unhealthy for Sensitive Groups," 151-200 "Unhealthy," 201-300 "Very Unhealthy," and above 300 "Hazardous."

Dominant Pollutant: Ozone

Ground-level ozone forms when pollutants from cars, power plants, and industrial facilities react with sunlight. Unlike stratospheric ozone, ground-level ozone is harmful to breathe.

Health effects of ozone exposure:

• Irritation of the respiratory system
• Reduced lung function
• Aggravation of asthma and chronic lung diseases
• Increased susceptibility to respiratory infections

Peak times: Ozone levels are typically highest on hot, sunny afternoons. Exercise outdoors in the morning when levels are lower.

Air Quality by ZIP Code in Norwalk

AQI varies across Norwalk's 11 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

Wildfire Smoke Risk

Norwalk has an elevated wildfire smoke risk with an average smoke risk score of 11 (scale 0-100). There have been 33 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	11
Max smoke risk score	11
Fires within 100 km	33
High-risk ZIP codes	0

Wildfire smoke contains PM2.5, carbon monoxide, and volatile organic compounds. Even short-term exposure can trigger asthma attacks and respiratory distress.

Indoor Mold Risk

Norwalk has an average mold risk score of 53 out of 100, with 5 ZIP codes in the high-risk category.

Factor	Value
Mold risk score	53/100
Average humidity	68% RH
High-risk ZIPs	5
Peak season	summer high

Mold risk is influenced by humidity levels, housing age (older homes have more moisture issues), flood history, and water infrastructure quality. Indoor humidity above 60% creates favorable conditions for mold growth.

Signs of mold problems: musty odors, visible growth on walls or ceilings, worsening allergies indoors, condensation on windows. Professional mold testing ($300-$600) can identify hidden issues.

Health Recommendations

With moderate air quality (AQI 77), most people can be active outdoors. Sensitive groups should take precautions:

• Sensitive groups (asthma, COPD, heart disease): consider reducing prolonged outdoor exertion
• Keep windows closed on high-pollution days
• Use a HEPA air purifier in main living areas
• Check AirNow.gov before outdoor exercise

Norwalk vs. Nearby Connecticut Cities

How Norwalk's air quality compares to nearby cities:

ZIP Codes in Norwalk

Norwalk covers 11 ZIP codes. Air quality can vary by neighborhood based on proximity to highways, industrial areas, and green spaces. Check your specific ZIP code for localized data.

Data Sources

• Air quality: EPA AirNow - real-time and historical AQI data
• Wildfire risk: FEMA National Risk Index
• Mold risk: Derived from EPA, FEMA, Census ACS (humidity, housing age, flood history)
• Monthly AQI: EPA Air Quality Statistics

Updated daily.