Data: EPA AirNow, FEMA National Risk Index Last verified: 2026-05-03

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. Boulder's average AQI of 65 falls in the "Moderate" range.

How do wildfires affect air quality?

Wildfire smoke contains fine particulate matter (PM2.5) that can travel hundreds of miles and dramatically spike AQI readings. During fire season, even cities far from active fires can experience unhealthy air. HEPA air purifiers (rated for PM2.5) are the most effective indoor protection. Check AirNow.gov for real-time conditions during fire season.

Air Quality Map: Boulder, CO

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 Boulder

AQI varies across Boulder's 16 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
80301	68	Moderate	34	34	View report →
80302	68	Moderate	33	41	View report →
80303	68	Moderate	34	43	View report →
80304	68	Moderate	33	41	View report →
80305	68	Moderate	33	38	View report →
80309	68	Moderate	33	11	View report →
80310	68	Moderate	33	11	View report →
80321	68	Moderate	33	11	View report →
80322	68	Moderate	33	11	View report →
80323	68	Moderate	33	11	View report →
80328	68	Moderate	33	11	View report →
80329	68	Moderate	33	11	View report →
80306	57	Moderate	33	16	View report →
80307	57	Moderate	33	11	View report →
80308	57	Moderate	33	16	View report →

Showing 15 of 16 ZIP codes. View all.

Air Quality Overview

Boulder, Colorado has moderate air quality with an average AQI of 65. 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 Boulder

AQI varies across Boulder's 16 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

Showing 15 of 16 ZIP codes. Check your specific ZIP for detailed data.

Wildfire Smoke Risk

Boulder has an elevated wildfire smoke risk with an average smoke risk score of 33 (scale 0-100). There have been 382 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	33
Max smoke risk score	34
Fires within 100 km	382
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

Boulder has an average mold risk score of 21 out of 100.

Factor	Value
Mold risk score	21/100
Average humidity	44% RH
High-risk ZIPs	0
Peak season	balanced

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 65), 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

Boulder vs. Nearby Colorado Cities

How Boulder's air quality compares to nearby cities:

ZIP Codes in Boulder

Boulder covers 16 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.