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. Onyx's average AQI of 22 falls in the "Good" 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 by ZIP Code in Onyx

AQI varies across Onyx's 1 ZIP codes based on proximity to pollution sources and local geography.

ZIP Code	AQI	Category	Wildfire	Mold
93255	22	Good	57	29	View report →

Air Quality Overview

Onyx, California has good air quality with an average AQI of 22. This means air pollution poses little or no risk. The dominant pollutant measured is PM10.

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: PM10

PM10 is one of six criteria pollutants monitored by the EPA under the Clean Air Act. Elevated levels can cause respiratory irritation and may aggravate existing health conditions.

Air Quality by ZIP Code in Onyx

AQI varies across Onyx's 1 ZIP codes based on proximity to pollution sources, traffic patterns, and local geography:

Wildfire Smoke Risk

Onyx has an elevated wildfire smoke risk with an average smoke risk score of 57 (scale 0-100). There have been 25 fires recorded within 100 km of city ZIP codes.

Metric	Value
Avg. smoke risk score	57
Max smoke risk score	57
Fires within 100 km	25
High-risk ZIP codes	1

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

Onyx has an average mold risk score of 29 out of 100.

Factor	Value
Mold risk score	29/100
Average humidity	57% RH
High-risk ZIPs	0
Peak season	winter 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 good air quality (AQI 22), Onyx residents can enjoy outdoor activities without significant restrictions. General tips:

• Monitor AQI during wildfire season for temporary spikes
• Use HEPA air purifiers indoors if you have respiratory conditions
• Maintain indoor humidity between 30-50% to prevent mold

Onyx vs. Nearby California Cities

How Onyx's air quality compares to nearby cities:

ZIP Codes in Onyx

Onyx covers 1 ZIP code. 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.