---
title: "The Air Quality Index (AQI): categories and colors"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source: https://www.airnow.gov/aqi/aqi-basics/
source_license: "public domain (US government work)"
attribution: "Summary by iinventedlight (AI-assisted). Source: AirNow (US EPA and partners), \"AQI Basics\" (public domain (US government work))."
condensed_by: "iinventedlight (Grok Bot, AI-assisted)"
fact_checked: 2026-11-02
date: 2026-11-02
status: reviewed
reviewed_on: 2026-11-02
category: science
checked_on: 2026-11-02
license_url: https://creativecommons.org/licenses/by/4.0/
source: https://www.airnow.gov/aqi/aqi-basics/
source_license: "public domain (US government work)"
attribution: "Summary by iinventedlight (AI-assisted), condensed and paraphrased; sources: AirNow (US EPA and partners), \"AQI Basics\" (public domain, US government work)"
condensed_by: "iinventedlight (Grok Bot, AI-assisted)"
fact_checked: 2026-11-02
date: 2026-11-02
category: science
tags: science, air-quality, aqi, wildfire-smoke, epa
checked_on: 2026-11-02
sources:
  - id: S1
    title: "AQI Basics"
    publisher: "AirNow (US EPA and partners)"
    url: https://www.airnow.gov/aqi/aqi-basics/
    accessed: 2026-11-02
    license: "public domain (US government work)"
    attribution: "AirNow (US EPA and partners), \"AQI Basics\" (public domain, US government work)"
---
# The Air Quality Index (AQI): categories and colors

# The Air Quality Index (AQI): categories and colors

## Summary
The US AQI is the EPA's index for reporting outdoor air quality. It runs from 0 to over 300 in six color-coded categories, from Good (green, 0-50) to Hazardous (maroon, 301 and up). Values above 100 are unhealthy, first for sensitive groups and then for everyone. During wildfires, AirNow's Fire and Smoke Map shows smoke impacts.

*Draft. License: CC BY 4.0 (this summary). Sources: [S1] AirNow (US EPA and partners), "AQI Basics" (public domain (US government work)).*

## Facts
- id: F1
  claim: The US AQI is EPA's tool for communicating outdoor air quality and health; higher values mean more pollution and greater health concern.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F2
  claim: Green, Good, 0-50: air quality is satisfactory with little or no risk.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F3
  claim: Yellow, Moderate, 51-100: acceptable, though some unusually sensitive people may be at risk.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F4
  claim: Orange, Unhealthy for Sensitive Groups, 101-150: sensitive groups may have health effects; the general public is less likely to be affected.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F5
  claim: Red, Unhealthy, 151-200: some of the general public may have effects, and sensitive groups more serious effects.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F6
  claim: Purple, Very Unhealthy, 201-300: a health alert with increased risk for everyone.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F7
  claim: Maroon, Hazardous, 301 and higher: a health warning of emergency conditions.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02
- id: F8
  claim: For each pollutant, an AQI of 100 generally matches the short-term national air quality standard for protecting public health.
  confidence: medium
  date: 2026-11-02
  sources: [S1]
  license: CC BY 4.0
  checked_on: 2026-11-02

## Caveats
- The AQI is calculated per pollutant (e.g. ozone, particle pollution); the reported value is for the worst one.
- Other countries use different indices; numbers are not directly comparable.

## Pointers
- id: P1
  answers: Current AQI and wildfire smoke map
  where: https://fire.airnow.gov/
  access: free, public web page