WeatherWidget Air Index
Comprehensive guide to Air Pollution Index (AQI) levels, chemical pollutant concentrations, international standards, and health recommendations provided by OpenWeather for WeatherWidget.
Introduction & Data Provider
WeatherWidget now delivers comprehensive environmental and air pollution intelligence alongside core meteorological data. Air quality data is sourced directly from OpenWeather's Air Pollution API. The service computes real-time, forecasted (up to 4 days with hourly granularity), and historical air pollution levels for any geographical coordinate across the globe.
Data Provider
Global API Granularity
Tracked Gaseous Pollutants
Tracked Particulates
Monitored Pollutants & Chemical Compounds
The API returns individual concentration readings for six primary index-determining pollutants plus two auxiliary compounds. Concentrations are measured in micrograms per cubic metre (μg/m³) or parts per million (ppm) / parts per billion (ppb).
Microscopic airborne particles 2.5 micrometres or smaller. Able to penetrate deeply into the pulmonary alveoli and enter the bloodstream, triggering severe cardiovascular and respiratory complications.
Inhalable particles up to 10 micrometres in diameter. Causes irritation of the upper respiratory tract, eyes, and throat, exacerbating chronic conditions like asthma and bronchitis.
A reddish-brown pungent toxic gas formed through high-temperature combustion. Directly causes airway inflammation, reduces lung immunity, and serves as a critical precursor to ground-level ozone and secondary particulates.
A colorless gas with a choking odor. Rapidly causes bronchoconstriction and respiratory distress, especially in asthmatic individuals. A major contributor to acid rain and environmental acidification.
A secondary atmospheric pollutant created through photochemical reactions between NOx and Volatile Organic Compounds (VOCs) under strong sunlight. Causes intense lung irritation, coughing, and chest tightness.
An odorless, colorless gas resulting from incomplete fuel combustion. Binds preferentially to hemoglobin in blood to form carboxyhemoglobin, inhibiting oxygen delivery to vital organs and tissue.
An alkaline gaseous compound with a pungent odor. Acts as a key catalyst in atmospheric chemistry by combining with nitric and sulphuric acids to form fine secondary ammonium particles.
A free radical gas produced during high-temperature fuel burning. Readily oxidises in ambient air into nitrogen dioxide (NO&sub2;) and contributes to atmospheric ozone dynamics.
OpenWeather Global Air Quality Index (AQI 1–5)
This is OpenWeather's primary index scale, returned directly by the API in the main.aqi field. The index maps integer scores from 1 (Good) to 5 (Very Poor) based on pollutant concentrations (μg/m³).
| Qualitative Status | Index (AQI) | SO&sub2; (μg/m³) | NO&sub2; (μg/m³) | PM&sub1;&sub0; (μg/m³) | PM&sub2;.&sub5; (μg/m³) | O&sub3; (μg/m³) | CO (μg/m³) |
|---|---|---|---|---|---|---|---|
| Good | 1 | [0; 20) | [0; 40) | [0; 20) | [0; 10) | [0; 60) | [0; 4400) |
| Fair | 2 | [20; 80) | [40; 70) | [20; 50) | [10; 25) | [60; 100) | [4400; 9400) |
| Moderate | 3 | [80; 250) | [70; 150) | [50; 100) | [25; 50) | [100; 140) | [9400; 12400) |
| Poor | 4 | [250; 350) | [150; 200) | [100; 200) | [50; 75) | [140; 180) | [12400; 15400) |
| Very Poor | 5 | ≥ 350 | ≥ 200 | ≥ 200 | ≥ 75 | ≥ 180 | ≥ 15400 |
nh3 (Ammonia: nominal range 0.1 – 200 μg/m³) and no (Nitrogen monoxide: nominal range 0.1 – 100 μg/m³). While available for scientific inquiry and air chemistry modeling, they do not directly modify the composite 1–5 AQI score.
United Kingdom Air Quality Index Scale (DAQI)
The UK Department for Environment, Food & Rural Affairs (DEFRA) operates the Daily Air Quality Index (DAQI). The index uses a 10-point scale grouped into 4 qualitative bands to communicate air pollution health risks to the public.
| Band | Index Level | SO&sub2; (μg/m³) | NO&sub2; (μg/m³) | PM&sub2;.&sub5; (μg/m³) | PM&sub1;&sub0; (μg/m³) | O&sub3; (μg/m³) |
|---|---|---|---|---|---|---|
| Low | 1 | 0 – 88 | 0 – 67 | 0 – 11 | 0 – 16 | 0 – 33 |
| Low | 2 | 89 – 177 | 68 – 134 | 12 – 23 | 17 – 33 | 34 – 66 |
| Low | 3 | 178 – 266 | 135 – 200 | 24 – 35 | 34 – 50 | 67 – 100 |
| Moderate | 4 | 267 – 354 | 201 – 267 | 36 – 41 | 52 – 58 | 101 – 120 |
| Moderate | 5 | 355 – 443 | 268 – 334 | 42 – 47 | 59 – 66 | 121 – 140 |
| Moderate | 6 | 444 – 532 | 335 – 400 | 48 – 53 | 67 – 75 | 141 – 160 |
| High | 7 | 533 – 710 | 401 – 467 | 54 – 58 | 76 – 83 | 161 – 187 |
| High | 8 | 711 – 887 | 468 – 534 | 59 – 64 | 84 – 91 | 188 – 213 |
| High | 9 | 888 – 1064 | 535 – 600 | 65 – 70 | 92 – 100 | 214 – 240 |
| Very High | 10 | ≥ 1065 | ≥ 601 | ≥ 71 | ≥ 101 | ≥ 241 |
European Air Quality Index Scale (CAQI)
Used across the European Union and monitored by the European Environment Agency (EEA). The Common Air Quality Index (CAQI) evaluates hourly and daily pollution concentrations to present comparable air quality figures across European metropolitan areas.
| Qualitative Name | Index / Sub-index | NO&sub2; (μg/m³) | PM&sub1;&sub0; (μg/m³) | O&sub3; (μg/m³) | PM&sub2;.&sub5; (μg/m³) |
|---|---|---|---|---|---|
| Very Low | 0 – 25 | 0 – 50 | 0 – 25 | 0 – 60 | 0 – 15 |
| Low | 25 – 50 | 50 – 100 | 25 – 50 | 60 – 120 | 15 – 30 |
| Medium | 50 – 75 | 100 – 200 | 50 – 90 | 120 – 180 | 30 – 55 |
| High | 75 – 100 | 200 – 400 | 90 – 180 | 180 – 240 | 55 – 110 |
| Very High | > 100 | > 400 | > 180 | > 240 | > 110 |
USA Air Quality Index Scale (US EPA)
The United States Environmental Protection Agency (US EPA) standard calculates an AQI running from 0 to 500+ across six health concern categories. Air quality values exceeding 300 represent emergency conditions.
| AQI Range | Level of Health Concern | Color Code | Health Description |
|---|---|---|---|
| 0 to 50 | Good | Green | Air quality is satisfactory, and air pollution poses little or no risk. |
| 51 to 100 | Moderate | Yellow | Air quality is acceptable; however, a small number of people unusually sensitive to air pollution may suffer minor irritation. |
| 101 to 150 | Unhealthy for Sensitive Groups | Orange | Members of sensitive groups (children, elderly, asthmatics) may experience health effects. The general public is not likely to be affected. |
| 151 to 200 | Unhealthy | Red | Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects. |
| 201 to 300 | Very Unhealthy | Purple | Health alert: The risk of health effects is increased for everyone in the population. |
| 301 to 500 | Hazardous | Maroon | Health warning of emergency conditions: Everyone is more likely to be seriously affected. |
| 501 to 1000 | Very Hazardous | Brown | Catastrophic emergency: Extreme health risks for the entire population. |
To translate raw ambient pollutant concentrations into the standardized US AQI scale, the EPA uses piecewise linear interpolation between defined breakpoint concentrations:
| I_low – I_high | O&sub3; (ppb 8-hr) | O&sub3; (ppb 1-hr) | PM&sub2;.&sub5; (μg/m³ 24-hr) | PM&sub1;&sub0; (μg/m³ 24-hr) | CO (ppm 8-hr) | SO&sub2; (ppb) | NO&sub2; (ppb 1-hr) |
|---|---|---|---|---|---|---|---|
| 0 – 50 | 0 – 54 | — | 0.0 – 12.0 | 0 – 54 | 0.0 – 4.4 | 0 – 35 (1-hr) | 0 – 53 |
| 51 – 100 | 55 – 70 | — | 12.1 – 35.4 | 55 – 154 | 4.5 – 9.4 | 36 – 75 (1-hr) | 54 – 100 |
| 101 – 150 | 71 – 85 | 125 – 164 | 35.5 – 55.4 | 155 – 254 | 9.5 – 12.4 | 76 – 185 (1-hr) | 101 – 360 |
| 151 – 200 | 86 – 105 | 165 – 204 | 55.5 – 150.4 | 255 – 354 | 12.5 – 15.4 | 186 – 304 (1-hr) | 361 – 649 |
| 201 – 300 | 106 – 200 | 205 – 404 | 150.5 – 250.4 | 355 – 424 | 15.5 – 30.4 | 305 – 604 (24-hr) | 650 – 1249 |
| 301 – 400 | — | 405 – 504 | 250.5 – 350.4 | 425 – 504 | 30.5 – 40.4 | 605 – 804 (24-hr) | 1250 – 1649 |
| 401 – 500 | — | 505 – 604 | 350.5 – 500.4 | 505 – 604 | 40.5 – 50.4 | 805 – 1004 (24-hr) | 1650 – 2049 |
Mainland China Air Quality Index Scale (HJ 633-2012)
Administered by China's Ministry of Ecology and Environment (MEP) under technical guideline HJ 633-2012. The system evaluates an Individual Air Quality Index (IAQI) for each pollutant, with the overall AQI determined by the highest individual IAQI value.
| AQI Range | Air Pollution Level | Air Pollution Category | General Health Assessment |
|---|---|---|---|
| 0 – 50 | Level 1 | Excellent | No air pollution risk; outdoor physical activity is unrestricted. |
| 51 – 100 | Level 2 | Good | Air quality is acceptable; very sensitive people should limit heavy exertion. |
| 101 – 150 | Level 3 | Lightly Polluted | Mild irritation possible in vulnerable groups; reduce intense outdoor sports. |
| 151 – 200 | Level 4 | Moderately Polluted | Healthy population shows slight symptoms; vulnerable groups experience aggravated distress. |
| 201 – 300 | Level 5 | Heavily Polluted | Noticeably reduced endurance in healthy population; stay indoors. |
| > 300 | Level 6 | Severely Polluted | Severe hazard; general population should avoid outdoor physical exertion. |
Concentrations are specified in μg/m³ (except Carbon Monoxide CO, which is measured in mg/m³):
| IAQI | SO&sub2; (24h) | SO&sub2; (1h)¹ | NO&sub2; (24h) | NO&sub2; (1h)¹ | PM&sub1;&sub0; (24h) | CO (24h)* | CO (1h)*¹ | O&sub3; (1h) | O&sub3; (8h) | PM&sub2;.&sub5; (24h) |
|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 50 | 50 | 150 | 40 | 100 | 50 | 2 | 5 | 160 | 100 | 35 |
| 100 | 150 | 500 | 80 | 200 | 150 | 4 | 10 | 200 | 160 | 75 |
| 150 | 475 | 650 | 180 | 700 | 250 | 14 | 35 | 300 | 215 | 115 |
| 200 | 800 | 800 | 280 | 1200 | 350 | 24 | 60 | 400 | 265 | 150 |
| 300 | 1600 | (2) | 565 | 2340 | 420 | 36 | 90 | 800 | 800 | 250 |
| 400 | 2100 | (2) | 750 | 3090 | 500 | 48 | 120 | 1000 | (3) | 350 |
| 500 | 2620 | (2) | 940 | 3840 | 600 | 60 | 150 | 1200 | (3) | 500 |
* CO units are in mg/m³. All other pollutant columns are in μg/m³.
(1) SO&sub2;, NO&sub2;, and CO 1-hour average concentrations are applied strictly for real-time reporting. For 24-hour daily reporting, the 24-hour average concentration is mandated.
(2) If the SO&sub2; concentration exceeds 800 μg/m³, use the index calculated from the 24-hour concentration instead.
(3) If the O&sub3; 8-hour concentration exceeds 800 μg/m³, use the index derived from the 1-hour concentration instead.
Health Implications & Protective Recommendations
Understanding ambient pollution levels allows you to plan outdoor physical activities, commute times, and indoor ventilation safely. Here is actionable guidance tailored to general populations and sensitive individuals:
Air quality is ideal for all normal activities. Perfect conditions for outdoor exercise, cycling, running, and natural building ventilation.
Slight risk for highly sensitive individuals with chronic asthma or COPD. Mild throat tickle or eye irritation may occur after hours of strenuous outdoor exertion.
Elevated health risks for the general population. Children, seniors, and individuals with cardiovascular disease should avoid prolonged outdoor exposure.
WeatherWidget Setup & Configuration
WeatherWidget provides seamless toggles to display real-time air quality index scores and individual chemical pollutant concentrations directly inside your desktop overlay.
{
"display": {
"show_air_pollution": true,
"show_aqi_badge": true,
"show_fine_particles": true,
"preferred_aqi_standard": "openweather", // "openweather" | "uk_daqi" | "europe_caqi" | "us_epa" | "china_mep"
"temperature_unit": "C"
},
"provider": {
"name": "openweathermap",
"api_key": "YOUR_OPENWEATHERMAP_API_KEY",
"refresh_interval_minutes": 30
}
}
For full instructions on configuring cities, monitors, transparency, hotkeys, and automated startup, refer to the complete WeatherWidget User Manual.