Methodology, data sources, and update policy
This site is designed to help people interpret AQI and make air-quality decisions. The estimate is intentionally simple enough to be understandable, while still tied to recognizable public methodology.
1. AQI to PM2.5
The calculator first converts AQI into an estimated PM2.5 concentration using EPA-style AQI breakpoint logic. AQI is easier to look up, while PM2.5 is the dose unit needed for the cigarette-equivalent framing.
Primary reference: AirNow AQI calculator and AQI breakpoint methodology.
2. PM2.5 to cigarette-equivalent exposure
After estimating PM2.5, the site uses the Berkeley Earth cigarette-equivalence framing to make the exposure easier to understand. In plain terms, it estimates how much PM2.5 exposure corresponds to the particulate dose from cigarettes over time.
Primary reference: Berkeley Earth's air pollution and cigarette equivalence framing.
3. Direct PM2.5 mode
The calculator also accepts PM2.5 directly. In that mode, cigarette-equivalent exposure is calculated from the raw PM2.5 concentration, while AQI is derived only for category labels and scenario guidance.
This keeps PM2.5-mode results exact for users coming from particle monitors or apps that report µg/m³ directly.
4. What the estimate is good for
5. Live city data layer
City pages use EPA AirNow as a live enhancement layer where regional coverage and an API response are available. If the API is unavailable, rate-limited, unsupported for the city, or not configured in the deployment environment, the site falls back to a static planning baseline instead of failing open.
The live layer is designed as a lightweight utility feature, not a hard dependency.
6. Important limitations
- The estimate is not a medical diagnosis and does not predict an individual health outcome.
- AQI varies by pollutant and local conditions. This tool is most aligned with PM2.5-oriented exposure interpretation.
- Real-world exposure changes with exertion, indoor leakage, masks, ventilation, and time spent in cleaner or dirtier microenvironments.
7. Update policy
We review the site when the calculator logic changes, when key methodology references materially change, or when new internal content is added. Supporting pages are updated to improve clarity, internal linking, and user decision value.
The city and scenario pages remain planning aids first. The live AQI layer is intended to improve utility, but users should still interpret rapidly changing smoke or pollution events conservatively and cross-check with local authorities when needed.