The air quality index we use
Every index we report uses the Indian National Air Quality Index from the Central Pollution Control Board (CPCB). Band names are used exactly as CPCB defines them. The table shows the PM2.5 breakpoints, which apply to a 24-hour average.
| Band | PM2.5, 24-hour (µg/m³) | Sub-index |
|---|---|---|
| Good | 0 to 30 | 0 to 50 |
| Satisfactory | 31 to 60 | 51 to 100 |
| Moderate | 61 to 90 | 101 to 200 |
| Poor | 91 to 120 | 201 to 300 |
| Very poor | 121 to 250 | 301 to 400 |
| Severe | Above 250 | 401 to 500 |
Where we show a band for a shorter period, such as a single reading, we say so, because the official index is defined on 24-hour averages.
Reporting uncertainty
Each paper states its limitations as plainly as its findings: the instrument used, how long it ran, how much data was captured and what the measurement cannot show.
Validation
Low-cost measurements are checked against reference instruments. A co-location study comparing SentioAir monitors with reference instruments is in preparation and will be published here.
Data and code
Where we can, the data behind a paper is listed on the datasets page under an open licence, so that others can reproduce the result.