Division A Alert thresholds for pollutants other than ozone
United Kingdom
To be measured over three consecutive hours at locations representative of air quality over at least 100 km2 or an entire zone or agglomeration, whichever is the smaller.
| Pollutant | Alert threshold |
|---|---|
| Sulphur dioxide | 500 μg/m3 |
| Nitrogen dioxide | 400 μg/m3 |