Annex XIII CRITICAL LEVELS FOR THE PROTECTION OF VEGETATION
United Kingdom
| Averaging period | Critical level | Margin of tolerance |
|---|---|---|
| Sulphur dioxide | ||
| Calendar year and winter (1 October to 31 March) | 20 μg/m3 | None |
| Oxides of nitrogen | ||
| Calendar year | 30 μg/m3 NOx | None |