| 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 |
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From: 11.6.2008 EN Official Journal of the European Union L 152; information respectively from Annexes XI, XIV, VII and XIII