| Averaging period | Limit value | Margin of tolerance | Date by which limit value is to be met | |
|---|---|---|---|---|
| The maximum daily 8-hour mean concentration shall be selected by examining 8-hour running averages, calculated from hourly data and updated each hour. Each 8-hour average so calculated shall be assigned to the day on which it ends, i.e. the first calculation period for any one day shall be the period from 17:00 on the previous day to 01:00 on that day; the last calculation period for any one day shall be the period from 16:00 to 24:00 on that day. | ||||
| Limit value for the protection of human health | Maximum daily 8-hour mean | 10mg/m3 | 4 mg/m3 on 1st January 2003, reducing every 12 months thereafter by 2 mg/m3 to reach 0 mg/m3 by 1 January 2005 | 1 January 2005 |