Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe (c. 50)

ANNEX VII OZONE TARGET VALUES AND LONG-TERM OBJECTIVES

B. Target values

a Compliance with target values will be assessed as of this date. That is, 2010 will be the first year the data for which is used in calculating compliance over the following three or five years, as appropriate.
b The maximum daily eight-hour mean concentration shall be selected by examining eight-hour running averages, calculated from hourly data and updated each hour. Each eight -hour average so calculated shall be assigned to the day on which it ends. i.e. the first calculation period for any one day will be the period from 17:00 on the previous day to 01:00 on that day; the last calculation period for any one day will be the period from 16:00 to 24:00 on the day.
c If the three or five year averages cannot be determined on the basis of a full and consecutive set of annual data, the minimum annual data required for checking compliance with the target values will be as follows: for the target value for the protection of human health: valid data for one year, for the target value for the protection of vegetation: valid data for three years.
Objective	Averaging period	Target value	Date by which target value should be meta
Protection of human health	Maximum daily eight-hour meanb	120 µg/m3 not to be exceeded on more than 25 days per calendar year averaged over three yearsc	1.1.2010
Protection of vegetation	May to July	AOT40 (calculated from 1 h values) 18 000 µg/m3 · h averaged over five yearsc	1.1.2010