The Air Quality Standards Regulations 2007

3.  In this Part—

(a) all values shall be expressed in μg/m³;

(b) the volume shall be standardised at the following conditions of temperature and pressure: 293K and 101.3kPa;

(c) the time shall be specified in Central European Time;

(d) “AOT40” (expressed in (μg/m³) hours) means the sum of the difference between hourly concentrations greater than 80 μg/m³ (which equals 40 parts per billion) and 80 μg/m³ over a given period using only the 1 hour values measured between 8:00 and 20:00 Central European Time each day; and

(e) in order to be valid, the annual data on exceedances used to check compliance with the target values and long-term objectives below shall meet the criteria set out in Part 2 of Schedule 12.

Target values

The attainment date for the target values set out in the following table is 2010, with compliance assessed over the periods indicated for each target value in the table.

Column header	Parameter	Target value and assessment(1)
(1) Compliance with target values will be assessed as of this value. That is, 2010 will be the first year the data for which is used in calculating compliance over three or five years, as appropriate.
(2) 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, that is, 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 will be the period from 16:00 to 24:00 on the day.
(3) 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 shall be as follows: (i) for the target value for the protection of human health, valid data for one year; and (ii) for the target value for the protection of vegetation, valid data for three years.
Target value for the protection of human health	Maximum daily 8 hour mean(2)	120 μg/m³ not to be exceeded on more than 25 days per calendar year averaged over three years(3)
Target value for the protection of vegetation	AOT 40, calculated from 1 hour values from May to July	18,000 μg/m³.h averaged over five years(3)

Long-term objectives

	Parameter	Long-term objective
Long-term objective for the protection of human health	Maximum daily 8 hour mean within a calendar year	120 μg/m³
Long-term objective for the protection of vegetation	AOT40, calculated from 1 hour values from May to July	6,000 μg/m³.h