Regulations 2(2), 3 and 4
| Column 1 | Column 2 | Column 3 | |
|---|---|---|---|
| Substance | Air Quality Objectives | Prescribed Date | |
| 1 | Benzene | 16.25 micrograms per cubic metre or less, when expressed as running annual mean | 31st December 2003 |
| 2 | 1,3-Butadiene | 2.25 micrograms per cubic metre or less, when expressed as a running annual mean | 31st December 2003 |
| 3 | Carbon monoxide | 11.6 milligrams per cubic metre or less, when expressed as a running 8 hour mean | 31st December 2003 |
| 4 | Lead | 0.5 micrograms per cubic metre or less, when expressed as an annual mean | 31st December 2004 |
| 5 | Lead | 0.25 micrograms per cubic metre or less, when expressed as an annual mean | 31st December 2008 |
| 6 | Nitrogen dioxide | 200 micrograms per cubic metre, when expressed as an hourly mean, not to be exceeded more than 18 times a year | 31st December 2005 |
| 7 | Nitrogen dioxide | 40 micrograms per cubic metre or less, when expressed as an annual mean | 31st December 2005 |
| 8 | PM10 | 50 micrograms per cubic metre or less, when expressed as a 24 hour mean, not to be exceeded more than 35 times a year | 31st December 2004 |
| 9 | PM10 | 40 micrograms per cubic metre or less, when expressed as an annual mean | 31st December 2004 |
| 10 | Sulphur dioxide | 350 micrograms per cubic metre or less, when expressed as an hourly mean, not to be exceeded more than 24 times a year | 31st December 2004 |
| 11 | Sulphur dioxide | 125 micrograms per cubic metre or less, when expressed as a 24 hour mean, not to be exceeded more than 3 times a year | 31st December 2004 |
| 12 | Sulphur dioxide | 266 micrograms per cubic metre or less, when expressed as a 15 minute mean, not to be exceeded more than 35 times a year. | 31st December 2005 |
For the purposes of this Schedule–
1. “PM10” means particulate matter which passes through a size-selective inlet with 50% efficient cut-off at 10 μm aerodynamic diameter.
2.—(1) A running annual mean is a mean which is calculated on an hourly basis, yielding one running annual mean per hour and the running annual mean for a particular substance at a particular location for a particular hour is the mean of the hourly levels for that substance at that location for that hour and the preceding 8,759 hours.
(2) For the purpose of the calculation of a running annual mean, the hourly level for a particular substance at a particular location is either–
(a)the level at which that substance is recorded as being present in the air at that location during the hour on the basis of a continuous sample of air taken during that hour for at least 30 minutes; or
(b)the mean of the levels recorded at that location on the basis of 2 or more samples of air taken during the hour for an aggregate period of at least 30 minutes.
3. A running 8 hour mean is a mean which is calculated on an hourly basis, yielding one running 8 hour mean per hour and the running 8 hour mean for a particular substance at a particular location for a particular hour is the mean of the hourly means for that substance at that location for that hour and the preceding 7 hours.
4.—(1) Subject to sub paragraph (2) below, an annual mean is a mean which is calculated on a yearly basis, yielding one annual mean per calendar year.
(2) The annual mean for a particular substance at a particular location for a particular calendar year is–
(a)in the case of lead, the mean of the daily levels for that year;
(b)in the case of nitrogen dioxide, the mean of the hourly means for that year;
(c)in the case of PM10, the mean of the 24 hour means for that year.
(3) For the purpose of the calculation of an annual mean for lead, the daily level for lead at a particular location for a particular day is the level at which lead is recorded as being present in the air at that location during the week in which the day occurs on the basis of a continuous sample of air taken throughout that week (each day in that week therefore being attributed with the same daily level).
(4) For the purpose of sub paragraph (3) above, “week” means a complete week beginning on a Monday, except that it also includes any period of less than seven days from the beginning of the calendar year until the first Monday in that year or from the beginning of the last Monday in the calendar year to the end of that year.
5. An hourly mean is a mean calculated every hour and the hourly mean for a particular substance at a particular location for a particular hour is the mean of the levels recorded, at a frequency of not less than once every 10 seconds, for that substance at that location during that hour.
6. A 24 hour mean is a mean calculated every 24 hours and the 24 hour mean for a particular substance at a particular location for a particular 24 hour period is the level at which that substance is recorded as being present in the air at that location on the basis of a continuous sample of air taken throughout the period.
7. A 15 minute mean is a mean calculated every 15 minutes and the 15 minute mean for a particular substance at a particular location for a particular 15 minute period is the mean of the levels recorded, at a frequency of not less than once every 10 seconds, for that substance at that location during that 15 minute period.
8. The reference to a number of micrograms or milligrams per cubic metre of a substance is a reference to the number of micrograms or milligrams per cubic metre of that substance when measured with the volume standardised at a temperature of 293(K and at a pressure of 101.3 kilopascals.