The Air Quality (Wales) Regulations 2000

Regulations 2, 3 and 4

THE SCHEDULE

PART I

TABLE

AIR QUALITY OBJECTIVES

Substance/ Air Quality Objective levels	Date by which objective to be achieved
Benzene: 16.25 micrograms per cubic metre or less, when expressed as a running annual mean	31 December 2003
1, 3 -Butadiene: 2.25 micrograms per cubic metre or less, when expressed as a running annual mean	31 December 2003
Carbon monoxide: 11.6 milligrams per cubic metre or less, when expressed as a running 8 hour mean	31 December 2003
Nitrogen dioxide: 200 micrograms per cubic metre or less, when expressed as an hourly mean, not to be exceeded more than 18 times a year	31 December 2005
Nitrogen dioxide: 40 micrograms per cubic metre or less, when expressed as an annual mean	31 December 2005
Lead: 0.5 micrograms per cubic metre or less, when expressed as an annual mean	31 December 2004
Lead: 0.25 micrograms per cubic metre or less, when expressed as an annual mean	31 December 2008
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	31 December 2004
PM10 40 micrograms per cubic metre or less, when expressed as an annual mean	31 December 2004
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	31 December 2004
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	31 December 2004
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	31 December 2005

PART II

Interpretation

For the purposes of this Schedule:

1.—(1) A running annual mean is a mean which is calculated on an hourly basis, yielding one running annual mean per hour. The running annual mean for a 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 8759 hours.

(2) For the purpose of the calculation of a running annual mean, the hourly level for a 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.

2.  A running 8 hour mean is a mean which is calculated on an hourly basis, yielding one running 8 hour mean per hour. The running 8 hour mean for a 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.

3.—(1) An annual mean is a mean which is calculated on a yearly basis, yielding one annual mean per calendar year. The annual mean for a 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; and

(c) in the case of PM₁₀, the mean of the 24 hour means for that year.

(2) For the purpose of the calculation of the 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).

(3) “PM₁₀” means particulate matter which passes through a size-selective inlet with a 50% efficiency cut-off at 10μm aerodynamic diameter.

(4) For the purpose of sub-paragraph (2), “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.

4.  An hourly mean is a mean calculated every hour. The hourly mean for a 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.

5.  A 24 hour mean is a mean calculated every 24 hours. The 24 hour mean for a 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.

6.  A 15 minute mean is a mean calculated every 15 minutes. The 15 minute mean for a substance at a particular location for a particular 15 minutes 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 minutes.

7.  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 kPa.