The Air Quality Limit Values (Wales) Regulations 2002

PART II NITROGEN DIOXIDE (NO₂) AND OXIDES OF NITROGEN (NO_x)

Limit values for nitrogen dioxide and oxides of nitrogen

2.1  

	Averaging period	Limit value	Margin of tolerance	Date by which limit value is to be met
1.  Hourly limit value for the protection of human health	1 hour	200 μg/m3 NO2, not to be exceeded more than 18 times a calendar year	70 μg/m3 on 1st January 2003, reducing on 1st January of each following year by equal annual amounts to reach 0 μg/m3 by 1st January 2010	1st January 2010
2.  Annual limit value for the protection of human health	Calendar year	40 μg/m3 NO2	14 μg/m3 on 1st January 2003, reducing on 1st January of each following year by equal annual amounts to reach 0 μg/m3 by 1st January 2010	1st January 2010
3.  Annual limit value for the protection of vegetation	Calendar year	30 μg/m3 NOx	None

Alert threshold for nitrogen dioxide

2.2  400 μg/m3 measured over three consecutive hours at locations representative of air quality over at least 100 km² or an entire zone or agglomeration, whichever is the smaller.

Minimum details to be made available to the public when the alert threshold for nitrogen dioxide is exceeded

2.3  Details to be made available to the public should include at least:

• the date, hour and place of the occurrence and the reasons for the occurrence, where known;

• any forecasts of:

  • changes in concentration (improvement, stabilisation, or deterioration), together with the reasons for those changes,

  • the geographical area concerned,

  • the duration of the occurrence;

  • the type of population potentially sensitive to the occurrence;

  • the precautions to be taken by the sensitive population concerned.