The Air Quality Limit Values Regulations (Northern Ireland) 2002 No. 94

Regulation 7(4)

SCHEDULE 4 Criteria for Determining Minimum Numbers of Sampling Points for Fixed Measurement of Concentrations of Relevant Pollutants in Ambient Air.

PART I MINIMUM NUMBER OF SAMPLING POINTS FOR FIXED MEASUREMENT TO ASSESS COMPLIANCE WITH LIMIT VALUES FOR THE PROTECTION OF HUMAN HEALTH AND ALERT THRESHOLDS IN ZONES AND AGGLOMERATIONS WHERE FIXED MEASUREMENT IS THE SOLE SOURCE OF INFORMATION

Diffuse sources

Population of agglomeration or zone (thousands)	If concentrations exceed the upper assessment threshold	If maximum concentrations are between the upper and lower assessment thresholds	For SO2 and NO2 in agglomerations where maximum concentrations are below the lower assessment thresholds
0–250	1	1	not applicable
250–499	2	1	1
500–749	2	1	1
750–999	3	1	1
1 000–1 499	4	2	1
1 500–1 999	5	2	1
2 000–2 749	6	3	2
2 750–3 749	7	3	2
3 750–4 749	8	4	2
4 750–5 999	9	4	2
> 6 000	10	5	3
For NO2 and particulate matter: to include at least one urban-background station and one traffic-orientated station

Point sources

(b) For the assessment of pollution in the vicinity of point sources, the number of sampling points for fixed measurement should be calculated taking into account emission densities, the likely distribution patterns of ambient-air pollution and the potential exposure of the population.

PART II MINIMUM NUMBER OF SAMPLING POINTS FOR FIXED MEASUREMENTS TO ASSESS COMPLIANCE WITH LIMIT VALUES FOR THE PROTECTION OF ECOSYSTEMS OR VEGETATION IN ZONES OTHER THAN AGGLOMERATIONS

If maximum concentrations exceed the upper assessment threshold	If maximum concentrations are between the upper and lower assessment thresholds
In island zones the number of sampling points for fixed measurement should be calculated taking into account the likely distribution patterns of ambient air pollution and the potential exposure of ecosystems or vegetation.
1 station every 20 000 km2	1 station every 40 000 km2