Office of Public Sector Information
SCHEDULE 8 continued PART 3
16. The data quality objectives set out in the following table, for allowed uncertainty of assessment methods, of minimum time coverage and of data capture of measurement, are provided to guide quality-assurance programmes—
| For ozone, NO and NO2 assessed at ozone sampling points | |
|---|---|
| Continuous fixed measurement | |
| Uncertainty of individual measurements | 15% |
| Minimum data capture | 90% during summer; 75% during winter |
| Indicative measurement | |
| Uncertainty of individual measurements | 30% |
| Minimum data capture | 90% |
| Minimum time coverage | >10% during summer |
| Modelling | |
| Uncertainty: | |
| 1 hour averages (daytime) | 50% |
| 8 hours daily maximum | 50% |
| Objective estimation | |
| Uncertainty | 75% |
17. The uncertainty (on a 95% confidence interval) of the measurement methods shall be evaluated in accordance with the principles laid down in the ‘Guide to the Expression of Uncertainty of Measurements’ (ISO 1993), or the methodology in ISO 5725-1 ‘Accuracy (trueness and precision) of measurement methods and results’ (ISO 1994) or equivalent. The percentages for uncertainty in the table are given for individual measurements, averaged over the period for calculating target values and long-term objectives, for a 95% confidence interval. The uncertainty for continuous fixed measurements shall be interpreted as being applicable in the region of the concentration used for the appropriate threshold.
18. The uncertainty for modelling and objective estimation means the maximum deviation of the measured and calculated concentration levels, over the period for calculating the appropriate threshold, without taking into account the timing of events.
19. “Time coverage” means the percentage of time considered for settling the threshold value during which the pollutant is measured.
20. “Data capture” means the ratio of the time for which the instrument produces valid data, to the time for which the statistical parameter or aggregated value is to be calculated.
21. The requirements for minimum data capture and time coverage do not include losses of data due to the regular calibration or normal maintenance of the instrumentation.
Regulation 16(3)(a)
| Reference method | |
|---|---|
| Sampling and measurement of benzene | EN 14662: 2005, Parts 1, 2 and 3 ‘Ambient air quality - Standard method for measurement of benzene concentrations’ |
| Analysis of carbon monoxide | EN 14626: 2005 ‘Ambient air quality – Standard method for the measurement of the concentration of carbon monoxide by nondispersive infrared spectroscopy’ |
| Sampling of lead | The same reference method as for PM10 |
| Analysis of lead | ISO 9855: 1993 Ambient air — Determination of the particulate lead content of aerosols collected in filters. Atomic absorption spectroscopy method |
| Analysis of nitrogen dioxide and oxides of nitrogen | ISO 7996: 1985 Ambient air — determination of the mass concentrations of nitrogen oxides — chemiluminescence method |
| Sampling and measurement of PM10 | EN 12341: 1998 “Air Quality — Field Test Procedure to Demonstrate Reference Equivalence of Sampling Methods for the PM10 fraction of particulate matter” . The measurement principle is based on the collection on a filter of the PM10 fraction of ambient particulate matter and the gravimetric mass determination |
| Analysis of sulphur dioxide | ISO/FDIS 10498 (Standard in draft) Ambient air — determination of sulphur dioxide — ultraviolet fluorescence method |
The Air Quality Standards Regulations 2007