Office of Public Sector Information
SCHEDULE 7 continued PART 3
6. The following information shall be compiled for zones within which sources other than fixed measurement are employed to supplement information from measurement—
(a) a description of the assessment activities carried out;
(b) specific methods used, with references to descriptions of the method;
(c) sources of data and information;
(d) a description of results, including uncertainties and, in particular, the extent of any area within the zone over which concentrations exceed long-term objectives or target values; and
(e) for the long-term objective and target value for the protection of human health, the population potentially exposed to concentrations in excess of the threshold.
7. The Secretary of State shall ensure that maps are compiled showing concentration distributions within each zone.
Regulation 16(2)Regulation 17(2)(d)
Group A pollutants (other than benzene and carbon monoxide) and PM2.5
1. The data-quality objectives set out in the following table, for the required accuracy of assessment methods, of minimum time coverage and of data capture of measurement are laid down to guide quality assurance programmes—
| Sulphur dioxide, nitrogen dioxide and oxides of nitrogen | Lead, PM2.5 and PM10 | |
|---|---|---|
| Continuous measurement | ||
| Accuracy | 15% | 25% |
| Minimum data capture | 90% | 90% |
| Indicative measurement | ||
| Accuracy | 25% | 50% |
| Minimum data capture | 90% | 90% |
| Minimum time coverage | 14% (One measurement a week at random, evenly distributed over the year, or eight weeks evenly distributed over the year) | 14% (One measurement a week at random, evenly distributed over the year, or eight weeks evenly distributed over the year) |
| Modelling | ||
| Accuracy: | ||
| Hourly averages | 50%–60% | |
| Daily averages | 50% | |
| Annual averages | 30% | 50% |
| Objective estimation | ||
| Accuracy | 75% | 100% |
2. The accuracy of the measurement is defined as that set out in the ‘Guide to the Expression of Uncertainty of Measurements’ (ISO 1993)(19) or in ISO 5725-1 ‘Accuracy (trueness and precision) of measurement methods and results’ (ISO 1994). The percentages in the table are given for individual measurements averaged, over the period considered, by the limit value, for a 95% confidence interval (bias + two times the standard deviation). The accuracy for continuous measurements shall be interpreted as being applicable in the region of the appropriate limit value.
3. The accuracy for modelling and objective estimation is defined as the maximum deviation of the measured and calculated concentration levels, over the period considered by the limit value, without taking account the timing of the events
4. The requirements for minimum data capture and time coverage do not include losses of data due to the regular calibration or the normal maintenance of the instrumentation.
5. The Secretary of State may allow for random measurements to be made instead of continuous measurements for lead, PM2.5 and PM10 by methods for which accuracy within the 95% confidence interval with respect to continuous monitoring has been demonstrated to be within 10%. Random sampling shall be spread evenly over the year.
6. 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—
| Benzene | Carbon monoxide | |
|---|---|---|
| Fixed measurements | ||
| Uncertainty | 25% | 15% |
| Minimum data capture | 90% | 90% |
| Minimum time coverage | 35% urban background and traffic sites (distributed over the year to be representative of various conditions for climate and traffic); 90% industrial sites | |
| Indicative measurements | ||
| Uncertainty | 30% | 25% |
| Minimum data capture | 90% | 90% |
| Minimum time coverage | 14% (one day’s measurement a week at random, evenly distributed over the year, or eight weeks evenly distributed over the year) | 14% (one measurement a week at random, evenly distributed over the year, or eight weeks evenly distributed over the year) |
| Modelling | ||
| Uncertainty: | ||
| Eight-hour averages | 50% | |
| Annual averages | 50% | |
| Objective estimation | ||
| Uncertainty | 100% | 75% |
7. The uncertainty (on a 95% confidence interval) of the assessment methods shall be evaluated in accordance with the ‘Guide to the Expression of Uncertainty of Measurements’ (ISO 1993) or the methodology of ISO 5725:1994. The percentages for uncertainty in the table in paragraph 6 are given for individual measurements averaged over the period considered by the limit value, for a 95% confidence interval. The uncertainty for the fixed measurements shall be interpreted as being applicable in the region of the appropriate limit value.
8. The uncertainty for modelling and objective estimation is defined as the maximum deviation of the measured and calculated concentration levels, over the period considered by the limit value, without taking into account the timing of the events.
9. The requirements for minimum data capture and time coverage do not include losses of data due to the regular calibration or the normal maintenance of the instrumentation.
10. The Secretary of State may allow for random measurements to be made instead of continuous measurements for benzene if the uncertainty, including the uncertainty due to random sampling, meets the quality objective of 25%. Random sampling shall be spread evenly over the year.
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The Air Quality Standards Regulations 2007