LegalizeThe Air Quality Limit Values Regulations 2003
The following data quality objectives, 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 8 weeks evenly distributed over the year) | 14% (one measurement a week at random, evenly distributed over the year, or 8 weeks evenly distributed over the year) |
| Modelling | ||
| Uncertainty: | 50% | |
| Eight-hour averages | 50% | |
| Annual averages | ||
| Objective estimation | ||
| Uncertainty | 100% | 75% |
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*rsquo; (ISO 1993) or the methodology of ISO 5725:1994 . The percentages for uncertainty in the above table 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 should be interpreted as being applicable in the region of the appropriate limit value.
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.
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.
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 must be spread evenly over the year.
The following information should be compiled for zones within which sources other than measurement are employed to supplement information from measurement or as the sole means of air quality assessment:
- — a description of assessment activities carried out;
- — the specific methods used, with references to descriptions of the method;
- — the sources of data and information;
- — a description of results, including accuracies and, in particular, the extent of any area or, if relevant, the length of road within the zone over which concentrations exceed the limit value or, as may be, the limit value plus applicable margin of tolerance and of any area within which concentrations exceed the upper assessment threshold or the lower assessment threshold;
- — for limit values the object of which is the protection of human health, the population potentially exposed to concentrations in excess of the limit value.
Where possible maps shall be compiled showing concentration distributions within each zone.
The following data quality objectives, for allowed uncertainty of assessment methods, and of minimum time coverage and of data capture of measurement, are provided to guide quality-assurance programmes.
| For ozone, NO and NO₂ | |
|---|---|
| Continuous fixed measurement | |
| Uncertainty of individual measurements | 15% |
| Minimum data capture | 90% during summer75% during winter |
| Indicative measurement | |
| Uncertainty of individual measurements | 30% |
| Minimum data capture | 90% |
| Minimum time coverage | >10% during summer |
| Modelling | |
| Uncertainty | 50% |
| 1 hour averages (daytime) | 50% |
| 8 hours daily maximum | |
| Objective estimation | |
| Uncertainty | 75% |
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) of 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 should be interpreted as being applicable in the region of the concentration used for the appropriate threshold.
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.
‘Time coverage’ means the percentage of time considered for settling the threshold value during which the pollutant is measured.
‘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.
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.
The following information should be compiled for zones within which sources other than measurements are employed to supplement information from measurement:
- — a description of the assessment activities carried out;
- — specific methods used, with references to descriptions of the method;
- — sources of data and information;
- — 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;
- — for long-term objectives or target values whose object is the protection of human health, the population potentially exposed to concentrations in excess of the threshold.
The Secretary of State shall ensure that maps are compiled showing concentration distributions within each zone.
ISO/FDIS 10498 (Standard in draft) Ambient air—determination of sulphur dioxide—ultraviolet fluorescence method .
ISO 7996: 1985 Ambient air—determination of the mass concentrations of nitrogen oxides—chemiluminescence method .
The reference method for the sampling of lead will be that described in the Annex to Directive 82/884/EEC until such time as the limit value in Schedule 1 to these Regulations is to be met, when the reference method will be that for PM₁₀ specified in Part IV of this Schedule.
ISO 9855: 1993 Ambient air—Determination of the particulate lead content of aerosols collected in filters. Atomic absorption spectroscopy method .
The reference method for the sampling and measurement of PM₁₀ will be that described in EN 12341 ‘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.
The reference method for the measurement of benzene will be a pumped sampling method on a sorbent cartridge followed by gas chromatographic determination.
The reference method for the measurement of carbon monoxide will be a non-dispersive infra-red spectrometric (NDIR) method.
The reference method for analysis of ozone shall be the UV photometric method (ISO FDIS 13964 or equivalent).
The reference method for calibration of ozone instruments shall be the Reference UV photometer method (ISO FDIS 13964, VDI 2468, B1.6 or equivalent).
The following information on ozone concentrations shall be obtained and collated—
| Type of station | Level | Averaging/accumulation time | Provisional data for each month from April to September | Report for each year | |
|---|---|---|---|---|---|
| Information threshold | Any | 180µg/m³ | 1 hour | —for each day with any exceedance: date, total hours of exceedance, maximum 1 hour ozone and related NO₂ values when required—monthly 1 hour maximum ozone | —for each day with any exceedance: date, total hours of exceedance, maximum 1 hour ozone and related NO₂ values, when required |
| Alert threshold | Any | 240µg/m³ | 1 hour | —for each day with any exceedance: date, total hours of exceedance, maximum 1 hour ozone and related NO₂ values, when required | —for each day with any exceedance: date, total hours of exceedance, maximum 1 hour ozone and related NO₂ values, when required |
| Health protection | Any | 120µg/m³ | 8 hours | —for each day with any exceedance: date, 8 hours maximum (b) | —for each day with any exceedance: date, 8 hours maximum (b) |
| Vegetation protection | Suburban, rural, rural background | AOT40 (a) =6,000µg/m³.h | 1 hour, accumulated from May to June | Value | |
| Forest protection | Suburban, rural, rural background | AOT40 (a) =20,000µg/m³.h | 1 hour, accumulated from April to September | Value | |
| Materials | Any | 40 µg/m³ | 1 year | Value |
a
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In this Part, percentiles are to be calculated using the method specified in Council Decision 97/101/EC establishing a reciprocal exchange of information and data from networks and individual stations measuring ambient air pollution within Member States .
The following criteria are to be used for checking validity when aggregating data and calculating statistical parameters—
| Parameter | Required proportion of valid data |
|---|---|
| 1 hour values | 75% (45 minutes) |
| 8 hour values | 75% of values (6 hours) |
| Maximum daily 8 hours mean from hourly running 8 hours averages | 75% of the hourly running 8 hour averages(8 hours per day) |
| AOT40 | 90% of the 1 hour values over the time period defined for calculating the AOT40 value (a) |
| Annual mean | 75% of the 1 hour values over summer (April to September) and winter (January to March, October to December) seasons separately |
| Number of exceedances and maximum values per month | 90% of the daily maximum 8 hours mean value (27 available daily values per month) 90% of the 1 hour values between 8:00 and 20:00 Central European Time |
| Number of exceedances and maximum values per year | Five out of six summer months over the summer season (April to September) |
a
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Editorial notes
Regulations revoked (15.2.2007) by The Air Quality Standards Regulations 2007 (S.I. 2007/64), regs. 1(1), 32(1)(a)
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