Measurement and Monitoring of Carbon Monoxide
- Since 1972, carbon monoxide has been measured by the
Department of the Environment on a continuous basis for
varying periods of time at a total of 26 sites in the
United Kingdom. In the earlier years, up until 1979, the
method of measurement was liable to suffer interference
from atmospheric carbon dioxide and water vapour so these
records are not always comparable with those obtained
more recently. Currently 18 sites are in operation in the
United Kingdom measuring carbon monoxide, using infra-red
absorption, to an accuracy of +/- 8% and a precision of
0.6 ppm1. There are
four sites in London and one each in Glasgow, Manchester,
Sheffield, Cardiff, Belfast, Birmingham, Hull, Leicester,
Edinburgh, Liverpool, Leeds, Bristol, Southampton and
Newcastle upon Tyne. The Government has made commitments
to continue the expansion of this monitoring to all major
cities in the United Kingdom by 1997.
- From available measurements, it is possible to
conclude that levels of carbon monoxide are highest at
kerbside sites and in urban areas where traffic sources
predominate. As an example of the concentrations found
when continuous measurements are averaged over varying
time periods, Table 3 illustrates
the results of monitoring during recent years at some of
the urban sites. Detailed results of all United Kingdom
monitoring up until 1991 are available in the first
report of the Quality of Urban Air Review Group and to
March 1993 in Warren Spring Laboratory's annual data
summary of air pollution data in the United Kingdom.
Table 3 Carbon monoxide
monitoring data for the calendar years 1990-92
(ppm)
|
Site
|
Year
|
Annual average
|
Maximum 1-hour
|
Maximum 8-hour running average
|
Number of days the recommended EPAQS Standard
was exceeded
|
|
Stevenage
|
1990
1991
1992
|
0.7
0.7
0.6
|
6.4
7.4
5.0
|
3.5
4.9
3.0
|
0
0
0
|
|
London, Victoria
|
1990
1991
1992
|
1.3
1.4
1.0
|
11.7
13.9
9.3
|
10.2
11.2
6.6
|
1
3
0
|
|
London, Cromwell Road
|
1990
1991
1992
|
2.9
3.3
2.3
|
18.4
18.7
11.0
|
15.5
13.9
8.7
|
5
5
0
|
|
London, Earls Court
|
1990
1991
1992
|
1.5
1.7
1.1
|
13.2
18.0
8.7
|
10.2
15.8
6.3
|
3
4
0
|
|
London, Bloomsbury
|
1992
|
0.8
|
5.8
|
4.5
|
0
|
|
Glasgow
|
1990
1991
1992
|
1.1
1.4
1.0
|
17.0
16.3
11.2
|
11.6
12.5
8.7
|
2
3
0
|
|
Manchester
|
1991
1992
|
0.9
0.9
|
8.6
15.7
|
5.7
12.5
|
0
2
|
|
Sheffield
|
1991
1992
|
0.9
0.7
|
8.3
9.3
|
6.3
7.4
|
0
0
|
|
Belfast Centre
|
1992
|
0.7
|
18.1
|
10.3
|
1
|
|
Birmingham Centre
|
1992
|
0.6
|
14.2
|
10.8
|
1
|
|
Cardiff Centre
|
1992
|
0.7
|
9.6
|
4.9
|
0
|
|
Edinburgh Centre
|
1992
|
0.9
|
6.1
|
3.7
|
0
|
|
Newcastle Centre
|
1992
|
0.8
|
8.2
|
4.0
|
0
|
- Figures 2and 3
illustrate the maximum concentrations recorded at different sites
in the United Kingdom in each month of the year. Figure
2 presents these data for readings averaged over one hour, while
Figure 3 shows averages over eight hours as running means. In each figure, line represents the World Health Organization air quality guideline; 5 ppm for the 1-hour average and ppm for the 8-hour average. It can be seen that the 8-hour average imposes the stricter guideline, in that the 1-hour value is rarely, if ever, exceeded. These figures also show the increased levels associated with winter climatic conditions. Nowadays, in the United Kingdom, 1-hour average values do not exceed 25%ppm.1 1
part per million (ppm) is one part, by volume, in one million or in
106 . 1 ppm of carbon monoxide is 1.165 mg/m3
at 20oC and 1013 millibars.
[Note - the previous paragraph may have suffered some corruption but has been recovered as far as possible.]
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Published 29 October 1998
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