NCDENR
North Carolina Department of Environment and Natural Resources
Division of Air Quality
Michael F. Easley, Governor William G. Ross Jr., Secretary
Alan W. Klimek, Director
Corrigenda: 1999 Ambient Air Quality Report
In a fresh review of carbon monoxide data, we have discovered several errors in a5.4 of our 1999
annual report. Perhaps the most serious of these was overlooking the fact that the statewide
highest concentrations that were reported for the monitor in Chapel Hill occurred during a
structure fire in the vicinity of the monitor, so that they are “exceptional events”, rather than
valid ambient data as we originally reported.
Corrected versions of Table 5.4, Figure 5.8 and Figure 5.9 are attached, and corrections to the
text are as follows:
Page v, Is' paragraph:
CO was sampled at 12 sites, yielding 77,960 valid hourly averages. The National Ambient Air
Quality Standards for CO are 35 ppm for the maximum one-hour average and 9 ppm for the
maximum eight-hour average. There were no exceedances of the standards, although the
highest one hour concentration of 8.5 (25 percent of the standard) was observed at the College
Street site in Wilmington and highest eight-hour concentration of 5.8 (65 percent of the
standard) was observed at the North Roxboro Street site in Durham. Both the mean one-hour
average and the mean eight-hour average have been decreasing by about 4 percent per year.
The combined effects of newer cars in the vehicle fleet, traffic control strategies, and the
Inspection and Maintenance Program in Durham, Orange, Wake, Forsyth, Guilford, Cabarrus,
Gaston, Mecklenburg, and Union Counties have helped reduce the number and intensity of CO
exceedances from previous years.
Page 29, 4lh paragraph:
There were no exceedances of the CO
ambient air quality standards in 1999. The
highest 1-hour average was 21 .5 parts per
million (ppm), which occurred at the East
Franklin Street, Chapel Hill site on
November 5, during a structure fire that
Ambient Monitoring Section
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