The information was based on Environment Agency data which compared check monitoring results for each substance with the emission limit. The data did not specify the sampling period on which the limit was based.
In the article, we mistakenly said that levels of oxides of nitrogen were found to be 20 times above permitted levels. In fact, we meant to refer to carbon monoxide.
Carbon monoxide levels were found to be 1,045mg/m3 measured over a 2-hour period. This should have been compared to a limit of 100mg/m3 as a 10 minute average, rather than a daily average of 50mg/m3. Nevertheless, this was still an apparent breach of the authorised limit.
We also said that levels of sulphur dioxide were found by check monitoring to be 212mg/m3 as a 2-hour average - four times authorised levels. In fact, the reading should have been compared to a half-hourly average of 200mg/m3, rather than the daily average of 50mg/m3.