As an example, the following case study was described: An aluminium pop can manufacturing facility. There were two sources of odour at this facility: the process where oil was washed off the cans, and the paint shops. In response to odour complaints, the local authority required the facility to conduct field measurements over a 6-month period. The odour frequency in residential areas was found to be 0.20, which is over the limit. So the local authority required the company to install controls on the paint facility (after burners). Results of a second field study indicated they still had an odour frequency of 0.20 odour hours, but this time it was due to the can washing process, the odour of which had previously been masked. The company was required to install additional control measures, in this case, drying the air. A third 6-month field study was conducted, and showed the odour frequency was less than 0.10. The whole process took five years. The public was kept informed about progress for the duration.