Needless to say the customer was extremely upset with the inspection process, blaming the inspection lane driver and test equipment for the initial failure. I nspection and Maintenance programs are intended to separate vehicles with excessive emissions from relatively clean vehicles. However, inadequate preconditioning of some vehicles prior to emissions testing can cause inaccurate or inconsistent test results. However, it is an issue when a vehicle initially tests at 32 gpm CO and then passes on the retest with no repairs performed. That is not to say that you will not get some test variability between different drivers.
Some drivers can drive the trace a little better than others.
Overall, however, the difference in test readings is relatively small. Again, it is easy to blame test equipment. An extensive quality assurance program is also performed on each lane by specially trained Department of Revenue personnel. If the equipment is a variable, it is very small. The vehicle is constantly changing before and during testing.