Visible emission opacity estimation using the Optical Digital Environmental Compliance System as an alternative to the Environmental Protection Agency's Reference Method 9

The Optical Digital Environmental Compliance System (ODECS) is a digital camera and computer software system designed to be an alternative to the human observer in EPA's Reference Method 9. ODECS was tested at several different locations under varying meteorological conditions during EPA Reference Method 9 human observer certification runs. Using a one-sample Student t-test revealed that the ODECS is not able to measure the opacity of smoke plumes as accurately as a certified human observer. The testing revealed that ODECS was able to measure the true opacity of black smoke plumes far better than white smoke plumes, particularly for plumes above 45 percent opacity. Additionally, the ODECS was able to more accurately measure opacities under clear sky conditions than under cloudy or partly-cloudy conditions. The ODECS is a promising technology that requires further refinements before it can be considered a viable alternative to the human observer in Reference Method 9.