2010 Issue

36 For decades, engineers and scientists have had to visually observe plumes of smoke to determine the amount, or opacity value, of pollutants coming out of smoke stacks. I N 2004 HILL AIR FORCE Base (AFB) environ- mental engineers began looking into a means to remove the subjectivity of the human eye , increase the defensibility of the levels observed, and reduce the cost of doing visible emission observations (using the Environmental Protection Agency’s Method 9), that they were required to do under the base’s Title V permit. The Hill engineers decided the best way to do this was with the use of digital cameras to document visible emissions at the source of a smoke release into the air to support Method 9 opacity observations. In partnership with industry, the Hill group produced the Digital Opacity Compliance SystemSecondGeneration (DOCS II) system, and began testing to ensure that digital images of visible emissions could both document visible emission observations as well as calculate their opacity values. Figure 1 provides a view of the DOCS II performing analysis of smoke from a smoke generator at a smoke school. This government industry partnership continued to test DOCS II to verify and validate that under all conditions, DOCS II could measure visible emission opacity as well as the human Method 9-certified observers required by the EPA. Figure 2 depicts the results of a smoke school test whereby DOCS II results (Blue) are directly compared to humanMethod 9 readers (Red), by comparing both to an in-stack transmissometer Figure 1- DOCS II at Smoke School ASTM as a Means to Regulatory Change STEVE RASMUSSEN Hill Air Force Base (Yellow) whichmeasures the same smoke plumes at the same time observers and DOCSII record their respective opacities. This figure illustrates that DOCS II can indeed measure visible emission opacity as well or bet- ter than humanMethod 9 certified readers when compared to a calibrated transmissometer in smoke school. Problem Once it was proven that DOCS II could perform visible emission observations as well or better than humanMethod 9 readers, Hill AFB took the solution to the regulatory community to have the technology adopted as an alternate test method to Method 9, that is required to be used under the Clean Air Act. Upon collaboration with regu- latory leaders in the EPA EmissionMeasurement Center (EMC), various EPA regional offices and state enforcement agencies, it was determined that a consensus standard from the American Society for Testing and Materials (ASTM) D22 (Air Quality) committee would be needed. To get this consensus standard, a work group was formed in September 2007. To Certify, or Not to Certify? One critical consideration for the work group was certification. While re-certification every six months, as currently required for humans in the EPA’s Method 9 is a cost burden, some level of certification would be necessary because: • Model of the camera could contribute to variability of results; • Computer platform could contribute to variability of results; • Software modifications affecting the analysis tools would impact results; and, • An ASTM standard itself would drive new technological solutions which must also be certified.