Field Validation of Visible Opacity Photographic Systems

摘要

The Digital Opacity Compliance System (DOCS) is an innovative method that employs digital imaging technology for quantifying visible opacity. DOCS, which has been demonstrated to be a technically defensible and economically attractive alternative to the US Environmental(COTS) digital cameras to determine opacity. To date, all DOCS field testing has been conducted using two models of digital cameras, notably Kodak models DC265 and DC290, which are no longer commercially available. To ensure that DOCS technology users will have access to field validated and affordable digital cameras, the following flagship models of digital cameras were tested for DOCS system compatibility: 1) Sony Cybershot DSC-WI, 2) Nikon Coolpix 5200, 3) Fuji Finepix E500 and 4) Kodak model DX6490. Within the opacity range of regulatory interest, 0 to 40%, the Sony Cybershot DSC-WI and Nikon Coolpix 5200 digital cameras reported opacity readings that were 0.11% and 0.46% lower, respectively, than those measurements made through use of an EPA Method 9 smoke generator. These opacity differences were found to be statistically insignificant. The Fuji Finepix E500 reported visible opacity measurements that were, on average, 2.2% less-a difference that was determined to be statistically significant and unacceptable for regulatory reporting. The Kodak model DX6490, which was evaluated at an EPA-approved smoke school, was found to generate opacity measurements whose accuracy was statistically equivalent to the EPA certified in-stack transmissometer over the opacity range of 0 to 40%. As a result of the successful field validation of commercially available digital camera systems, the USEPA has proposed a new camera-based visible opacity measurement approach entitled "Determination of Visible Emission Opacity from Stationary Sources Using Computer-Based Photographic Analysis Systems"(URL Address: http://www.epa.gov/ttn/emc/prelim/pre- 008.pdf). The proposed approach is expected to be promulgated as a conditional method following closure of the public comment period.