In January 2012, the VT LLC team set out to devise a means to certify DOCS II SaaS ability to determine opacity of fugitive emissions, as well as, stationary sources. Using the ASTM standard process as a guide the team devised a certification test that utilized actual fugitive road dust as essentially another color of the institutionalized Method 9 (25 White and 25 Black) testing. Thus the certification would require the analysis of 25 Dust (color) opacity readings ranging from 0 to 100% opacity. To facilitate the experiment VT LLC set up a Long Path Transmissometer, (LPT) that was calibrated in accordance with NIST procedures and approved filters before and after each “Dust Run”. The LPT was situated perpendicular to the dirt road surface and 3.5’ above the surface, such that a vehicle traveling down the road and generating a dust cloud would pass through the LPT. This passing through the LPT triggered the event to start, the LPT would then record opacity values in one second intervals, until it was reset. Aligned with the transmissometer were three digital image devices, 1) a common G11, 2) a Nikon D3100, and 3) a Sony High Definition Digital Recorder (HDR). All 4 devices, (the LPT and the 3 image devices) were connected to a common timing device such that a single trigger (vehicle passing through the LPT) would simultaneously fire all four devices, which would record data every second as possible.

The ASTM dust experiment proved many of VT LLC’s theories of Dust opacity capture. First, standard digital cameras like the Cannon G11 do not refresh fast enough to record dust opacity every second and even 5 seconds is a stretch. High speed digital cameras like the Nikon D3100 with burst mode where able to refresh fast enough, and HDR’s were clearly the best device for recording highly transient Dust opacity. Second, when determining dust opacity averaging of multiple frames of images provided by the Nikon Cameras and HDR’s drove the error rates down to +/- 3% matching the calibration of the LPT. Finally, the back scatter of the LPT laser imaged as it passed through the dust cloud seemed to show the ability to characterize the size of the particulate in the dust.

DOCS II SaaS was used extensively during the ASTM Dust test to prove its reliability and field data collection benefits. The data from this test was used to rewrite the ASTM D7520-09 and submit a new version to ballot, that would allow the use of multiple image capture devices. ASTM D7520-12 was approved in October 2012 allowing the use of multiple image capture devices, most importantly HDR devices.