The DustScan computer-based scanning and analysis system, based on the use of sticky pads, was specifically designed for dust annoyance assessment and is far more sensitive than many other methods. This method originated at the University of Leeds in the 1990s, and was refined, developed and validated through a series of research projects.
Each sample received is sealed (to encapsulate the dust and protect the sample from contamination) labelled and given a unique identifier in a secure database. The sample is then scanned and the image processed using in-house software to generate the Absolute Area Coverage (AAC) and Effective Area Coverage (EAC) for the sample. Both AAC and EAC are expressed as percentages. %AAC is unique to DustScan; %EAC was first developed in the 1980s to measure dust soiling and the version was adapted by the firm in the early 2000s. A newer, digital approach is taken covering the entire spectrum (from white to black) in contrast to the earlier ‘analogue’ methods of measuring greyscale such as with a smoke-stain reflectometer.
- %AAC is the coverage of dust, irrespective of colour. So long as it can be seen it in the scanned image, any dust, pale or dark can be recorded as AAC. As a result AAC is a very sensitive measure and is especially effective in detecting low levels of dust which might not show up by other sampling techniques.
- %EAC is the darkness or greyscale discolouration of dust and is used as a measure of dust soiling. Unlike AAC, EAC is a measure of the darkness, or soiling caused by dust so for the same colour dust (be it chalk or coal), %EAC generally increases with dust coverage.
In combination, DustScan has developed a widely-recognised dust annoyance ‘risk assessment’ protocol, combining dust coverage as %AAC and dust soiling as %EAC. For directional samples, increased ‘dust annoyance risk’ indicates increased potential for dust annoyance in the direction shown; for depositional samples, increased ‘risk’ indicates potential for dust annoyance at that location.