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WEB PAGES - ABOUT
1. Smoke School, Opacity, & Visible Emission
   Smoke school programs nationwide for government, industry, and consultants. At our smoke schools opacity observers are trained and receive certification to determine the opacity of visible ...
   www.eta-is-opacity.com
   
   
2. SHORT HISTORY OF VISIBLE EMISSIONS & OPACITY
   HISTORY OF OPACITY. EARLY HISTORY In 1273 Edward I (Longshanks) of England prohibited the burning of coal.
   www.eta-is-opacity.com/history.htm