Section 1.3
Visible Emissions & Opacity Defined
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The terms “visible emissions” and “opacity” will be used frequently throughout this course. Let’s take a look at exactly what they mean.
Visible Emissions
A visible emission is the visible particulate matter that occurs as the result of a process. Smoke exiting a stack at a power plant is a visible emission
Dust produced from driving down a gravel road is a visible emission
Smoke from the chimney of your fireplace is a visible emission
Opacity
When you’re talking about visible emissions, opacity is the degree to which light is blocked by the emissions. When you are observing emissions there is always a background behind the smoke plume. This background can be anything, but ideally it should contrast with the emissions you are observing.
Tree as a background
Sky as a background
Building as a background
Video Demonstration of Opacity