Bill Harrison's pictures are among the most compelling I've seen posted - worth their weight in gold, in my opinion. As attractive as vent systems B and C in Cadia's post are, I've never been willing to either use one myself, build one for myself, or advocate one because of these pictures and the supporting science that predicts them. From the smoke tests I've seen posted by people with vent system A in Cadia's post, the tests appear to support the analysis that goes behind the design of these vent systems and the fact that they don't seem to have much turbulence (if they have sides to the table).
Cadia's picture for A is a little misleading in that the fan, as she's drawn the vent duct, would draw more from the back of the hood, not uniformly downward under the whole hood. The actual laminar flow of the plume to the hood exit would therefore be more diagonal, away from the face. This can be seen in the smoke test videos folks have posted with that kind of system. That said, and being short in the saddle, I've wondered if there aren't improvements that can be made to this classic design, like a 'sneeze guard' - I've seen those on chemical vent hoods.
Regardless, I'm open to learning something new, so I'm looking forward to seeing Acidfly's side shots as soon as the weather cooperates for him.
Linda
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