You can make a plenum out of plywood and line it with metal foil backed insulation to dampen noise. I use a vacuum plenum box with a squirrel cage fan for my main ventilation.
The hole in my bench is made to fit a 10 inch duct. It's covered with a standard return air duct like you would put over a big return air vent in a wall. If you bend the louvers on it slightly you can have some effect of the direction of the air flow.
I've got mine set to send most of the air goes straight up.
For the most part I don't notice much change in the atmosphere under the hood unless it's either extremely hot or cold outside. I have a thermometer in my vacuum plenum and the temp stays pretty close to outside ambient most of the time. I run a GGT Mirage and will see a small uptick in temp in the box if I run the outer ring for a long time. I don't do that a lot, but I do keep an eye on the plenum temp when I do so that nothing overheats.
Robert
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Robert Simmons
(Former) Director for Bead Donations
Beads of Courage, Inc.
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