Thanks @DavecUK !
I was/am thinking of using a WYE (y duct). The reason for the WYE was/is: 1) to push smoke up the duct, 2) to protect the fan by not placing it directly in the duct run, 3) to not directly (or indirectly) pull air from the air roast chamber, which might impact air pressure within the roasting chamber (or otherwise impact the performance of the chamber). What are your thoughts on this approach?
Fyi, the fan is an inexpensive 100 CFM duct fan. The 8” to 4” duct reducer (effectively a rounded hood) will need to be directly above the roast chamber exhaust, to avoid smoke escape.
I can place the fan either directly on top of the hood or further up (1, 2 or 3 feet) up the duct run. Which is better? Thoughts?
I then have 2 options for ducting. Fully flexible 4” foil dryer duct? Or semi-flexible/rigid aluminum duct? Or both? I was initially concerned about heat/temperature so I was planning to start the duct run with the above mentioned hood, connected to semi-flexible aluminum (which can handle heat), connected to the fully flexible aluminum foil duct, connected to a dryer vent placed in my window. The total length of the duct run is about 5 feet.
But I would prefer to just use foil duct, as it is more flexible and easy to work with. Its also easier to move a hood (that is connected to fully flexible foil duct) up and out of the way, when not in use. This will allow my workbench to be used for multiple purposes. If it is absolutely safe. Safety is key. So what is the right/safe duct material to use?
Question: Is the above an appropriate approach? Overall? What’s the easiest but right way to do this?