Passive vents size

10x16 shed I am foaming and ducting out a main 8 inch metal duct with 4 6inch tap offs for 4 tents. My question is what size passive intakes should I cut in the shed if I’m exhausting from each tent to a main duct out of the building. The exhaust fans will be 2 4” and 2 6”

What kind of lights are you using

joesoap2013 said:

What kind of lights are you using

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Led ac infinity bar lights

If the four extractors are going to an 8 outlet duct surely it would be 8 in lol
I'm baked shouldn't a opened my mouth lol

If I have you right you have 4 tents with 2 6 inches and 2 4inchs connected to an 8 out
I'd go 8 in and duct intake same size as the extractor
So if its a 4 inch out put a 4 inch duct intake in
Run 4 ducts from the 8 inch in

I used 6" ductwork for the filters on 2 spaces and I have an 8” passive line in, but it's still pulling negative pressure with it and I have a 4" I can increase the input to if I need it.
I'd suggest double the area for your input with an adjustable blast gate if you need that option..

I've always used the double formula.
So 1 fan that has a diameter of 10 inches would require 2x10 inch passive intakes.

I remember seeing a video, years ago. The point of the video was to determine what amount of passive inlet space was the most efficient when used in conjunction with an exhaust fan. They took a "room" and filled it with smoke, then experimented with various combinations of sizes of fans and number of equal sized passive inlet ports. The object was to see which combination cleared the smoke out the quickest. The winner was a 5-to-1 ratio. Whatever sized fan was used, five (equal sized) inlet ports were the most efficient. Less than five and it just took a lot longer to clear the smoke, more than five didn't really help that much.

So, to answer the O.P.'s question, you want 250 square inches of passive inlet space.