grow tent exhaust and intake 6inch and 4inch

i have a 600hps in a 5x5x7 grow tent. i have a 6inch and 4inch vortex fans. i have both hepa filter sizes as well. which should i use for intake and exhaust and why? muchly appreciated

You always want the larger fan exhausting the hot air out and the smaller fan bringing in the fresh air. This is so that there is negative air pressure in the tent and no nasty odors will sneak out anywhere, the only air leaving the tent goes through your fan and odor control system.

if your exhaust is 4 inch then you want the intake bigger, search the forums its explained better i researched this for a couple days

amrcngror how do you figure you want the intake to be bigger than exhaust? As choc said, the opposite is true so as to create a vacuum inside the box, which is what you want. Most people don't even use intake fans (myself included, with 6inch 440cfm exhaust).

amrcngror said:

if your exhaust is 4 inch then you want the intake bigger, search the forums its explained better i researched this for a couple days

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ah he is somewhat right but a little confused. only when using a PASSIVE intake then you need the intake to be larger than the exhaust to relieve pressure. but if you have an active intake (powered by a fan) then it should be a weaker (smaller) fan than your exhaust so you maintain negative pressure and control the odors. i hope this clarifies things for you all.

Your intake size should be 25% larger then your outtake size. There will be no intake fan required this way. The 25% increase will compensate for the static pressure drop on the induced draft side of the fan, meaning you fan will run much more efficient.
If one was dealing with a high static environment (ducts or openings are too small for fan) 2 fans with the same specs should be used, the second fans (intake fan) main purpose is to ease the static resistance of the first fan. If the intake fan was smaller in size all it would do is create static resistance on the primary fan, thereby reducing efficiency of the fan.

Kind