Advice on Passive intake for mini-grow

6 inch is better, and with passive intake there is nothing to think about, the whole idea with passive is so the extract fan sucks air from all directions including leaks

 

Just food for thought:  carbon filters need the proper size fan (in cfm's) to operate effectivly and a little inline may not do the trick.  I wouldn't think a micro grow needs much either.   

 

A 4 inch inline fan/carbon filter combo is enough for your small box.

 

I agree, 4".  Anything larger is overkill.  Do a google on carbon filter fan combo's.  If nothin else, you'll walk away educated.
If not, make your own out of a coffee can and some real dirty socks.  Kidding, but it's an idea.  GL with your grow      

 

 
Completely disagree. 6" is tremendously better than 4". a 4"fan at full speed pulls ~140cfm. A 6" at full speed pulls ~400cfm. I know from experience, a 6" fan running at 1/2 speed is tremendously quieter than a 4" fan at full speed. PLUS, if it gets hot you have the ability to turn the fan speed up. Also, if you have proper ventilation, not just filtering, you can reduce smell as well. My grow area completely ventilated about 20-40 times a minute. Because of this I NEVER had any smell in my closet,.... again, closet. When I turned my fan off and got ready to chop, the smell  went from nothing to HOLY SHIT THAT SMELLS LIKE WEED in about 1 minute. Oh, and I didn't have any filter on this exhaust, I relied purely on extreme circulation. Bigger is better in this situation.
 
EDIT: Sorry, misread the dimensions as inches instead of centimeters. Yea, a 6" fan would be overkill.

 

I'm going through exact same thing atm, my closet is slightly bigger but I'm using LED's. I was worried a 6 inch will circulate too much and make it too cold all the time.

The 4 inch fan I'm looking at was 190cfm. Cherokee has me thinking now about noise again too, I thought a 4 inch would be quieter then a 6?

Would using alloy or PVC pipe be quieter then aluminum ducting?

 

You should use a metric fan to vent a metric space. Instead of a 4" I would suggest a 10.160cm fan
 
Just sayin'

 

What difference does it make lol.

Roughly 3x1x6 if that helps?

 

It is counter-intuitive. The way fluids work, and air is a fluid, when you increase the cross-sectional area of the fan the efficiency increases exponentially. That's why a 6 inch fan can move more than twice the air of a 4inch fan. And because the fan can move so much more air you can turn it down to a lower speed which in turn makes it much quieter. Using a larger venting system reduces friction loss against the sides of the ducting as well

 

  Wow, you must be real confused by now.  Like I said, do a google on fan&charcoal filters.  Only you know your circumstances, so only you will finally decide.  Regardless, an exhaust fan is absolutly necessary for sufficient air circulation.  I never asked where you would exhaust the stale air to - ie. back into the room or outside?  I see micro growers using computer fans all the time, but just for air flow, no filter attached.  Also look into inline booster or duct fans, $25 on line.  Idealy, if your not worried about the odor outside the house then skip the filter and just use an exhaust to the outside, inline booster is perfect for that.  About the odor, your gonna get it everytime you open up your grow, there's no way around it.  Odor jells in a can that you just place in your grow op will also help to an extent.  But all in all, you're the boss and it's your call.  Good luck man
Sky           Sorry for the book    

 

 
 
Ok mate you seem to know what's going on so how about this one. Could I split a carbon filter between two different rooms (shared wall) each with there own passive intakes? Or would it just suck through the closet one? AND..
 
Would the rooms still be independently light proof?
 
I've been dying to ask that question for a while haha.

 

I have seen this done before on Youtube.  Without seeing your set-up or getting all scientific about this, it sounds doable to me.  I'd recommend putting the exhaust fan in the flowering side where most of the odor is.  The proof is in the pudding - try it and see how it works.  You can always change it.  GL

 

 
I think if you want to use 1 fan for both rooms you could do a few different things. You can have 1 room with a passive intake, then a vent between the 2 rooms, then the fan/filter venting out the second room. Or you could run ducting from each room to a T-connector and then the fan so it would be pulling pretty equally from each side. Be aware though, like I said before about friction loss. If you have 1 room with 20' of ducting to the fan, and the other room with only 5' before the fan, it will pull more from the second room because the 5' section will have less resistance, although unless you're talking about extreme differences in length, it should be negligible.
 
The lightproofing would be hard to advise without knowing exactly what you plan on doing with the 2 rooms or how it is constructed. Regardless of how you vent, lightproofing will have to be something extra to think about.

 

Yeah sorry I should of been more specific. It will end up basically being two cupboards pushed together, Veg on the left and flower on the right. Needs to look completely normal from the outside which is the reason for the carbon filter being shared and hidden between the two adjacent walls (to save on costs too). Ducting will exit flower room. Will have passive intake from outside (want CO2 eventually but to much hassle atm) and vent outside.
 
I had a feeling the light proofing will be hit or miss, I guess I just have to work it out if/when it becomes an issue.
 
Thanks for the feedback blades.

 

 
Technically, the filter doesn't need to be shared between the rooms. You really only need it on the flower side. Sure a plant in veg has an odor, but its very minimal and isn't anything that's distinctive, just smells like leaves do. Depending on how handy you are at carpentry, I would try something like this...
 
First off, I'm assuming, like you said, it is two separate cupboards. Get some wood that matches (close enough) to what the cupboards are made of. Set the two cupboards 4-6 inches apart from each other and construct a "belt" that will go around and connect the cupboards together. You may or may not want a PC fan in the back of this cavity as well to vent out excess heat, depending on what kind of lights you will be running. I would also put a hinge on the back piece so you can access the central area. From the left box, veg, vent with an elbow shape into the cavity pointing down. Then route with aluminum duct fittings and elbows to the bottom of the cavity and into the flower room. Note, the more bends in the cavity the more time the air in the ducting will have to cool off prior to entering the flower room. Then, out of the top of the flower box, put another elbow point horizontally and backward into the cavity as high as possible. After this elbow, install your filter and exhaust fan blowing out the back of the cavity just above the first PC fan I mentioned if you installed that one as well.

 

I'm painting the inside of one of the cupboards at the moment, I'll post up a pic when it's finished.