# Are computer fans strong enough to pull through a small carbon filter?



## praiseodin (Jan 16, 2013)

hey guys, ive been having doubts lately about whether a 120mm PC fan is strong enough to pull through a DIY carbon filter. Do you guys use any special kind of fans for that, does it need to be at a certain speed to be able to pull through the filter?
In my cab thats in my signature i was wondering if one PC fan would be enough to extract all the smell from the cab through a filter or if i should make two filters with 2 fans to keep the smell at bay?

Thank you for your help guys! Much appreciated


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## Nice Ol Bud (Jan 16, 2013)

Lol hell no


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## Nice Ol Bud (Jan 16, 2013)

your going to atleast need a squirrle cage fan. I perfer inlines though.


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## praiseodin (Jan 16, 2013)

I'm trying to make the cabinet as quiet as possible that's why I'm avoiding any big intake fans and i wasn't to eliminate the smell as well
Any other options to keep it quiet while removing the smell of two plants?


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## praiseodin (Jan 16, 2013)

This fan has a decent CFM, they claim 150cfm 

http://www.pccasegear.com/index.php?main_page=product_info&cPath=9_601&products_id=19129

Or this they claim 170cfm at 2000rpm
http://www.pccasegear.com/index.php?main_page=product_info&cPath=9_601&products_id=22027


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## gagekko (Jan 16, 2013)

praiseodin said:


> This fan has a decent CFM, they claim 150cfm
> 
> http://www.pccasegear.com/index.php?main_page=product_info&cPath=9_601&products_id=19129
> 
> ...


Those are free flowing ratings - doesn't really do anything for obstructed flows.


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## praiseodin (Jan 16, 2013)

In a small cabinet that is roughly 3x3x2 = 18 cubic feet would that fan be adequate even tho it would have to pull through a carbon filter.
Say if the filter obstructed it by %50 then the air flow would go from 150cfm to 75cfm, then divide how many cubic feet my box is, which is 18.
That would equal the fan cleaning out the cabinet at 4.1 times a minute.
Unless I'm wrong with my understanding of how it all works :/


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## Darkjasper (Jan 16, 2013)

I personally (with the little experience i have =P) would think that the fan would not pull air enough through the filter. I have a 200mm 165cfm fan as a exhaust (will be a intake fan when I get my tent) and if any thing is near the front of it it slows the pull down drastically. Almost to the point that there is not any air flow. 

You also have to look for the filters cfm rating. I have not seen any filters with below a 100 cfm rating on it =(. Maybe a couple of ona blocks would be up your ally?


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## praiseodin (Jan 16, 2013)

On a block sounds good as well but i was actually thinking of making a carbon filter like this

https://www.rollitup.org/do-yourself/101248-best-diy-ez-walmart-carbon.html

I only need a small one for my cabinet, that's why i am curious if a PC fan would do a good enough job of pulling through it 
I don't imagine the cfm needed to pull through that filter would be too high


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## Darkjasper (Jan 16, 2013)

You could try it, seems pretty cheap to make. Look for some cheaper fans though. No reason to spend 40 bucks on one. Though remember that that pencil holder is way smaller thant a 200~ mm fan.


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## praiseodin (Jan 16, 2013)

I can always get an adapter made up result enough to connect the fan to a small filter
Im just wondering if that filter and fan would work to take out the air fast enough to keep temps nice and also reduce the smell
I'm still undecided about a 250w or 400w in my 3x3x2 grow space
So i need to move as much air as i can while still keeling silent


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## mr2shim (Jan 16, 2013)

Computer fans rated cfm is with absolutely no resistance. You put a filter over it or in it's way the rated cfm plummets to about 0. They are by far the worst fan you can use. Get an inline duct fan. They are much better, although they are far from the best it will do a hell of a lot more than a stupid computer fan.

If you're going to get a 250 or 400w hps/mh don't be an idiot. Get an inline fan.


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## exabits (Jan 16, 2013)

If you are set on using a computer fan and need some serious cfm, get a delta. Recommend http://www.frozencpu.com/products/8147/fan-500/Delta_Mega_Fast_120mm_x_38mm_Fan_-_252_CFM_-_Bare_Lead_PFB1212UHE-F00.html?tl=g36c15s562, serious fans, these will remove fingers.


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## mr2shim (Jan 16, 2013)

exabits said:


> If you are set on using a computer fan and need some serious cfm, get a delta. Recommend http://www.frozencpu.com/products/8147/fan-500/Delta_Mega_Fast_120mm_x_38mm_Fan_-_252_CFM_-_Bare_Lead_PFB1212UHE-F00.html?tl=g36c15s562, serious fans, these will remove fingers.


I had one, tried it. Made a homemade filter and after putting that on the cfm was basically zero. They don't have the torque to flow air with resistance from a carbon filter.

inline duct fans are cheaper and better.

BTW, those fans are loud as fuck. Sounds like a damn jet is in your house.


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## exabits (Jan 16, 2013)

You are entitled to your opinion. I agree that inline duct fans are superior and better suited to the task. Though I also, disagree, a couple of these deltas will suck through a carbon filter with ease. At over 500cfm, these fans are no joke when running at 7k rpm. Meant for "sucking" air through radiators, these fans have the power whether yours did or not.


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## mr2shim (Jan 16, 2013)

exabits said:


> You are entitled to your opinion. I agree that inline duct fans are superior and better suited to the task. Though I also, disagree, a couple of these deltas will suck through a carbon filter with ease. At over 500cfm, these fans are no joke when running at 7k rpm. Meant for "sucking" air through radiators, these fans have the power whether yours did or not.


You can look at my first grow if you like. It's on this site, I had two of them. They were a different name but had the same rated cfm. With both of them on they were insanely loud. The OP already stated that noise is an issue. Those fans are loud. Have you actually used them?


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## AegisVeritas (Jan 16, 2013)

You should get yourself an inline fan and insulate the housing to reduce sound. There is this material used for car stereo and road noise dampening called, Dynamat. Its easy to use and works very well for reducing noise. Its easy to use, just remove the backing and place it on like a really thick sticker. You can pick it up at auto zone, pep boys, etc. Then you'll have plenty of cfm and low noise.


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## ASMALLVOICE (Jan 16, 2013)

I use a 120cfm 6" axial fan (67,000hr life) through about 10 feet total of ducting and light and it is cool to the touch even with 73 degree air at the intake and almost silent on "duct" noise (6" duct can only handle so many cfm before it starts to whistle) but it will not do squat on a carbon filter( probably burn out fairly quickly).

There are axial fans out there that do have the capacity for pulling through a small filter, but to do it efficiently and not make it sound like a 3 foot dremel tool, a centrifugal(vortex) fan will stir the koolaid much better. I have a 4" on a 14" filter in a 4x4x7 room and it works without a hitch.

Peace and Stealthy Grows

Asmallvoice


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## exabits (Jan 16, 2013)

You can look at the data specs, http://www.delta.com.tw/product/cp/dcfans/download/pdf/PFB/PFB120x120x38mm.pdf , I know how much air it moves, I know the air pressure it can exert and I know how loud it gets. Are you out to be mrThreadwarrior? If I get banned for this post, I don't really care, look at my post count... You said your own fail. Delta is the only company that makes a pc fan that powerful. If you didn't have a delta then your fans were shit, it's that simple. I don't know how many decibels a 4" inline is but I know my 6" is roughly the same a delta. Sound can be dampened and reduced. How many people here have sound reducing techniques? You keep argueing your opinion about your fans.....until you own a Delta UHE you shouldn't even comment about how your fans couldn't hack it and no other pc fan can either. It's simple science, this delta http://www.frozencpu.com/products/81...?tl=g36c15s562 fan moves more air then a 4" inline such as http://www.htgsupply.com/Product-Inline-%204in-Fan-by-CAN.asp


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## exabits (Jan 16, 2013)

Anyway, I was just trying to help the guy out, as I know more about pc parts then others, I was offering my expertise. I agree still that a AC powered inline fan is superior in general but this guy was set on a pc fan so I was "giving" him an option. If this was for some stealth speaker box grow and I'm trying to cool a 400w light, delta would be the way to go.  If your running a carbon filter and possibly air cooled light, don't scimp, get a proper inline duct fan!!


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## mr2shim (Jan 16, 2013)

exabits said:


> You can look at the data specs, http://www.delta.com.tw/product/cp/dcfans/download/pdf/PFB/PFB120x120x38mm.pdf , I know how much air it moves, I know the air pressure it can exert and I know how loud it gets. Are you out to be mrThreadwarrior? If I get banned for this post, I don't really care, look at my post count... You said your own fail. Delta is the only company that makes a pc fan that powerful. If you didn't have a delta then your fans were shit, it's that simple. I don't know how many decibels a 4" inline is but I know my 6" is roughly the same a delta. Sound can be dampened and reduced. How many people here have sound reducing techniques? You keep argueing your opinion about your fans.....until you own a Delta UHE you shouldn't even comment about how your fans couldn't hack it and no other pc fan can either. It's simple science, this delta http://www.frozencpu.com/products/81...?tl=g36c15s562 fan moves more air then a 4" inline such as http://www.htgsupply.com/Product-Inline-%204in-Fan-by-CAN.asp


Have you used one? Pictures of your setup?


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## exabits (Jan 16, 2013)

Sure, why not... Here is 3 150cfm deltas pulling air through a xspc 360 radiator for my water cooling in a corsair 800d pc case.


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## mr2shim (Jan 16, 2013)

So because they pull through a radiator you think a carbon filter is the same thing? Ok, this is when I stop discussing this with you.

What kinda cpu are you running to need water cooled?


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## exabits (Jan 16, 2013)

Theres no need to debate this anymore. Go read the pressure specs, the guy can make his own educated decision.


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## RoYalQuEenChEeSe (Jan 16, 2013)

OP get a proper fan dont mess about with pc fans. wireing pc fans to chargers is asking for a fire chargers get hot left on continuous im speeking from experience.


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## praiseodin (Jan 16, 2013)

to be honest, im looking for a decent priced option to pull air through a small filter that ill make and will be quiet as the cabinet may go into either my computer room or garage. both options it needs to be as quiet as possible to reduce suspicion


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## RoYalQuEenChEeSe (Jan 17, 2013)

praiseodin said:


> to be honest, im looking for a decent priced option to pull air through a small filter that ill make and will be quiet as the cabinet may go into either my computer room or garage. both options it needs to be as quiet as possible to reduce suspicion


4" RVK and fan speed controller = peace and quiet
And if you decided to go a bit bigger you have a good fan to start with.....


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## exabits (Jan 17, 2013)

I recommend the pc fans, only because this is a stealth grow with very limited space. Sticking a 4" inline in your grow cabinet doesn't really even seem like a option to me. If it were me I would get 4 delta's and run a 4 into 1 for the purpose of reducing the fan speed. As I'm sure these delta fans get louder then a 4", you do not want to run these at full throttle. If you run 4 at 50% or less, that is a very viable option for you and can move far more air then a 4" or even 6" inline fan, speed dependent.


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## OGEvilgenius (Jan 17, 2013)

praiseodin said:


> In a small cabinet that is roughly 3x3x2 = 18 cubic feet would that fan be adequate even tho it would have to pull through a carbon filter.
> Say if the filter obstructed it by %50 then the air flow would go from 150cfm to 75cfm, then divide how many cubic feet my box is, which is 18.
> That would equal the fan cleaning out the cabinet at 4.1 times a minute.
> Unless I'm wrong with my understanding of how it all works :/


Air movement is a function of RPMs and fan size more or less assuming no resistance. So you can get away with a small motor with little power to deal with a resistance free situation. 

It's also why more powerful fans don't necessarily move more air when rated unobstructed. 

CFMs here are largely irrelevant if the motor you're using doesn't have any oomph.

CPU fans have no oomph.

I had a relatively powerful axial fan which is built somewhat similarly to a computer fan only a lot more powerful that was fairly quiet (if mounted right) and was acceptable to push air through a small carbon filter (sub 200 cfm).


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## exabits (Jan 17, 2013)

I love how each person with no experience with these delta fans has a notion to prove that the world is flat. Should we turn this into a does LED lights work or maybe some other about how it only works if 99% of the public agrees.


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## mr2shim (Jan 17, 2013)

exabits said:


> I love how each person with no experience with these delta fans has a notion to prove that the world is flat. Should we turn this into a does LED lights work or maybe some other about how it only works if 99% of the public agrees.


Shut up about your stupid fucking loud ass pc fans. They're loud as fuck. Can you not read? Jesus... You are under the retarded idea that having 2 250cfm fans gives you 500 cfm. Tell me how this is possible.

If you honestly think you can take a silly little pc fan and compare it to a 4" inline fan and think the cfm will not drop on the pc fan when you add a carbon filter you are an absolute fool.

Do you even grow? Let's see something. Because all I've seen is you post a picture of your computer. We all have one of those buddy.



praiseodin said:


> to be honest, im looking for a decent priced option to pull air through a small filter that ill make and will be quiet as the cabinet may go into either my computer room or garage. both options it needs to be as quiet as possible to reduce suspicion


http://www.lowes.com/pd_234523-1061-DB204_0__

Don't listen to that moron going on about PC fans. Take it from people who have used them before. They are shit, they are designed to flow the rated cfm with absolutely no resistance. With the resistance from a carbon filter they will move about 0 cfm.

Even the "glorious" delta pc fan. It's still a pc fan, it still uses a micro dc motor that has no torque. If you can stop it from spinning with a stick, it's not worth anything.


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## exabits (Jan 17, 2013)

Sure, I guess I'll bite. Just because I don't have 3k posts doesn't make me a retard or inexperienced. For the sake of proof I guess I will shit on this guys thread because mrForumwarrior has a beaf with pc fans and me. I suppose your a guy that would say you can't use a window a/c as a water chiller, just as you can't use a fan to do a fans job. Just because it isn't the norm, doesn't make it wrong, apparently many people here could learn a lot from that statement. Here's a few from 2 past grows around 09' and proof I do know what I'm talking about, some would call that intelligent. 

Edit: Little ghetto back then...well I've since moved on to bigger and better things, more watts and more pots. Thread Op, believe what you want, I can't fight a whole forum of ill informed neighsayers. I'm sorry to derail your thread because people can't deal with a fan that's different then the norm.


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## br3ttiboy (Jan 17, 2013)

i personally wouldnt risk trying it on my plants lol but if its just noise you're worried about, id recoment using a quality extractor fan with a silencer, keep ducting as short as possible with minimal bends and insulated if affordable, also fileing small v shaped grooves along the entire length of the back edge of the fan blades will DRAMATICALLY reduce noise, hell iv got a 5 an a 6 inch fan running in my bedroom an i sleep soundly lol. i really wouldnt recomend doing what you're doing as air flow is important, you dont want it stagnating in there, if you do try it let us know how it goes! lol good luck


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## mfkl90 (Feb 25, 2013)

mr2shim said:


> Don't listen to that moron going on about PC fans. Take it from people who have used them before. They are shit, they are designed to flow the rated cfm with absolutely no resistance. With the resistance from a carbon filter they will move about 0 cfm.



not... strictly true. 
i have a stealth grow going with a pc 120mm fan pulling through a small yet effective custom built carbon filter. temp in grow room DROPPED, indicating air movement. and when you put ur hand up to the filter you can feel air being drawn. activated carbon layer does not have to be big for 3 or 4 plants, any more then you need real deal I AGREE! providing the air passes over and around the carbon, it stops a big majority of the smell, maybe not as effective as other options, but it does work.
i also have an inlet air duct which has no fan running, i'm not even kidding. the air up in the loft pushes through down into the room anyway (i can always feel the draft) so there is an adequate intake and extraction.

pc fans DO work, even with a small makeshift thin layered carbon filter. i wouldn't go any lower than 120mm fan size tho, that probably would be crap. hell if your not worried about the smell going out, then thats sufficient either way.

fan fire risk, yer.... can agree for most part. but then, the whole part about growing is a fire risk, lol.


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## P0V (Feb 27, 2013)

if you keep pumping air into a large room with a small fan the large room will hold more air pressure in it then what the small fan did have in the first place ? let the room pressure push air through the filter instead of the fan pressure..


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## mrueeda (Feb 28, 2013)

Im engineer and still remember something on my exam on the sizing of idraulic networks...Basically working with the airflow is the same exact thing...The carbon scrubber is simply seen as a resistence in the circuit (and every filter has a different value in base of its constructive properties)...What you really want to look at when choosing a pump or a fan in this case is the PRESSURE DROP that it is able to create...because only this value will be able to tell u how many cfm will be able to pass through the filter...Consider for analogy an electric circuit in which we will have that the CFM (airflow A) that will pass through the resistence (R) of the filter will be given by A=P/R where P si the pressure drop that the fan is able to generate... 
 
So...what does this stuff mean ? We never know the resistence of the filter.. so we cannot solve mathematically the problem...but this just helps us to comprhend which is the true spec that we want to search...It all comes to what airflow we want to pass through the filter...and it is determined by the static pressure that the fan is able to create and just by that...
So coming to the fans...without a doubt inline fans are the best choice but if a pc fan is able to drop enough static pressure i dont really see why it shouldnt do the task...The pressure in general is related to the torque delivered by the fan and it is more or less proportional to the amperes sucked by the motor...On the market there are very diversified fans and some of that (Delta for example) work with much higher courrents (4-5 Ampere) than most of the pc fans available and giving as output high levels of static pressure which are able to push even through a carbon filter...That said it is certainly not the best choice..


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## Zippo Guy (Mar 14, 2013)

depending on size of grow space, the only ones that might come close are going to cost you about the same as typical fan as you may end up needing more than one (but hi-spec PC fans are far less noisy than cheap ruck competitors ect.).

also, the best option in my opinion is to blow through a carbon filter (as fans are most efficient at sucking around the edges), this allows the filter to build up air pressure inside it, and extend it's life by utilizing all of the carbons surface area.
I dont want to get into a suck or blow war lol... this is just my opinion, also based on the general idea that it's best to oversize your ducts, fans and filters.

All this being said, if your space isn't that big and PC fans are your best option, you will definitely be better off blowing through a filter.
Remember, when thinking of PC fans check the pressure rating (can't remember correct term at the mo...), not just the cfm. All PC fans are good at blowing, few are good at sucking... check the brand "Noctua".

Zip


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## mikbull (Nov 8, 2015)

This is an old post, however, one of these:. http://www.amazon.ca/Bgears-b-Blaster-90mm-Bearing-Extreme/dp/B0043GQJ5M will work through a: https://www.rollitup.org/t/the-best-diy-ez-walmart-carbon-filter-for-micro-grows-zen-style.101248/ . Make sure the fan pushes through it as the PC fans aren't designed for pulling. If you wish to test, just tape a plastic garbage page post filter on the exhaust and watch it fill up. Fan on inside of box filter taped to outside.


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## PicklesRus (Dec 18, 2015)

praiseodin said:


> hey guys, ive been having doubts lately about whether a 120mm PC fan is strong enough to pull through a DIY carbon filter. Do you guys use any special kind of fans for that, does it need to be at a certain speed to be able to pull through the filter?
> In my cab thats in my signature i was wondering if one PC fan would be enough to extract all the smell from the cab through a filter or if i should make two filters with 2 fans to keep the smell at bay?
> 
> Thank you for your help guys! Much appreciated


Bc northern lights grow boxes uses the same style fans as PC fans but they are a lot beefier, my local hydro store sells them, they look like a normal PC fan but a lot more rugged and I believe they accept 110v. That's what I'm planning on using on a small carbon filter for my micro grow


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