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Carbon filters, Better to push air through, or draw from?

Discussion in 'Indoor Marijuana Growing' started by MDxx, Feb 10, 2010.

  1. Ill be building a can style, 1 gallon activated carbon filter for a small space. I'm curious if the filter would be more effective drawing air from the filter or forcing it through. Seems they would both give about the same surface area but i have no experience with carbon scrubbers yet and would like to hear from those who may have made a filter in the past and how effective it is for their area. Thanks in advance
  2. carbon filters are specifically made for sucking air through (in). simply attach a fan and some ducting and have all the bad air exhausted from your room. i'd also recommend a fan to bring in fresh air. then your giving your room optimal air circulation :)
    hoped i help
    good growing and much luck
  3. I have seen a few threads where a person has recommended that the carbon filter be reversed and have the air 'pushed' through it. This would not work properly if you are venting to the outside. Unless you put your filter outside as well. It really doesn't matter if you have an inline fan. The one I have is 6" @ 430cfm. That is fucking strong man! Most bathroom ventilation fans are 70 - 90 cfm. <- these are crap though and I wouldn't ever install one.
  4. I would say that you should "push" the air through the carbon filter.. however, either way will work.

    <==== carbon filter <== inline fan <==== grow room <==== inline fan<===== fresh air

    The "===" is the ducting and the "<" is the direction air is flowing

    The reasoning behind the way I do it this way is to create more momentum in air flow before it reaches the filter from the fan. When the air is pushed through rather than drawn my DIY carbon filters tend to last longer than if put in front of the fan. Do remember you want your room air-sealed as much as possible if you wish for your filter to really help with odor.

    your friend hiesman.
  5. #5 Martano666, Feb 10, 2010
    Last edited by a moderator: Feb 10, 2010

    This is NOT how the filters are designed to work. Also, this way you are going to have all the heat build up in your house, and it looks like you have 2 fans running. This is NOT very efficient, and in the summer, your AC will be running non-stop because your house will be hot. So that way you will have not only 2 fans running, but they are also not getting rid of the heat in your house and therefore, causing AC to use even MORE energy. The proper way is:

    Carbon filter==> Cool Tube Light ==> Inline Fan ===>vented outside through exterior wall vent.

    This is the MOST efficient way of using ventilation. This way uses stale air from in your house. The filter should be located IN the grow room. Air is drawn from outside of your grow room, in to the room and up in through the filter, which is used to cool the light and ejected outside.

    You do NOT want your room air-sealed. Why do you think the grow tents come with little air vents? The very fact that you have ductwork venting in to your room means it is NOT air sealed. The goal is to get as MUCH heat, and ODOUR flowing outside of your house as possible. If it is winter, you can unhook the external vent, and let the heat flow in to your house if you want to, but, in the summer, that is not going to work at all.
  6. Appreciate all the replies! both ways seem legible seems to be a toss up. Should have mentioned i already have a small intake (about 1 inch tube) with a PC fan to bring in fresh air however this pushes out much of the stinky stale air through the door cracks and such so a filter is a must. I do have a flow hood for my HPS so i think ill go:

    Hps hood====>Fan(pushing air) =====> Carbon filter ====> exhaust

    I've also heard that passing the air at a slower rate (60-100 cfm) gives for a better surface area to scrub the air. This would make sense curious if anyone has had problems with a high flow fan pusing air at a high rate maybe letting smells escape? any input is welcomed

  7. agree 100%, if you push air into a carbon filter it will create positive pressure and your fan motor will not work at full capacity and good chances air leaks might happen and thats when the smell gets out
  8. i dont know about homemade scrubbers, but the ones you buy are cfm rated and on avrg you want to go with a fan thats half that, ex: filter has 2500cfm rating, go with 1200-1600cfm fan, otherwise the air dont get filtered as well and you risk sucking the charcoal out ruining the whole process
  9. I think if you did it like this the air would come out of the carbon filter and not even make it to the exhaust that you have past the filter. My can filter only has a hole in one end to connect to a fan or vent of some sort. When your fan pushes air into the filter isnt that air going to escape out the sides of the can and not even go to the exhaust. And if your filter has a hole in both ends then i would think the air being pushed from the fan would go right by all the charcoal without being scrubbed through it, making your filter useless.
  10. EXACTLY!

    Maybe I am wrong, but all of the carbon filters that I have ever seen, are designed to connect to the END of a length of ductwork. I have never seen one that can be installed in the MIDDLE of ductwork. You can only hook duct up to one end of the can, and the air is pulled in through the sides of the can filter. \

    If you 'pull' air through the filter (the proper way it is meant to be used) the canister can sit right in your grow room. This will create a negative pressure in your grow room, and NO ODOUR will leak outside of it. Air can only flow INTO the room by going through a crack, or a vent of some sort, and air can only flow OUT of the room, by going THROUGH the filter, and outside through the exterior wall of your house. (cooling your light in the process)

  11. Listen dude. You don't need that PC fan anymore if you are seriously hooking up a decent inline fan. Your problem with the stinky air getting our of the room is because of your setup.

    #1 RULE: You need negative air pressure in your grow room. By using a PC fan to push air into the room, you are doing just the opposite. You are creating a positive pressure in your grow room and thus, forcing some air out of the room (somewhere).

    If you hook your filter system up the way I said, you can toss out the PC fan and you will have NO PROBS at all. If you are hooking up a filter in the middle of the ductwork (like you described) you are doing it incorrectly. I don't understand how your filter will work. If you built the thing yourself you might not have done it correctly or maybe you have some different sort of filter design that I haven't seen before.

    Anyhow, good luck. I hope you listen to me.:D

  12. What kind of design did you use to make your filter??? You can hook a duct up to BOTH ends of your canister???
  13. hey buddy... ease your mind, smoke one. Its obvious your a "grow tent" kind of guy, LOL. I'm more of a 300 plants at once kind of guy aka a room not a tent (but that doesn't matter. this is about pushing or pulling through a carbon filter, which is better?). I use two powerful fans... one pushing fresh air into the room and one sucking air out. Its obvious that the air that is going to be pushed out of the room needs to be treated for odor. Having your room air tight means there are no air leaks, repeat after me... LEAKS.

    lets look up what leak means. Leak- the entrance or escape of a fluid (in our case air) through a crack or fissure.

    ok. so a leak is a place where there is a crack or fissure. If there is any part of your room where air can escape without first being treated by a carbon filter, then you are defeating the purpose of having a carbon filter. Which seems obvious to me is for odor control. If the air your pushing out of the room isn't treated then its gonna be that skunky smell of a flowering plant, which can linger into the wrong persons nose and cause security problems. What mr. angry post said about having a carbon filter in the room can be done. This is to keep the smell of your operation less skunky but when you have say more than 20 plants flowering your efforts are in vain (not saying it can't be done, just not what I do) Having one to filter exiting air works great in my opinion.

    let me sum this up so the guy with maybe 10 plants (if that) in a grow tent with maybe 4 harvests under his belt will get it...

    Source of fresh air => fan>==> grow room that is sealed == fan>==>carbon filter====> away from grow room outside.

    Proper venting is necessary for more than just temp control or odor control, maybe this is the case for our angry poster ( i say angry because the all caps says to me that you are yelling or frustrated while trying to prove a point) , but to everyone else who is growing, proper ventilation is to provide our plants with fresh air that contains CO2 which is a piece of the puzzle that is photosynthesis. Sure the constant change of air will help with temperature control and venting through carbon filters will help with odor, but the most important part is providing our girls with what they need to grow. It is all a delicate dance that will take fine tuning.

    As far as your first paragraph that makes little sense, I did state that I use a carbon filter that is DIY as in do it yourself, as in I MADE IT. Who are you to say how a carbon filter is designed to work? Especially the one that I use. Also, I said in my post, hey this is my suggestion, but either way will work. I guess you missed that. As far as my house being hot because I have two fans running seems a little pardoxical, fans are used to cool, and your logic of "over heating" is nonsense.

    To reanswer the original question which was which way will work, pushing or pulling air through a carbon filter? Not "what is the most efficient way to try to prove someone wrong and tell how you duct your grow tent, which must be the right way and anyone who has something different is a complete noob and doesn't know how to grow and will have a hot house and a high AC bill because they have two fans running non-stop (i still don't get that how you came to that conclusion) and flat-out totally miss what "air-sealing" your room means"

    I would say that if you PUSH air through a carbon filter your better off because....

    dun dun dun dunnn da dunnnnn

    your fan and carbon filter will last longer

    who you gonna trust? mr. grow tent the angry poster

    or... your friend Hiesman the ten year veteran.
  14. Either way works and they're are pros and cons to both approaches. Sucking is easier on the fan, especially if you have a wimpy fan, but blowing into a filter is a more efficient use of the carbon.

    Air being sucked into a pipe comes mostly from the sides. So, sucking through a filter brings air mostly just through the carbon that is closest to the duct intake. Blowing into a filter 'pressurizes' it forcing air through all of the carbon. Also, a carbon filter downstream of the fan makes a nice muffler. You'll need a more powerful fan to blow through a filter - not a wimpy duct booster.
    zeroz52 and HydroGrowz like this.
  15. This is the best approach to the question. short simple and to the point + rep man.

    whatsup johnk you smokin good?
  16. In a month I will be... :D

  17. ???????

    I apologize if you think I sounded angry. I just re-read my message and I think you are right. That is not the way I should be coming across in a marijuana related forum. We're all tokers aren't we?! You mentioned that you think I sound angry because I used so much caps in my message. Well, go count, you will see that you used the same amount of caps. I guess you are angry too? lol. I didn't mean to come across like a dick head. BTW I did go smoke one anyway!!

    Now, the dude that was asking the question is only doing a tiny little grow. AND, yes, you are correct, currently I have a grow tent setup. So, the scale level that I grow at, is much closer to the scale of grow that MDXX is going to be doing, so why would I be unqualified to answer this question? We were talking about airflow, not growing. I've worked in residential construction for years, and probably know more than you realize about furnaces HRVC, HVAC, and other ventilation systems.

    If you have 10 years of growing experience, then you are definately FAR MORE experienced than I am in growing and I won't even debate that, but I don't think you explained yourself very well. (I'm not angry, but I know..... I used caps, lol)

    There has been atleast 2 times that I have encountered someone who made a DIY carbon filter, by following some 'online instructions' and totally fucked it up so that it was useless, but didn't know it. The design was a canister type filter (the only type I've seen in grows) like I described before, that hooks a duct up to one end, and the other end is capped off. Air is to be drawn IN through the sides. Well, the dude that made the filter, didn't know this, and never capped off the one end of the filter. They thought that air passing THROUGH (end to end) the canister was how it was meant to work. Well, you and I both know, that aint gonna work. Air has to pass through the carbon. I was concerned that MDXX was going to do the same thing as the dude I was talking to before.

    Fans don't cool air BTW. Not one BIT. Not to mention that fans actually generate heat and slightly warm the air that pass through it. A fan can move air from one point to another, but is useless in LOWERING air temperatures. The only way temps are kept down, is by using the fan to actually REMOVE the air. You know this, yet you didn't explain. If you don't vent the air outside of your house, then you are going to have heat buildup. Sure, the heat will disperse, but if you are in a smaller house/apartment, you will have major issues in the summer. You don't need to draw CO2 from outside of your house. As long as you draw it from out side the grow room you will be fine. All I am saying is that in a small grow room (not 3000000 plants, like you have) you don't need anymore than one fan to REMOVE air, and filter it in the process and also cool your light in the process. This is the most efficient way of using 1 fan. Then, quite automatically, your grow room will DRAW air from the rest of your house (without a fan PUSHING it in there). However, if you still insist on using 2 fans, then the fan that is removing air from your room, MUST be stronger, than the one that is pushing air in to the room. Again, this goes towards creating a negative pressure in the room.

    HIESMAN If you disagree with this setup, you should exlain why. Also, in your diagram, you didn't even put a picture of MDXX's light hooked in to the ductwork. He said he has a coolable reflector yet you didn't mention it in your expert advice. Why shouldn't he hook the duct up to his HPS HOOD? Don't you want to remove that air...or is the fans gonna cool the air all on it's own like you said fans do?
    Remember, we are trying to give advice that is relevant to the guy ASKING the question. We aren't trying to showcase how many years of experience you have, or how many plants you grow at once.

    Anyhow, my apologies again. I don't want you to think I am a dickhead cuz I am not. My message did sound a little rude, but whatever, so did yours.
  18. QUOTE=hiesman;

    "Source of fresh air => fan>==> grow room that is sealed == fan>==>carbon filter====> away from grow room outside."

    What kind of filter are you using that it can be hooked up INLINE like this? Do you have a picture of it?

    This is my point is that most people including me, haven't seen a fliter that can be used like this. My filter can either be at the start of the duct, or at the end, but you can't hook duct up to 2 different parts of the filter. I suppose yours is quite different.
  19. I'm not hiesman so I can't be 100% sure, but what I think he's showing is the carbon filter (with a duct connection at only one end and capped off at the other) at the end of the exhaust duct - the last link in the chain. Air being blown into the filter passes through the carbon from the inside out and then out into the 'world'.
  20. #20 Martano666, Feb 11, 2010
    Last edited by a moderator: Feb 11, 2010

    Can't be. He said that the '====' marks are ducting. He has 'ducting' on both ends of the filter. To do it the way Heisman said, using a standard carbon canister, you would have to have the filter sitting outside of your house right? (whereever the canister sits is where the air is going to exit, when set up that way, no? I am pretty sure NOBODY is going to put a carbon scrubber on the OUTSIDE wall of their house. Or else he doesn't actually vent to the outside of his house, but rather, just in to a separate room WITHIN the house. (not a good idea) Plus he said he made one himself, so I suspect that it is different than the ones everyone has seen. It's a big secret though, he doesn't want to tell us. His explanations aren't very clear, except when he is talking about how huge of a grower he is. How many plants do you have Heisman? Was it 9 trillion..? lol.:D

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