Air intake / outtake through open window. No AC.

Hi guys,

Im growing inside tents but still a lot of smell can escape my grow room. Also my girlfriend likes to smokes A LOT. My grow room door is as sealed as possible but still a lot of flowerish smell can escape. My only option (at least I think it's my only option) is to get negative air pressure inside my grow room.

I can't install anything outside of my apartment/window because where I live no one does that. It would be super suspicious. I was thinking about building something like this:

(the mosquito net is there so no one can see what's happening behind it).



There are to possible scenarios: 1. it works 2. it doesn't work (the same air just keeps circulating on and on...).

I have no idea which scenario is going to happen with this kind of system and I was hoping that someone here could help me. It would suck to spend + 200€ and 6 hours of work for nothing.

If this system doesn't work I think I need to install only exhaust to that window and take air from somewhere else? I was thinking about drilling a hole to a wall so I could get it from another room. I own this apartment so I can do some modifications.

Thank you for your time.

I thought that my previous plan might be way too complicated. After all all I need to do is achieve negative air pressure into my 4m x 4m room (13 x 13 feet).

I was thinking about these portable ACs that has a tube for exhaust. If I buy the most powerful model (or 2 of them) is it capable to push so much air out that it would cause negative air pressure into my small room?

Like I said I don’t know how these machines work so if someone could show me an AC unit (portable or not) that can do what is needed. A link would be perfect so I can check out the specs. and maybe even buy one.

This post confuses me, are you asking if a portable AC can be used as your exhaust?

I think you're overthinking it, exhaust through a carbon filter out your window (there are ways to do this discretely) and use passive intake for negative pressure. Simple. Use the AC to cool the room.

Negative pressure only means you exhaust more air than you intake.

Negative air pressure is exactly what Im after. Also, I would like to know are portable ACs capable to do this.

If portable AC is not good for this setup I guess I buy one more inline fan.

Ac won’t work well it will but it will also suck the stank air outta your room and will smell outside the window. Use a big exhaust to vent out window and find another way to intake. Or if it’s winter exhaust into your house to keep it warm and use window for intake.

The way you have your pictures you will be short circuiting so to say your air. Your going to be pulling your exhaust back in through your intake because their right beside each other

You don't want an intake fan, period. Just exhaust.

Get a carbon filter and exhaust out of the room either back into the apartment for added warmth or outside. This will create the negative flow. You are overthinking this all.

just get a carbon filter canister and a duct fan and expel it outside. Canister goes in the tent, ducted to the fan, ducted to whereever u want it to go. bathrooms work, just turn on the exhaust fan allow the air intake to come from inside where its more consistent. If you have your exhaust and intake right next to each other like that.. that could be an issue, eh?

if use use a carbon filter and exhaust the air out of the window (you can do this discreetly) the negative pressure this creates will be enough for the room, This is because your exhausting more air than what can come under and around the door and window frame.
This means NO intake fan.

A portable room A/C will cool or heat a room it wont effect pressure or smell.

I know the basics of negative air pressure. Everything is fine inside my tents with inline fans + passive intake. The problem is that my grow room leaks some smell so need to get negative pressure inside the room.

I will build and exhaust fan and drill few holes to get passive air in the room. If someone can give tips how to do this discreetly (basically how to push the hot air out of your window discreetly) that would be awesome ( Lucky Luke ?). At least in winter time it creates "heat vibration/flutter" in the air and that might be a problem.

Thank you all for your great tips.

If in cold climate just vent inside. I do this in winter here for free additional heating. Right now it is -20c here now.

I am not understanding why the room that your tent is in has odor. if there is odor then your basic understanding of the tent negative pressure is not working. If your tent sides are all sucked in tightly then it is working, there is no way odor is coming out unless you open up the doors.

Are you running carbon filter?

kingtitan said:

If in cold climate just vent inside. I do this in winter here for free additional heating. Right now it is -20c here now.

I am not understanding why the room that your tent is in has odor. if there is odor then your basic understanding of the tent negative pressure is not working. If your tent sides are all sucked in tightly then it is working, there is no way odor is coming out unless you open up the doors.

Are you running carbon filter?

Click to expand...

Runnin 2 carbon filters and quality inline fans + good tents.

I need to nurture the plants (open up a tent) and like I said in my first post we smoke A LOT (inside the room)... Harvesting/Trimming also produces a lot of smell. I can't do that for 12 hours inside a small tent.

If I would only vent air inside it would create even more positive air pressure and the door would leak even more?

I managed to seal my interior door better so the problem is not that bad anymore. Still it would be better to achieve that negative pressure. One problem is that I need to keep negative air pressure inside my apartment (other parts of my apartment). Otherwise all the air and smell would escape to the stair-step (through mail slot etc..)

-> Negative pressure inside apartment (except grow room) -> Leaking air from grow room.

EDIT: Everything would be OK if we would smoke inside the growing tent and do all the trimming inside the tent. Of course this is not an ideal solution

How old are your carbon filters? Either they are old or too small for your fans. Smell shouldn't be getting out of the room either way if it's ventilated properly.

n0thing said:

How old are your carbon filters? Either they are old or too small for your fans. Smell shouldn't be getting out of the room either way if it's ventilated properly.

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Darn... I try to be as understandable as possible now.

NO smell can escape my tents if they are sealed/closed. My filters work fine (3 - 9 month old filters). ALL the smell that disturb me come from:

1. Smoking a ton of weed a day (in grow room)
2. Nurturing the plants during the grow
3. Trimming during harvesting

Because of this negative/positive pressure all that smell travels out from the growing room to other parts of my apartment. I guess this can be fixed only by achieving negative pressure inside my growing room. Im building some sort of exhaust (through window) to achieve this. It would be nice to get few tips how to do this discreetly (get rid of "heat vibration/flutter" if possible. This is my main concern). Also other tips for discreet exhaust though window are very much appreciated.

Your situation is making a simple solution very complex. If just exhausting warm air is going to have people questioning you, you need to cool the air to outside temps...

Your only other option is to get a big floor standing carbon filter and a 1500CFM+ filter running in "SCRUBBING" mode. That is air is recirculated at high flow instead of exhausting it.

You need something like these CAN 100/125/150 http://canfilters.com/filters/can-filters.html with like a 12" or 14" inline sitting on top of it and just filtering 24/7.

kingtitan said:

Your situation is making a simple solution very complex. If just exhausting warm air is going to have people questioning you, you need to cool the air to outside temps...

Your only other option is to get a big floor standing carbon filter and a 1500CFM+ filter running in "SCRUBBING" mode. That is air is recirculated at high flow instead of exhausting it.

You need something like these CAN 100/125/150 http://canfilters.com/filters/can-filters.html with like a 12" or 14" inline sitting on top of it and just filtering 24/7.

Click to expand...

That is actually very good option. Thanks for the tip. This "solution" brings 1 more issue and that is noise. If I install very powerful inline fan my neighbours will definitely hear that. Our walls are like cardboard paper and you can hear neighbours conversations trough walls etc..

I might try this with smaller filter + "normal inline fan" (360m3/h) and see how it works. If that doesn't work I need to upgrade or do something else. Does anybody know what are the most silent inline fans on the markett? It needs to be at least 360m3/h. Im using Prima Klima 220/360m3 at the moment but I want to change all my fans at some point.

It sucks to live in small apartment. Im definitely going to buy a big house as soon as possible.

-DreamK said:

That is actually very good option. Thanks for the tip. This "solution" brings 1 more issue and that is noise. If I install very powerful inline fan my neighbours will definitely hear that. Our walls are like cardboard paper and you can hear neighbours conversations trough walls etc..

I might try this with smaller filter + "normal inline fan" (360m3/h) and see how it works. If that doesn't work I need to upgrade or do something else. Does anybody know what are the most silent inline fans on the markett? It needs to be at least 360m3/h. Im using Prima Klima 220/360m3 at the moment but I want to change all my fans at some point.

It sucks to live in small apartment. Im definitely going to buy a big house as soon as possible.

Click to expand...

Get an oversized fan and a Variac controller and dial the voltage down to something more quiet, say 50% - 60% instead of running one that matches CFM output at 100%. My 6" 460 CFM is 58db but running it at 90v is 49db. Maybe just run it when you are all smoking up or before opening the tent?