is ventilation really a must?

Hey all

So, i'm doing a bit of planning for my more recent space, and have come to the point where I have to make a decision.

My plan is to basically put all the environmental controls in this space, I'll be able to keep the temp/humidity/co2 level exactly as I want it. The thing is, I dont want to ventilate the air a lot...intake and exhaust fans are the only part of this grow which might be noticeable...plus it wastes CO2.

so long story short, i'm planning on creating this perfect environment (with an exhaust for the AC unit of course) without ventilation. I figure if i'm supplying the perfect air conditions, there is no need to change the air on a regular basis. this will allow me to save money on CO2, by sustaining the CO2 levels for long periods of time without having to recharge the air because of a vent cycle.


now, i've run this idea past a few other growers...and no one agrees. they keep saying the air will get 'stale', and that new fresh air is vital.

I argue that i'm supplying everything in the air that the plant needs, and what exactly are they saying will be wrong with the air?

all they ever reply is that it will be 'stale'...I suppose there is some magical, unquantifiable ingredient in air which none of them know about yet have complete faith in.

so, anyone have input here? I'm still gonna do it my way, just wondering if someone knew what this magical ingredient in the air is.

You have to exchange the air.Plants use a certain amount of co2 but need fresh o2 also for complete photosynthesis and the air as others have told you will get stale and poison the plants.You get less yield and fluffier buds with slower growth rates. Thed co2 will be on only during lights on times.Exchange the room air every 2 hours and you ll be fine.Keep all air moving and a fan blowing up from the floor as co2 is heavier then air and will fall to lowest area so get it recirculated.

ok, so you're defining staleness as general loss of oxygen?

what about the fact that plants produce slightly more (on average) O2 than they consume?

also, with the normal air being 21% O2, even if the plant does consume a little more o2 than they produce...there will still be more than enough oxygen in the air.

so, I appreciate the response...but have to disagree.

Quite a different story on your cloning thread.. I guess finding some space to grow was on your priority list hah. Interesting idea for a grow though. The only thing I can think of that might help you control the variables, is ducting off 1/2 of the A/C units intake so that draws fresh air. I'm not 100% sure it needs to be done though as I've never tried a grow that controlled. Give it a shot and let us know!

Dr.Green said:

Quite a different story on your cloning thread.. I guess finding some space to grow was on your priority list hah.!

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well, if you check what I said it was "dont have time (I dont at the moment...hopefully in a few months) dont have the space at the moment (this thread is part of my research while planning my space, which is not suitable at the moment) and have no need (to clone from a fan leaf)

anyways, not being a prick, just dont want to be misunderstood


and I should mention (as I should have in the original post) that the AC unit will be inside the space, sucking the air from inside the chamber, and venting it out. hm...i'm realizing now that this will create a negative pressure, and air will be sucked in from any cracks in the door. I dont even know if I can make this thing airtight...guess i'll have to pick up a vacuum gauge or something.

anyways...I know the dogma, fresh air fresh air fresh air...but I cant recall ever hearing of an experiment like this. i'm sure its out there somewhere, but i've not seen it. although i'm open to any more rebuttals...this place is great as a sounding board.

Yes, turn the air over. Stay in that room with your plants without turning the air over for an extended period and see how you start to feel. Not turning the air may not kill them but they wont be as healthy as they could be.

I mean...I know. I know the normal dogma of this issue...of COURSE ventilation is good for a plant. I'm really just trying to make an educated quantification of the effect on the plant. I just dont see oxygen being limiting for respiration, even when the lights are off and photosynthesis stops.

is there any other way people identify stale? maybe like...higher particulates in the air? I need an air scientist up in here. is there such a thing?

im all for experimenting. But i spent the couple hundred for ventilation because that is what people who are growing lots of herb are doing.

There are some pretty easy ways to run a clandestine exhaust. i found a video on youtube which showed how. And there are pics in my grow journal is you wanna see a simple, cheap way to run an intake and exhaust to your plants.

TMB77 said:

I mean...I know. I know the normal dogma of this issue...of COURSE ventilation is good for a plant. I'm really just trying to make an educated quantification of the effect on the plant. I just dont see oxygen being limiting for respiration, even when the lights are off and photosynthesis stops.

is there any other way people identify stale? maybe like...higher particulates in the air? I need an air scientist up in here. is there such a thing?

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Well, have you ever been in a house or apartment that has been unoccupied and locked up for an extended period of time? Know that musty smell that just seems to hang in the air? Its kinda like that.

true example...but not the same. in that situation I'M in there, using oxygen and exhaling CO2, maybe my sweat gets evaporates and gets the air all stanky, etc etc.

also (obviously) dont forget we're only interested in what a plant needs from the air...in their terms i'd guess stale air would mean lessened co2, too much humidity, too high temps, etc. since i'm controlling all of that, I just feel like it would work just fine, especially considering the boosted CO2.

but yeah...I know what you mean by stale air, but we gotta think like herb!

TMB77 said:

true example...but not the same. in that situation I'M in there, using oxygen and exhaling CO2, maybe my sweat gets evaporates and gets the air all stanky, etc etc.

also (obviously) dont forget we're only interested in what a plant needs from the air...in their terms i'd guess stale air would mean lessened co2, too much humidity, too high temps, etc. since i'm controlling all of that, I just feel like it would work just fine, especially considering the boosted CO2.

but yeah...I know what you mean by stale air, but we gotta think like herb!

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Ok, then look at it this way. It is a living organism, it has some sort of waste. That plant does not want to be growing in its own waste product, just like you dont want to be in the room sweating like you mentioned. Like the saying goes, dont poop where you eat. Now unless plants are 100% efficient with what they consume that they dont have waste then thats a different story.

The exchange of air is need to keep correct o2 levels coming in and to rid the air of its lack of o2 as you said you want to pump in pure co2 which at correct levels mixed with need o2 is great for the plant. Overdose co2 and drop fresh o2 to the plants and you choke them forceing them to stress and die. If your room is large enough say 20 x 20 and your lights are all sealed and ducted out the room and you can control all air movement,dont use co2,use humidifier and dehumidifers and can constatly monitor the rooms air content then you can do as you want but do a simple expirement and see for yourself.Put 1 plant in a small grow box no air exchanges and pump it full of co2 do another in a similar box with intake and exhaust hourly with co2 and within days you will see the difference in the plants healths.

I'd have to agree with TMB77, because I've done it.
as long as you replenish the CO2 levels and keep other levels in check you will do fine.
YouTube - Extreme Grow Room Make Over Part 1
watch that and the 2nd part.
as long as you have good air movement within the room you will do great

Rob did you use exact co2 usage keeping the co2 at the needed 1200-1500 ppm or just add some unknown co2 amount in there and what size room was it?

FilthyFletch said:

Rob did you use exact co2 usage keeping the co2 at the needed 1200-1500 ppm or just add some unknown co2 amount in there and what size room was it?

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Speaking of this issue, I'm planning on using this controller, it employs 'fuzzy logic' to keep the room at the correct PPM and save gas, avoiding overshoot.

Sentinel CHHC-1 Day/Night Environmental Controller

I've grown a few crops with co2 & no ventilation. I used to think since I was adding co2 I didn't need to exchange the air, man I always, always had odor problems. I mean bad odor problems plus you could definitely tell the air was stale.

Over time I've changed my mind. Here's my flower room now.




No more odor problems & I don't get sick going in there. Without venting your room an pesticide, nutes, odor from the plant, etc, it just lingers in there brewing into toxic gasses. Well they may not be toxic but it sure isn't any fun spending any amount of time in your room. My plants & my nose have never been happier.

thats a nice setup you got, mclovin.

I appreciate your empirical evidence mentioned in this thread. I wonder what it would have taken to achieve that 'fresh' feeling without actual fresh air. perhaps some ionizers and air filters, i've already got a good carbon scrubber for odor.

anyways, thanks, rep +

I like your thinking, I'm trying the sam ething without AC right now. Your problem is that a portable ac will discharge air which in turn will reduce your co2 levels. I think the beast is beaten by making our grow space light cooling as efficient as possible i.e. cool tube, absolutly no leaks, insulated ducting etc. plenty of circulation fans and then there may still be a excessive humidity problem whaich will have to be dealt with. I don't think we need a full 15 min. exhaust every 2 hous, maybe like 2-5min. would do along with a co2 counter and controller along with backdraft dampers.

Good luck mate,
Unity

I have read before of sealed growing enviroments. But i can't say i have ever been in one myself. Article i read was in a "Maximum Yeild" indoor gardening mag, a guy wrote in asking how to do one as a demo in his hydro store. The answer was long but it was possible, i think he said you needed to have total control of Co2, humidity & temp + a carbon filter and ozone generator. But he certainly didn't make it sound impossible