Fans Off during Dark Cycle? Plants Give Off CO2 at Night?

is it ok to turn off my fans/exhaust ventilation during the dark cycle? i was told from the dude at the grow store that plants give out co2 at night and it is perfectly fine leave the fans off and infact its a waste of good co2 if you dont....any truth here? experts please respond! +rep

yes, no exaust durring dark period

While he didnt lie to you, it really depends on your setup. Keep in mind that CO2 is heavier than air, and sinks. Most exhausts are very high up in the room. If you, like me, only have your exhaust fan on a low setting, it really doesnt make a difference. But, if you got a very active air, air-tight grow area where literally all the air is being pumped out of the room when your exhaust is on, then yeah...turn it off during the dark.

Buds Mcfadden said:

While he didnt lie to you, it really depends on your setup. Keep in mind that CO2 is heavier than air, and sinks. Most exhausts are very high up in the room. If you, like me, only have your exhaust fan on a low setting, it really doesnt make a difference. But, if you got a very active air, air-tight grow area where literally all the air is being pumped out of the room when your exhaust is on, then yeah...turn it off during the dark.

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what didnt make a difference? turning the exhaust off at night?

i do have a 5x5 tent within a room, the tent has exhaust @ 400cfm and passive intake blow right back out into the room. The room can be sealed but i keep the door open to allow fresh air to come into the room and into the tent. so an idea is at night i could just shut the room door? keep the exhaust ON and just keep the co2 circulating in the room...usually i leave the rooms door open so it can pull in fresh oxygen....

i am worried about too much moisture building up if i leave the fans off at night....could lead to mold and other issues so ive heard.



one idea was if i do keep the lights off is turning the light on within

plants give off co2-

who knew?
you must have circulating air. unless your plants are willow wisps, you are asking for a multitude of problems(as seen evrywhere on this site). plants only use the carbon during photosynthesis.
one way people take advantage of this is by running staggered rooms. they maintain circulation between the two. when lights are off in one they pull that air to the other, and vice versa.

unless your grow is dialed in(read feeding nutes at three times normal levels with explosive growth) you will not realize much benefit from the saturated co2 levels.

I am not sure about plants giving off co2 at night. My understanding of photosynthesis is that plants breathe in co2 and give off o2. I could be wrong, since it happens frequently.
My exhaust is on the timer with my lights. My plants are healthy and the stalks are strong. If you wish, use a small 15 dollar oscillating fan and turn off the exhaust. Waste of electricity, IMO.

No, bad idea. Your plants are most susceptible to mould in the dark period, leave it on.

i need more help here guys im still confused on what is best! thanks! +rep

here lets make it simple. Fuck the fan on the dark cycle for veg but you NEED the fan ON in the dark cycle for flowering. during veg mold is not really an issue. Once buds start to form there is more moisture in the room due to the moisture in the buds. No fan on the buds at "night" will give you mold problems. So here it is again.

VEG-NO FAN
FLOWERING-FAN

A cheap oscilating fan is best. The tall vertical ones for cabs. They are slim and take up no space yet move tons of air. If you get a digital one you will have to manually turn it on and off cuz on a timer when the power shuts off and comes back on my fan don't. Maybe its just my fan but I doubt it. So during flowering it will have its own 24/7 outlet so I dont gotta fuck with it. AND YES, plants to give off co2 at night. why you ask? During the day plants take in c02 for the photosynthesis process (breaking down sugars) at night the process is revrsed because there is no light to promote photosynthesis and in return emit c02 back out into the enivronment. The is called respiration. Plants in general do emit more o2 than Co2 BUT they do emit BOTH. So, you both are correct.

hitthisshit said:

here lets make it simple. Fuck the fan on the dark cycle for veg but you NEED the fan ON in the dark cycle for flowering. during veg mold is not really an issue. Once buds start to form there is more moisture in the room due to the moisture in the buds. No fan on the buds at "night" will give you mold problems. So here it is again.

VEG-NO FAN
FLOWERING-FAN

A cheap oscilating fan is best. The tall vertical ones for cabs. They are slim and take up no space yet move tons of air. If you get a digital one you will have to manually turn it on and off cuz on a timer when the power shuts off and comes back on my fan don't. Maybe its just my fan but I doubt it. So during flowering it will have its own 24/7 outlet so I dont gotta fuck with it. AND YES, plants to give off co2 at night. why you ask? During the day plants take in c02 for the photosynthesis process (breaking down sugars) at night the process is revrsed because there is no light to promote photosynthesis and in return emit c02 back out into the enivronment. The is called respiration. Plants in general do emit more o2 than Co2 BUT they do emit BOTH. So, you both are correct.

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thanks, i understand leaving fans on but i am talking about exhaust my bad for calling it "fans"....is it better to have the exhaust on or off during the night? is there any benefit to leaving the exhaust on vs off?

solarguy said:

is it ok to turn off my fans/exhaust ventilation during the dark cycle? i was told from the dude at the grow store that plants give out co2 at night and it is perfectly fine leave the fans off and infact its a waste of good co2 if you dont....any truth here? experts please respond! +rep

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Think he means to give Co2 at night? because plants breathe Co2 not produce it. Plants produce O2 so if I understand right... I would use a timer to have Co2 come on and fan off for a while like for instance... I turn off exhaust fan then fill room to about 1500 Co2 and then let sit until it goes down to about 900 that takes about 2-3 hours depending. Now C02 is heavier so may be a good idea to have a fan on blowing air upwards and another to circulate it. I would not run Co2 while exhaust is on you would be just wasting your Co2. Also just from experience most hydro stores will give you some of the worst advice ever ( most cases ) although not saying all will just my experiences I have had many people at hydro stores give advice only to research it to find out it was so far off in most cases. So be careful for that matter of taking any advice try to find people who have done it before personally and have pics or something. Also it is better to have Co2 on during the day or lights on period as photosynthesis will increase Co2 intake. Not saying you can not do it when lights are off ( because I do ) but science says that plants only metabolize when lights are on and just guessing that they would use the Co2 better with less waste. ( not researched though )

solarguy said:

is it ok to turn off my fans/exhaust ventilation during the dark cycle? i was told from the dude at the grow store that plants give out co2 at night and it is perfectly fine leave the fans off and infact its a waste of good co2 if you dont....any truth here? experts please respond! +rep

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for my grow lights out so are all fans..