Air Exchange And Co2 Requirements.. Science?

  • Thread starter Trudope
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Trudope

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Hi All,

New grower here, will have a timelapse journal up as soon as I complete my grow! Until then, I've been wrestling with a few thoughts on air exchange and the current stated exchange x times per minute rule of thumb.

I've read through countless of threads and forums that recommend that one should calculate the volume of the grow tent, then choose a ventilation fan that can exchange the air in the tent 5-10 x/ minute. The reason being is that it exchanges heat and CO2 which supposedly gets depleted really quickly...?

I find it hard to believe. I'm typing this up as I stare at my three vegging Jack Herers that are about 1 feet tall in a 4x4x6 tent. Here's my conundrum summed up: If heat and humidity are controlled for, how often does one need to exchange CO2? With the way my tent is setup, I have a side sill open and a large fan within the tent constantly blowing. With a passive intake (no fan pulling) I can't forsee the plant exceeding the amount of CO2 that is coming in-- albeit only a small amount of air gets in passively. Why? Because, I can imagine that I would be able to exercise in the tent and not use up all the oxygen even though its sealed everywhere except for the passive intake (it's a decently big tent). One counter argument would be that there is very little CO2 in the air compared to O2-- however, I'm assuming the plant has a very slow metabolic rate, so everything said, it should be even.

What do you guys think? If heat, humidity and all other variables are controlled for EXCEPT for CO2. How often should you be running your exhaust fan? If you post a rule of thumb, could you please elaborate on your line of logic?

edit It's my first grow and I'm trying to sift through all the bs I read online. So far, I'm 3 weeks into veg and only run my exhaust every 4 hours (pulls 442CFM) for 30 minutes to control the heat in the room (DWC). My plants are super bushy and healthy. So I'm wondering if running it more often would be of benefit..
 
Dbear180

Dbear180

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Like demon said avg co2 ppm is around 400.
When we add co2 I think of it like an athlete taking in bottled oxygen, it's not totally necessary for them to breathe through that mask, but it does help. That's why we bump co2 up closer to 1500ppm. I would just keep your intake on a timer & run it as often as necessary to keep things cool. Worry about co2 enrichment once you've got a few grows under your belt.
 

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