How important is air exchange per minute?

I see 2 reasons why air exchange is important:

1) to keep temps down by sucking out hot air and sucking in cooler air

2) to have fresh air come in for proper co2 levels

Here's my scenario and question:

My tent is 4x4x8, which is 128 cubic feet and I have an exhaust fan rated at 128 CFM, that means the air in my tent will be replaced once every minute. With this amount of air exchange, my temp is stable at 79-83F. I have a co2 tank outside my tent set on a timer; 15 mins on, 30 mins off. There is a tube connected to the tank going into my tent. With this timer setting, my co2 levels stays between 700-1200 ppm.

Is it necessary to upgrade to a stronger fan with a higher CFM? I have plenty of air movement inside the tent with 2 fans.

If you are happy with the air movement there is no need to change it. There is no hard and fast rule on how much you need to exchange, as long as you are exchanging it and the temps are under control. I have a 4x4x6.5 tent and use a 200cfm which works for me. WIth 2 6 inch clip on fans inside moving air around.

I have an exhaust and an intake fan solely for air Exchange. I run them about 10 minutes every hour. Plants seem to like that. I use AC to control Temps.

So you're only exchanging the air 10 minutes per hour?

I have an 8 inch 720 cfm for my tent of same size.
You need to account for resistance in ducting and filter if you have one.
If you have hid lighting my guess is your temps will be too high in flowering.

keepsake said:

. With this amount of air exchange, my temp is stable at 79-83F. I have a co2 tank outside my tent set on a timer; 15 mins on, 30 mins off. There is a tube connected to the tank going into my tent.

Click to expand...

Pretty sure its not the greatest idea to be exchanging air that much and running an exhaust system. Some would probably consider that wasting your co2 tank. I have read that there all people who swear by burping their sealed room every now and again, but exchanging air every minute is too much while running a co2 tank.

a mongo frog said:

Pretty sure its not the greatest idea to be exchanging air that much and running an exhaust system. Some would probably consider that wasting your co2 tank. I have read that there all people who swear by burping their sealed room every now and again, but exchanging air every minute is too much while running a co2 tank.

Click to expand...

What do you think a good exchange rate would be if running co2?
I figured once every minute wouldn't be too bad but maybe it is?
If I could keep my temps stable.. is there any purpose for air exchange if I already supplement co2?

keepsake said:

What do you think a good exchange rate would be if running co2?

Click to expand...

I don't know honestly. My exhaust only comes on when my room gets hotter then my desired set point on my controller (84 degrees). I have read about gardeners burping their room once an hour. Remember there are many many ways to grow. My way just works for me, others works for them.

keepsake said:

If I could keep my temps stable.. is there any purpose for air exchange if I already supplement co2?

Click to expand...

No. I believe there is no reason.

Ah


I see the light now. Anybody wanna object to the notion that air exchange is not needed if temp & co2 levels are good?

keepsake said:

Ah


I see the light now. Anybody wanna object to the notion that air exchange is not needed if temp & co2 levels are good?

Click to expand...

Im talking about supplementing co2 only.

Yeah but I said if temps are good AND co2 levels are good... is there need for air exchange?
You said no.
Im wondering if anyone wants to object with some reasoning?
Obviously there should be good air movement provided by fans as well so there is no stagnant air.

keepsake said:

co2 levels are good.

Click to expand...

800-1200 ppm is what we are talking about. Im saying no need for air exchange if co2 are at those levels and said temps are good.
No one will disagree friend. Its in every bible around. The filter will then be used for scrubbing air inside the said grow room.
Remember the op states he/she has a bottle injecting co2 into his/her grow.

Oh that's fantastic.
I was over here worried about trying to replace the air inside my tent faster than what it currently does when I don't need to because my temps are good, co2 is 800-1200, and air movement is good.

Saves me a few hundred bucks for a stronger inline fan.

keepsake said:

Oh that's fantastic.
I was over here worried about trying to replace the air inside my tent faster than what it currently does when I don't need to because my temps are good, co2 is 800-1200, and air movement is good.

Saves me a few hundred bucks for a stronger inline fan.

Click to expand...

Again like you posted, others may not agree with what I'm saying. Always nice to hear from others on these forums.