What should i do for air ventilation in a 30x18x36 grow tent


I should be receiving my grow tent and led lights in a few days the only thing left for me to get is some thing to get air flow in my tent my tent is going to be 30x18x36, i am planing on growing x2 plants i have a 140mm computer fan and a adapter to plug it in the wall, i am planing on using it for a exhaust , how should i get air into the tent ? Should i just use the 140mm fan as a intake to get air into the tent and let the air get out from whatever openings that will be in the tent ? Or can you suggest a better solution ? I would like to keep smell at a minimum but i dont want to spend alot of money doing so

Recommended fan

You want to run a negative pressure inside your tent. Intake can be passive, but the exhaust should be from a strong enough fan – exhausting hot air out the top of the tent. You will probably need a centrifugal fan with a carbon filter and a controller.






What size ducting does the tent have at the top?



Maybe something like this with the appropriate carbon filter:



I’m not shure i didnt recieve it yet all i know is quictent make it and its a 30x18x36 mylar reflective tent, that ventilation system you linked come to around $200 , is there a ventalation system i can get for around $50 ? Also does ventelation effect yields ?


Yes it helps, if you don’t remove the heat your plants will die. Also your plants need fresh air.


Dont all led lights have a power supply system that automatically lowers the wattage input when the temperatures become to high ? Or do only some led lights have that feature? I was checking out a few lights and the vendor had it advertised as being 300 watts, and true wattage draw from 100 watt to 150 watts i got confused as to why the true wattage was from 100w to 150w and i asked the vendor why and he said because there led light has a smart power supply system that automatically lowers the wattage input if it gets to hot, but ether way you dont want that feature to kick in because you want the led light running at peak performance all the time with low temperatures , but i think that feature would pervent the plants from completely dying , correct me if i am wrong


There is a lot of flat out lies and misrepresentation in LEDs, especially by the floor vendors to justify their outrageous prices. It is part of the reason LEDs have had a bad reputation for so long. You can see this in the way most LED systems like the $65 one I recommended to you cost easily more than twice, or even 3 of 4 times more expensive, usually around at least $200 or more, for the same powered light.

LEDs are not magical nor necessarily that different than other forms of light.

Any temperature control in the LED itself – is only to keep the LED from burning out. It doesn’t care if it is too hot for your plants, the LED might do fine as high as 150-200 degrees Fahrenheit. And yes, if it drops power to drop heat, then yes, the light intensity will drop as well, which means less photosynthesis and kind of defeats the purpose of having enough watts per square foot.



i have a 36x18x63 inch tent with a 4 inch inline bring air from outside tent and a 6 inch carbon filter on top putting hot air out and run 700 watt mars2 and 2x250 watt cfl and my temps run about 77-81 degrees


I am growing in a room that measures 5’ x8’ but currently only useing an area of 2x8 with three plants. I am using a 600 watts of t5 flouresent light.I am curently using a 70cfm bathroom fan for ventillation and still having heat issues want to add more but noise is an issue. I want to err in too much fan and be sure i can control temps. Plants are 12" tall and very bushy. More better than less?


I wouldn’t add more exhaust fans, just get a better exhaust fan, a good centrifugal fan with a much higher CFM rate would probably do the job and be quieter than a “bathroom” fan.




What are the specs on your fan? CFM?

Do you know the actual draw of all your lights, in watts, combined? That would be some good info to know.

Also, the actual watts of the 700 watt LED MARS2 by itself?



Looked up your Quictent and this is the listed specifications


30" x 18" x 36"

210D oxford cloth

Interior Lining
100% reflective waterproof mylar

White steel pole, Φ16mm x 0.8mm (thickness)

Main Access Doors
1 x Front

4" Port
1 at back

6" Port
2 at sides

8" Port
1 at top

Passive Ventilation Windows
3 with mesh vent

Again I am also new to this so please use what I report with this in mind.

Found this formula for “standard rule of thumb” reference on the CFM needed
to remove all air in 5 min.
Cubic Feet Div. by 5 = CFM Needed to remove all air in 5 Min.

Cubic feet is calculated by using the inch dimensions as follows.
Multiply Length x width x Height and then div by 1728
(12in x 12in x12in =1728 cubic inches)
so 30x18x36 = 19440 cubic inches, now Div by 1728 = 11.25 cubic feet
EDIT: 11.25 Div by 5 = 2.25 CFM
Result is you would need 2.25 CFM TO REMOVE THE AIR and The intake
should be 1/3 the strength of Exhaust or 0.75 CFM.

I suspect the smallest inline fan you can find will work and you will probably
need one with speed controller to adjust them down.

EDIT Please read below

Hope someone else chimes in as I see I forgot to divide the CFM answer by 5
but that would result in a 2.25 CFM for air removal, this sounds low so maybe
I don’t know.

Ok just did a visual look at the size of the tent (2.5 feet by 1.5 feet x 3 feet)
and now agree with the numbers, sounds right at 2.25 CFM


A good carbon filter might restrict airflow enough, that not just “any” inline fan will do. Make sure it is at least a centrifugal fan, standard inline fans just don’t have enough draw to work under much “restriction” as is found with a carbon filter.

A 8 inch computer tower fan fit in the 8" port at the top might work, without any resisting carbon filter, if smell won’t be too big of an issue.

If a centrifugal fan is used, you don’t need to get a 8" one, get the smallest, a 4’, and make an adaper to use it with that port at top. 8*’ fans are just way too expensive and you’d only need it if you were using a HPS light in that tent.

And yes, you’d probably need the speed controller even with the least expensive centrifugal, or sometimes they are called “vortex” fans, as you probably wouldn’t need to run it at max speed/watts.



440 cfm actual wattage 850 watts mars2 700 actual draw 350 2x250 cfl total 850 watts