Marijuana circulation


A question from a fellow grower:

I am using 4ft T5 lights for veg since I am in no hurry. I plan to flower with 1000w hps. I am growing in organic soil that has all the nutrients in it for the first few weeks. I am also using the organic line of general hydroponics for feeding. They are growing amazingly and I have topped it various times. I am also testing the pot sizes; short 1gal or talk 1 gal start after germination. Then I transplant to 3 gal tall pots.

What do you opine? What do you think of the pot size?

I am growing in a basement closet with one stand still fan. Do you think I should invest in a more robust exhaust/circulation system? My temps are 77 f and humidity 55%.


Are we talking aprox. 4x4 growing area/canopy? I personally think 1000w HPS is over kill in an aprox 4x4 or up to a 5’x5’ space. I personally like 600w HPS for up to 5’x5’. The one fan would be fine for a aprox 5x5 space but how does air get in or out of the closet? Do you keep the door closed? One 6 inch exhaust duct fan with ducting will do fine, it will suck plenty of fresh air in under the door, the way most closet doors are hung above the floor. Also you can just close the door during the dark period as they don’t really transpire or breath as much at night. I’m more of a DWC hydro guy so I’ll not comment on soil container size.


hi I want to know how much air to fill a 1200 x 1200 grow tent so how long should I leave the intake fan on for to fill this space and then how long before I start the out take fan so how long will it take for the plants to consume this amount of air and should I increase the amount of air as they get bigger as they will consume more.


Container size is perfect.

Yes; You need a 6" exhaust fan.

100 watt is fine as long as you can manage the heat.

It is 77 degrees with a T5. It will be 95 degrees with a 1000w Hope you can draw from cool air.


A 1200 x 1200 what??? feet, centimeters, inches?

The formula for the size exhaust fan you need in a given space is determined by this formula.?

L x W x H to determine total Cubic feet of the space.
i.e. a 12’ x 12’ room with 7’ ceiling would be: 12’ ‘x 12’ x 7’’=1008CF This means it would take slightly over 2 minutes to completely exchange the air in your space using a 450 CFM exhaust fan.

A 650 exhaust fan would exhaust this space in 1.5 minutes. Hope this helps


Hi its 1.2 meters x 1.2 meters or 1200 cm
So as the plants get bigger should I exchange the air faster than say every 2 minutes as the plants will be consuming more CO2

Not that good at maths so L 1.2 m X W 1.2 m X 2m H = 288 and I have a 100 mm intake and 150mm exhaust 140 litres a second so how do I work out how many minutes I need please

I appreciate your help also how can I change my profile photo as this is not the photo I want on here


If you are running Co2 then you want to exhaust at a higher temperature. You do not want ot waste co2 so this something you need to figure out accrding to the formula I vae you.

1.2 meters is aprrox. 4’ feet. so 4 x 4 x? height?