a question about venting.

I was wondering if I would need a cool tube for my size light and tent. If I am using a carbon scrubber inside my grow tent? The tent is 36x36x60 and I will be using a 250 watt light. I was curious if the carbon filter would keep the temps down on that size light or do I need the cool tube also?

you sound lost. a carbon filter will not cool anything. it is for removing odor, only.

ok but wont it suck the heat out also?

If you buy a carbon filter on one of the 4 inch inline fans cant you have it blow the exhaust out of a hole thus it is ridding the smell and working as an exhausy for heat and air...i dont know how many cf your tent is but i read that.u want the exhaust fan to.be able to cycle the air ouy of the box a few times an hour

Wouldn't pulling the warm air out of the room be cooling it as long as the intake fan/vent has a lower temp air coming in?

In my room I have a fan pulling in air from a upstairs room at 70 deg. 600watt hps bulb with a reflector no cool tube. Also a carbon filter with fan pulling air out.

My temps stay around 74ish 68 low and 78high

co2 will let you run higher temps i believe

thats what I was thinking. I thought the the fan on the carbon filter would pull the heat out also. Or do I need a fan just for the carbon filter and a fan just for exhaust?

I strongly suggest you get the cool tube with a inline fan to exhaust the heat out regardless the size of the box. Your suppose to attach the carbon filter to an inline fan to suck the smell through the filter and out the box. The filter is not a fan.

Hey look up diy carbon filters you can make one with a man

texastiger707 said:

thats what I was thinking. I thought the the fan on the carbon filter would pull the heat out also. Or do I need a fan just for the carbon filter and a fan just for exhaust?

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You were thinking correctly. The exhaust fan pulls stale, warm air out and sucks in fresh cooler air. It will lower the temps. Grows in a 4 X 4 tent can be kept sufficiently cool thru the exhaust process described above without a 'cooltube' even with a 400 Watt HPS light.

timbo123 said:

You were thinking correctly. The exhaust fan pulls stale, warm air out and sucks in fresh cooler air. It will lower the temps. Grows in a 4 X 4 tent can be kept sufficiently cool thru the exhaust process described above without a 'cooltube' even with a 400 Watt HPS light.

Click to expand...

ok thank you very much.

what cfm fan would I need for a 250 watt light in a grow tent that is 36x36x60?

erm ok lemesee, you need to copy nature inside thats the goal, atleast if you want to grow living plant`s in a tent ..

you will need a ventilation for air/co2 circulation beside the light/fan/grow medium/nutrients aso.

basic thing it will do is exchanges the air/co2 and plant need both .. it will also exchanges the hot air ..

when flowering they will stink ... a lot !
and a carbon filter is the most effective way to control that by adding it to your ventilation system so the air that is pulld out of the tent have to pass the active carbon






that will remove 99% of the smell but is also make your ventilation 20-30% less effective (pure logic as it have to pull the air through a filter) and that will if anything make your temps go up not down ..

a cool tube is a very good idea a cool hood is even better as it have a better foot print and spread the light out more, HPS and MH light do get hot so a cool tube/hood will help you get a more trouble free grow, beside that it will allow you to keep the light closer to the plants and that really do make a big different


I run a 600W and I had problems this summer with temps reaching +33C and even after the summer peak I had +30C after I made a cool hood for it



my temps drop from +30C to 26-28C and I can keep my light at 12-15" instead of the 18-22" before the cool hood cam on


here is a chart that show you how much light a HPS provide at different Watt and distance

View attachment 2427383


weed is a light loveing plant and need atleast 3-5K in Veg and +10K in flowering as a rule of thump ..

beside the 6" ventilation I use to pull old/hot air/co2 out of my grow room/cool hood I also run a fan in there to cool the hood from outside and blow the hot air away from my plants and also to make some wind in there (I don't add the carbon filter before they begin to smell as filter have a life time on about a year of running so don't make sense to use it up when there is no smell to remove and it also put more pressure on the ventilation)





try to keep the temps around 75-80F somebody did talk about Co2 and sure with that the prime temp is a bit higher at around 85-90F but only make any sense to use if every thing els is spot on, or you might aswell use the money on a nice cool hood and a good 6" ventilation with speed controle ..