# ventilation fan question



## jungle (Aug 25, 2009)

flowering room  4' x 4' x 7'
600 watt air cooled light
Question is?  If I build a carbon filter by TLToker, found in the stickies..what size internal exhast fan will i need to push air out through this filter and what size external fan to push air in..to keep good air circulation.......brands or names are fine....thank you


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## pcduck (Aug 25, 2009)

Your room is 112 cu. ft. most grower like to circulate their grow room any where from 3 to 5 times per minutes. If you were to circulate your room 4 times per minute, you would need a fan that has a cfm rating of 448cfm.

On the carbon filter I pull air thru my filter and just use a passive intake.


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## jungle (Aug 25, 2009)

I think your saying to pull the air out through the filter with a 448cfm fan.
Then do I push air into the room with a 448cfm fan also?


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## pcduck (Aug 25, 2009)

Yes I pull air through my filter.

You can use a fan if you want. I use a passive intake, a 6" round hole with no fan


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## jungle (Aug 25, 2009)

i guess i don't know what a passive intake is....i understand what to do and how to use  the carbon filter...and what size fan (448cfm)  extract air from the grow room..through the filter....It's the other part I don't quite understand......what do I need to place fresh air into the room.....I don't know what you mean by having a passive intake. a 6" round hole...with no fan.....I'm assuming if I'm using a 448cfm fan to pull air out of the room and through the carbon filter.....then it would be ok to use a 448cfm fan to put air into the room...would this fan be placed on the inside of the room pulling in fresh air from outside..or should it be placed out side pushing air in......If this is correct than the carbon filter doesn't really empede air flow going out so the same size fans are ok for good ventilation filtering air both in and out


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## pcduck (Aug 25, 2009)

passive intake is an intake that has no fan forcing air into the room

passive intake = just a hole that allows air to pass


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## jungle (Aug 25, 2009)

ok I see.....so if I'm pulling air out with a 448cfm...all I need is a 6" hole some where in one of the walls to the room....air will passivly enter through this hole,,,because of the suction going out? Which raises my final question....light leaks...how do I prevent light from entering this 6" hole....and if one uses ductwork..and fans....for removing and repleneshing oxegen....what stops light from traveling throgh the duct work or the 6" hole in the wall and onto the flowering plants? This grow room will be in a basement and inside the room will be dark hopefully with no light leaks...but out side the grow room even with lights out there could still be some light coming through some crack in the basent walls or floor or something..


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## pcduck (Aug 25, 2009)

Put an elbow on it and paint the inside black. Light travels in straight line and will not bend around the elbow, and or a filter depending on where you are drawing your air from. If from outside I would put a filter to stop bugs.


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## jungle (Aug 25, 2009)

Thank you.....I never heard of a passive intake before.....I can put an elbow on it to block light...have it painted....use the 448cfm with homemade carbon filter...for outgoing air...thanks so much


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