Help!!!!! Ventilation!!!!!!!

... helps if we actually have sort of an idea of what your workin with. Except the approx size u have. If your in a room, use a window or vent into a diff room of your house if you cant vent outside. I have a closet grow thats vented into my house with a fan from walmart taped into a hole in my grow box and my intake is another hole with a furnace filter taped over it lol so just use your imagination. Or take some pics and upload them that would gets you the best results to be honest.

greed sometimes u need more then the size to be most efficiant
i wish u most vest of luck with r grow in hopes that it gets u very stoned

you need minimum 500 cfm out 500 in. then you also have to consider if youre using vented hoods and what type of room.

You will need a min of 500 out and 400 in. Keep a neg air flow. Also with 16 plants the smell is going to be strong so if you need to add a filter it would be better to have hi flo 8inch fan around 740 cfm and a filter with 600 cfm air flo.

are they feminized seeds?

dont let the temps get over 90 degrees you should have set up the lights first to see how hot it gets.

bottom line for 4 600w is independent cool tubes with decent cold air supply, secondary extractor for the tent / grow area.

http://www.ebay.co.uk/itm/6-RUCK-INLINE-EXTRACTOR-FAN-150L-715-m3-h-HYDROPONICS-/280648588932?pt=UK_HomeGarden_Garden_PlantsSeedsBulbs_JN&hash=item4157f59e84

I personaly don't use inlet fans, passive inlet of cool outdoor ducted air works for me. If you are in winter you will be fine, summer temps (70+ degrees) it borders on impossible keeping cool without a/c unit or 2. Keep you inet low and extractor high. Clean fresh cool air in, dirty warm air outside.