Intake Fans / Opening Lower Air Ducts or Back Flap?

You want to keep a little negative pressure so that the odour keeps going out as well. If you dont want to buy a fan controller you can block the outgoing hole to decrease the amount of air going out or do the same to the intake to limit the amount going in. With sufficient intake air it decreases the need for added c02. Cheers

I have a Terrabloom ECMF 150 and love it. Best for the price and the adjustable speed is super helpful. It's also pretty quiet. A lot of reviews claimed that there was a loud clunking noise after a few weeks, but I've had mine running pretty constantly for almost a year and have had no issues or noise level increases. At about 10% power, it works well enough to create negative pressure in my 4x4. I like to have my fan up top blowing out and the bottom flap on the opposite side open. This makes sure that the air being pulled in has to travel the longest possible distance before being sucked out again. This way you don't have your fresh air sucked put immediately.

Hi fella, never done intake out take fans, I run passive. What I 'believe' or understand that the rule is generally the same, you want to still create that effect of the out take being slightly more powerful then the intake, that's just what I perceive from research but I'm sure some more expirienced growers in this area will chime in and correct me if I'm wrong!! Happy Growing 👍