Exhaust Fans & Air Circulation
Exhaust fans are an extremely important part of any grow room, box, or tent. Exhaust fans are going to remove the heat created by your grow lights and other electronics you might have running. They will also help bring in fresh new air by creating negative pressure. In turn you don't really need an intake fan you just need an intake port where fresh air can be pulled in from the negative pressure created by your exhaust fan. Without an exhaust fan your grow area temperature will sit to high for your cannabis plants and be almost impossible to control.
In order to decide what size exhaust fan you need, you'll need to calculate the total cubic feet of your grow space. For example a grow tent that is 4 feet by 4 feet by 6 feet tall would have a total of 96 cubic feet (4x4x6=96). You are going to want to replace the air in your grow tent every minute, so you will need an exhaust fan that is rated greater than 96 cubic feet per min or CFM's. VenTech 4" exhaust fan is what I recommend and pulls 190cfm at max speed which is plenty enough to keep a 4'x4' tent exhausted. VenTech offers a complete package with exhaust fan, variable speed controller, and carbon filter. I recommend a carbon filter to scrub the air and remove all smell.
BUY Exhaust Fans, Variable Speed Controllers, and Carbon Filters
Air circulation doesn't need to be complicated or expensive. Simply make sure your grow tent has a good breeze, your cannabis plants enjoy mild movement. Oscillating fans work the best, but if you don't have oscillating fans regular fans will work. Clip on fans are great and you wan to make sure that your fans are not pointed directly at your cannabis plants. While cannabis plants enjoy a fair amount of air circulation, direct wind for an extended period of time can stress and damage them. Air circulation is cheap and a great way to increase the happiness of your cannabis plants.
BUY Air Circulation Fans. Oscillating and Clip On