Well without pictures its a little more difficult to take a good guess, you need to figure out the dimentions of your grow space.

First you need to find the cubic volume, multiply (in feet) L x W x H. Since all exhaust fans are rated in CFM (Cubic Feet per Minute), all you need to do is take the cubic feet and multiply it by three, then find a fan rated slightly higher than the number you got.

EXAMPLE: a 70 CFM fan would be adequate for a 35 cubic foot area (35 x 3 = 105 cubic feet), and would be ideal for a 23 cubic foot area. (23 x 3 = 69)

REMEMBER!! you want your plants to have circulation, NOT to have a hurricane going through.

Hope this helps

- mike :smokin:
biff Reviewed by biff on . How Many CFMs do I want? Im planning to use a 150 watt HPS lamp in a 3ft x 1.5 ft x 3ft enclosure with two plants in a scrog setup. I want to have two fans running; one to get rid of the heat that the light creates and another to bring in fresh air from outside the cabinet. I will have ducting up to the lamp for the exhaust and ducting pointed at the plants for the fresh air intake. I plan to use small AC or DC computer type fans but Im clueless as to how many CFMs per fan I should get. I was considering buying some Rating: 5