Grow Room Air Circulation

by S.C.
(Michigan)

Should circulating fans be on when the light cycle is off? In other words, should they be on all the time?

Answer: S.C.- plants need air circulation for a very different reason than air exhaust. Plants breathe from tiny little holes in the surface of their leaves (mostly on the underside). Plants do not have lungs. Therefore, as plants exhale Oxygen and water vapor, these substances tend to hang in the air, in and around the leaves, choking and suffocating the plants a little. Plus, the high humidity from exhaled water vapor provides excellent conditions for mold and fungus problems.

The solution to all of these grow room problems is good air circulation. Plants tolerate high humidity with fewer problems as long as vigorous air circulation is provided around all of the plants. Air circulation also removes waste Oxygen from around plant tissue and brings it into contact with fresh supplies of Carbon Dioxide (CO2). This exchange is necessary, on a fundamental level, in order to keep plant growth moving forward.

My advice to you is to leave oscillating fans on in the grow room 24 hours a day. One 12 inch fan can provide air circulation to an area of 4' x 8' (so you will not need many to accomplish good air circulation). Also, oscillating fans are much more affordable to run than grow lights or proper exhaust fans (so turning them off is really counter-productive, given the cheap costs). Hope this helps you out S.C., and Happy Growing!