How large is the space? What size light are you running, and what size (cfm) fan are you running?

I have used one fan to air cool a 400 watt and run a carbon scrubber to exhaust the space successfully before if that is your question. I was advised by the people selling it to me that you couldn't run them off the same fan, and I did it in spite of that. It was able to keep a steady temperature around 80 indoors during the summer, so I felt it was a success.

We need a little more information to accurately fill in the blanks for you.