Help with airflow.

I have a grow box, 1.75Ft(H)x3Ft(W)
It will be a LST grow.
It currently has 1 17'' florescent tube light. There is a whole at the bottom i use for cords but also it is the air intake whole. Now I have a computer fan which I would like to use as an exhaust. Right now it is just in the box circulating air, does this do anything? will an exhaust help with the quality/quantity of my grow?

Should I make the fan an exhaust or have it just circulate air?

Smell is not a problem.

By placing the exhaust fan at the top and the intake at the bottom each on opposite sides you will have air circulation. An exhaust may lower your temps if it is able to move enough air.