The purpose of ventilation is to maintain temps and humidity in the centre of the plant canopy. Generally, it is preferable to have too much ventilation than not enough. Replenishing the air in the room provides more co2 for your plants.
Glandore hydro stocks high quality fans for ventilation in hydroponic grow rooms. Inline, centrifugal, and tube style max fans designed to regulate airflow. Shop fans with built in silencers and speed controllers, oscillating and clip fans. Available in a large range of sizes including small fans for clone tents and propagation. ]