Hey James my opinion is that its extremely important to have air moving via fans my grow space is small 4x5 and I have 3 fans one small one underneath the canopy at ground level about 12" off the floor I like to keep air moving by the pots there in keeps mold from happening another fan about 12" above the canopy not directly on the plants but they all have a light shake to them this strengthens the stems and keeps fresh air over your plants. If you put fan directly on them you will give them wind burn.