Oscillating fans are almost mandatory for all grow rooms. This is because constant air circulation in the grow room is needed for multiple reasons. First, moving the air within the grow room helps to make sure the temperature and relative humidity is consistent throughout your environment, not allowing for hot or cold spots that could negatively affect growth rates of your plants.
Secondly, gently moving your plants with air is a good thing! It's not going to harm your plants, and it will actually make them much stronger. Just like humans develop calluses on their skin, plants develop stiff and strong stems and branches from continued movement.
Lastly, pests and molds do not like a lot of air movement. Making your plants a voltatile place for these non desireables to set up shop will save you anguish and yield!
There's no formula for exactly how many oscillating fans you need based on square feet of your growing environment. Our recommendation is to use one 16" wall mount fan for a 5' x 5' size grow area or larger. Usually we recommend two oscillating fans for a grow room 8' x 8' or larger.
If you're growing in a commercial grow room (e.g., a room larger than 10' x 10') then we recommend putting a wall mount fan approximately every 10' along the perimiter walls of the grow room.