If you are asking if you need one or two fans the answer is it depends.
It will depend on how you are managing air through the compressor room. If you are going to duct the air in/out you may need 2 fans. If you are using louvers or a roof vent, a single fan on inlet/outlet is usually sufficient. The key is sizing/selecting a fan with enough ESP to overcome losses through louvers and/or ductwork.
If my understanding of your setup is correct, common practise is to use a single exhaust fan, make-up air via louvers with either motorized or gravity dampers. Use of a single fan is cheaper up front costs and uses less operational energy (smaller utility bills).
If you are in a humid environment you may want to consider a 100% OA unit on the supply side with exhaust louvers.
The correct answer to your question is the solution that meets Code requirements and is Life Cycle Cost Effective.