Depending on the size of the room and the amount of refrigerant in the largest circuit you may need to treat the room as a machine room which dictates exhaust rates and operation. Refer ASHRAE 15.
The size of your fan will be dictated by the heat generated by the compressor during operation , does this room have just one compressor, or are there several. If so do they all operate at the same time?
B.E.
You are judged not by what you know, but by what you can do.
One of the plants that I worked for was involved in heavy structural steel. There were several air compressors and the heat generated was released to the manufacturing areas. You have to do the math to determine the range of temperatures you want to maintain in that room and the size of the air louvers can be based on guidelines provided by the NFPA. I don't believe that the NFPA has any guidline for air compressor room but you'll find guidelines for intake air louvers in topics such as boiler rooms. Also peruse the OSHA 1910 general industry standards for similar information.
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.
Thanks all who comments here. According to your comments and theories that I found on the internet, I found that the optimum solution is putting louvers for both supply side and exhaust side. It is much needed to control the room temperature which is very high at the moment.
I don't know the number of compressors in the room in question, but as a cautionary measure sound levels could increase substantial in the work areas by installing air louvers.
