Do I need a fan in my furnace room?
Why do you want to add a fan would be my question. Most new systems are sealed fire boxes with intake and exhaust being piped directly outside. If the old system that was possibly an open combustion chamber worked why do you think it needs to be changed? Look for 2 large pipes usually plastic 2-3" connecting to the furnace, if you have these they are your intake and exhaust. In my area these are required to be vented outside the home. + isserwood comment I agree.