The fan is an just an inline duct fan. They may also be known as squirrel cage fans, but im not sure. They are a common type, generally used in bathrooms for extraction i believe. The fan is sucking air out, through the filter and light. My tent is in a room with the windows open, and air comes in from vents (holes) in the bottom of the tent. The only other thing i have is a fan to blow the plants a little.
Im not sure what you mean about optional air intake fans? What you see is all i use.