I would still have some sort of air exchange going on. If the tent is closed up and only circulating the air contained within it'll will, eventually, deplete the CO² and slow, if not stop, photosynthesis. So, yes, air exchange of some sort. Be it passive with the vents or an unzipped bottom of the door, or assisted intake, you need one or the other for healthy plants. Do you Need an intake fan? In A tent 5x5 and under i can't see the benefit. A properly sized exhaust fan will provide plenty of fresh air to your plantsIf I don’t have air sucking out of tent or blowing in is that fine @Johiem