New Grower Needs Help with Ventilation

Hello, I'm new to the grow community. I just set up a grow operation with two seedlings in my closet apartment that is about 2' by 3'. I have put an incredible amount of time into internet research but I cannot find anything on ventilation systems that I'm satisfied with. I don't understand how much air circulation the plants will need if i am fermenting to produce Co2 in the closet. I have a gentle fan on the plants and I'm currently just opening the door every so often to let new air in. I can't sleep at night because I'm so excited! I want to be doing something to help my plants at all times so I do way to much internet research! its ridiculous really

What are the temps

Room temp in SoCal. About 73 degrees, no AC

then a simple fan is fine, nice temp. BTW temp under the light can be way higher than ambient temp