OH LOL I thought this was about a chickens vent!!! Honestly though, I know nothing about bators, leaning towrds gettign one at some poit though. I just got a kick out of the topic line. I hope you get a real answer quickly.
If you can keep the humidity high enough with it open then do so. More air is good. However if you can't it would be better to close it. I haven't lost one to lack of air flow but I have had plenty of hatching problems due to humidity.
