I have a Hova-Bator which has two vent plugs. I downloaded the manual from the GQF website. It tell the reason for the vent plugs and how to use them for your application. It doesn't say anything about removing them for oxygen, they are for controlling humidity. Simply, if the humidity gets too high during the hatch remove the plugs etc. If your incubator manufacturer has a website they should also be able to supply you with a pdf format instruction manual you can download and print out with instructions on when to take the plugs out or leave them in.