If you mean the plastic humidity dome that fits on top of the seedling tray, yeah those are mostly there to hold in the humidity. On the plus side, holding in that extra moisture means that you don't have to water the trays as often. On the negative side, it can promote damping off if you don't remove the cover once the seedlings start sprouting.
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I find humidity domes to be unnecessary for peppers, as long as you don't let the cells start drying out. In fact, I stopped using humidity domes completely after my first season. My pepper seeds germinate very well without them. So, I wouldn't hesitate to remove the domes if you feel the need to.