I'm fermenting my first batch of beer in my fermenter which is a food grade plastic pail. This pail does not have a fermentation lock (airlock) on it's lid. I noticed today when i was checking on the brew that the lid is starting to rise or bubble in the center, as there is no way for the carbon monoxide to escape because i closed (snapped) the lid tight. Should i just lay the cover on top of the pail without snapping it shut so the carbon monoxide can escape or will that give me bacteria???