My preserved garlic seems to be fermenting

Does anybody know if this is normal?

About a month ago I preserved garlic in olive oil and put it in the refrigerator for quick and easy use as needed. No I have noticed that there is pressure underneath the lid when I take the glass out of the refrigerator. I have not noticed a bad smell or taste, but I do wonder if this is normal and for how long will the garlic be usable?

We will see.