To reduce this risk, the oil should be refrigerated and used within one week.

http://en.wikipedia.org/wiki/Garlic

To reduce this risk, the oil should be refrigerated and used within one week. According to wikihow, the garlic immersed in oil should be stored in the freezer and not the fridge.Commercially prepared oils are widely available. Manufacturers add acids and/or other chemicals to eliminate the risk of botulism in their products.Two outbreaks of botulism related to garlic stored in oil have been reported.

Garlic bulbs should be clean and white with a dried neck and outer skin and quite firm under pressure. They should be discarded if they are soft or spongy or show signs of mould.