It’s understandable, after you’ve taken the time and care to properly store your bearings, that you would want to be sure to install them in a clean environment. But, that’s tricky. Clean the work bench area and the tools you will use on the new bearing, and keep away any linty clothes. Keep the bearing on its original wrapper or some clean paper when working on it. Don’t let the bearing sit on a dirty surface, even for a short time, or you’ll risk contamination and early failure. And, remember bearings should not be washed, except for oil mist or circulating oil system.