Contamination is a leadinc cause of motor bearing failures in electric motors. Regularly cleaning and maintaining the electric motor is the best way to avoid contamination, which can occur from many sources. Contamination happens when foreign substances work their way into cleaning solutions or bearing lubricants. Dust, dirt, abrasive materials, and small particles of metal, such as steel, can find their way into the electric motor from other machinery, contaminated tools, or if the motor is handled by technicians with dirty hands. Denting in the raceways and rolling elements and vibrations indicate motor bearing failure due to contamination.