The Damage Alert System is a patented vibration-activated alert system for wood grinders. Units sense unwanted metal objects that enter the wood grinder, and prevent severe damage by shutting down. This system allows users to avoid the need to look through debris by hand or listen for loud noises that would alert them to trouble in the mill, and can be operated with one or two sensors depending on the necessary level of protection. Sensitivity can be adjusted to control the size of metal objects permitted through the grinder, and units can be mounted quickly anywhere on a machine.