It is well known in the tree care industry that operators can become caught or snagged by material entering a wood chipper. The consequences can be devastating. On commercial wood chippers with mechanical infeed systems, a caught operator can be pulled into the machine by the infeed system. Due to the speed of the infeed system, once an operator has been caught there is a limited window of time before serious injury or death can occur. Commercial wood chippers commonly pull in branches at speeds of 20 inches per second (50.8 centimeters per second) or faster. Therefore, caught operators may have no more than a few seconds to either free themselves from the branches or activate a device to stop the feeding mechanism. As an operator is being pulled into the chipper toward the chipping mechanism, various factors can limit the caught operator’s ability to access or activate a feed-stop device. Consequently, operators are sometimes unable to save themselves from catastrophic injury or death. This paper analyzes the hazards associated with wood chipper accidents and assesses the effectiveness of various safety devices intended to protect operators from this danger. The investigation includes a historical review of wood chipper safety devices and ultimately reveals the importance and effectiveness of feed-stop devices that can be passively activated by an operator who has become caught. The paper addresses commercial wood chippers with mechanical infeed systems.