Abstract: At 8:30 a.m. on August 12, 2012, an employee was installing an elevator or escalator at a construction site in Chicago, Illinois. A two-story, 6.1 meter-tall (20 foot-tall) building was undergoing alteration or rehabilitation. At the time of the incident, a Stihl TS420 gas-powered cut-off machine was in use. The Stihl TS420 cut-off machine is designed for cutting steel and concrete only. The employee's employer had fitted the machine with a 300-millimter (12-inch), 20-tooth carbide tip woodcutting blade. The instruction manual issued by Stihl (the cut-off machines manufacturer), warns against using the Stihl TS420 for cutting wood of any type, due to the risk of kickback that can result in serious physical harm or death. The machine was being used to cut off the top sections of 75-millimeter by 200-millimeter (3-inch by 8-inch) oak timber shoring in an elevator pit. The machine was being operated at chest level. The machines rotating blade kicked back a piece of wood. The wood struck the employee in the chest. The employee sustained chest lacerations and was hospitalized for his injuries.