Abstract: On May 5, 2010, Employee #1, an experienced stationary engineer, was performing preventive maintenance on an air handler unit (AHU) on the north side of the sixth floor penthouse (AHU- N6) at the UCSF (University of California, San Francisco) Mission Bay Facility. Employee #1 followed the lockout/tagout procedure for the air handling units, which consisted of contacting the watch engineer at Building Maintenance Service (BMS) on the first floor (Control Center) to turn off the "override command" of the VFD (Variable Frequency Drive) located next to the AHU-N6 at the sixth floor penthouse. Employee #1 then disconnected power to the VFD unit, locked it, and tagged it. He was working on the supply air fan, which had five 0.75-inch ribbed-ridge V-belts. Employee #1 determined that the belts needed to be replaced. At approximately 10:00 a.m., he had completed changing all five belts and was adjusting their tension. Before Employee #1 restarted the unit, he visually checked belt movement by manually moving the belts. He noted that one of the inner belts was flopping. Employee #1 picked the flopping belt with his right thumb and index finger and pulled it down to ensure it was properly situated in the groove of the small sheave (pulley). However, he failed to remove his fingers from the belt in time, which caused his middle finger to be pinched between the belt and the sheave. The tip of Employee #1's finger was severed. A coworker transported Employee #1 to the hospital, but the severed tip could not be reattached. Because the lockout/tagout procedure had been followed, the employer was not cited for any accident-related violations. The employer argued that adjusting belt tension did not require moving the flywheel and that it was Employee #1's decision to do so, prior to restarting the motor. Moreover, use of extension tools was not feasible for this procedure.