Abstract: At 2:00 a.m. on March 15, 2012, an employee and a coworker were retrofitting the HVAC system with a new variable air volume (VAV) control box with electrical controls. The employee accessed the air unit that was located above a drop down ceiling. The employee was working alone on the 25th floor of the building atop of a frame ladder. While installing VAV boxes to the HVAC unit, the employee followed the protocol in place in which the local electrical interrupter (switch) located on the HVAC unit was used to de-energize the unit. The switch shut off power to the unit, however, there was a 277 volt line coming into the switch. The employee contacted the live electrical parts and was electrocuted. He fell from his ladder onto the ground of the 25th floor. At 2:05 a.m., the coworker returned to the 25th floor to find the employee lying on the floor next to the ladder and unresponsive. The coworker called the emergency medical services and the employee was transported to a local hospital. The employee was killed by an electric shock.