Abstract: At approximately 8:30 a.m. on October 24, 2012, Employee #1 was working as a maintenance worker for the Pleasanton Unified School District, in Pleasanton, CA. Employee #1 was a skilled maintenance worker who had worked for his employer for almost 22 years. Employee #1 also performed HVAC maintenance and troubleshooting, which had been his main duty for 10 years. On the day of the incident, Employee #1 was assigned by the lead maintenance person to check the HVAC on the rooftop of the Independent Study Building. The HVAC equipment was located just above the maintenance department office. Employee #1 used a ladder to access the rooftop from the north side of the building. Employee #1 was later joined on the roof top by a coworker using the same ladder for his access. After troubleshooting the HVAC, they found that they needed a gas valve. Both decided to go down from the roof to get the needed material. The coworker went ahead, followed by Employee #1. While Employee #1 was descending the ladder, the ladder slipped out from under him. He fell, and his left foot became entangled with a ladder rung. In the fall, he sustained a fracture to his left leg. Employee #1 was taken to the Valley Care Hospital in Pleasanton, where he was hospitalized for 28 hours. The incident was reported by the employer's human resources manager to the Cal/OSHA Oakland District office at 3 p.m. on the same day.