Abstract: At about 9:00 a.m. on February 3, 2005, Employee #1, a source testing engineer with Airx Testing, was setting up equipment on the roof of a building to check an exhaust pipe as part of Airx's contract to test smoke stacks for AQMD (air quality management district) compliance. He was at the Maruzen of America facility. As Employee #1 was descending a 20-foot metal extension ladder, the ladder slipped off the slightly sloped surface on which it was positioned, and Employee #1 fell approximately 13 feet onto a paved floor. He landed on his left side, sustaining a fracture of the left pelvis, a sacral fracture, and a fracture of the left wrist. 911 was called, and the paramedics arrived and transported Employee #1 to Harbor UCLA Medical Center, where he was admitted. After one week, he was transferred to Ventura Community Hospital, where he stayed another week as an inpatient. The causal factor of the accident was that the ladder slid off the surface, but it is not clear whether the ladder slipped because of the slope or because of a worn out rubber pad observed on one of the ladder's footings. Employee #1 was a permanent employee of Airx with 20 years of experience working in the trade.