Abstract: On the morning of September 27, 2007, Employee #1, of the Alarcon Bohm Corporation, was working as a laborer cleaning up debris from the ongoing demolition of a mezzanine structure inside a building in South San Francisco, CA. At approximately 7:30 a.m. that same day, a coworker used a reciprocating saw to make a series of cuts from above on the mezzanine floor, releasing one end of a floor support truss section that was about 20 ft long and weighed an estimated 80 to 100 lb. The other end remained connected to a beam above the main floor. The free end of the truss then swung downward about 11 ft to the floor, striking Employee #1 as he was walking under it. The truss landed on his lower right leg, fracturing the tibia and fibula. Employee #1 was transported to Peninsula Hospital, where he underwent surgery on his leg; he was released on September 28, 2007. At the time of the accident, another laborer and an Alarcon foreman were standing nearby. The coworker cutting the trusses free could not be seen by Employee #1, as he had walked about 60 ft from his previous position under the mezzanine to the point where he was struck. Subsequent investigation found that no barricades or warning tapes were in place on the floor areas underneath the mezzanine to prevent workers from walking into the danger zone where the trusses were being removed. In addition, the floor support trusses were being taken down by hand without the use of scaffolding, elevating work platforms or aerial devices for employee safety. The employer was cited for violations of T8CCR 1735(o), Demolishing Buildings: Planks spanning the distance between adequate beams shall be used where necessary as asubstitute for weakened floors, and as access walkways over open or weakened areas. When demolishing floors and roofs, employees shall be prohibited from working below this activity. Demolition of floor spaces shall continue until all unsupported flooring is removed. When employees are required to remove floor support beams, wall sections, etc., by hand, scaffolding as described in Article 21 of the Construction Safety Orders or elevating work platforms and aerial devices as described in Article 24 of the General Industry Safety Orders shall be provided and used where necessary to insure employee safety. The employer was also cited for a violation of T8CCR 1736(f), Disposal of Waste Material: When debris is dropped through holes in the floor without the use of chutes, the area onto which the material is dropped shall be completely enclosed with barricades not less than 42 in. high, and not less than 6 ft back from the projected edge of the opening above. Signs warning of the hazard of falling materials shall be posted at each level. Debris removal shall not be permitted in this lower drop area until debris handling ceases above.