Abstract: On July 7, 2010, Employee #1, an Excavator Operator of J.F. Shea Construction, Incorporated Dba Aggregate Products, was working alone operating a WA600 Komatsu front loader and feeding the overland (2.5 miles of a conveyor system which feeds the screening plant) with raw material. Employee #1 turned on the air conditioning unit, which began to spray out liquid and vapor from the vents and sides, spraying him in the face within the enclosed cab. He turned off the air conditioning unit and throughout the day Employee #1 attempted to get the air conditioning unit working correctly while still feeding the overland. In the afternoon, Employee #1 drove back to the plant and informed his supervisor of the events and then headed home. On July 8, 2010, Employee #1 called in sick and on the next morning, he drove himself to the hospital, where he was later admitted for treatment for reactive pneumonitis from exposure to R134A (1,1,1,2-tetrafluoroethane).