Historically, a suitable testing protocol to determine the efficiency of in-line grease removal devices designed to remove grease from cooking exhaust streams has been lacking. In addition, there has been a lack of data on the characteristics of grease being emitted from typical appliances when cooking. The primary purpose of ASHRAE RP-851 was to design a testing protocol that could repeatedly determine the collection efficiency of in-line grease removal devices. During the course of the protocol development effort, sufficient data were collected to provide a baseline for determining the grease removal efficiency of several in-line grease removal devices.Units: Dual