AN EVALUATION OF A LOCAL EXHAUST VENTILATION CONTROL-SYSTEM FOR A FOUNDRY CASTING-CLEANING OPERATION

A study was conducted to evaluate the effectiveness of a local exhaust ventilation system for a foundry casting-cleaning operation in which a worker cleaned gray iron castings using a variety of handheld chippi ng and grinding tools. The operation originally had an exhaust system consisting only of an exhaust duct terminating approximately 1 m (3 ft ) above the floor and 2 m (6 ft) from the casting-cleaning workstation . An earlier evaluation of this original control system found time-wei ght ed average exposures to respirable silica ranging from 124 to 160 mu g/m(3). The local exhaust Ventilation system evaluated in this pres ent study consisted of a downdraft booth outfitted with a turntable fa r manipulating the castings. The modified local exhaust ventilation sy stem was installed at this facility and connected to the existing plan t exhaust ventilation system through the original ductwork. A direct-r eading instrument was used to measure the operator's respirable aeroso l exposure concentrations during a single day both before and after th e installation of the new workstation. The same worker was sampled bot h times. The operator's activities were recorded on videotape so that the exposures associated with the various tools could be determined. W hile day-to-day variability could not be accounted far, depending an t he type of tool used the local exhaust ventilation system reduced expo sures by 59 to 79% during casting cleaning by the sampled worker when compared with the original configuration. These reductions were statis tically significant.