The investment casting environment poses many health risks to workers, including exposure to respirable crystalline silica. The Occupational Safety and Health Administration (OSHA) issued a new final comprehensive rule in 2016 that lowered the Permissible Exposure Limit (PEL) of respirable crystalline silica to 50μg/m3 for any combination of quartz, cristobalite, or tridymite. Washington State issued a similar respirable crystalline silica rule (WAC 296-840) but combined construction and general industry requirements into one rule with the permissible exposure limit of crystalline silica at 50μg/m3 as well. This rule is intended to decrease the incidence health effects associated with respirable crystalline silica exposure such as lung cancer, silicosis, chronic obstructive pulmonary disease, and kidney disease. (IARC, 1997) At a local investment casting foundry, workers are exposed to respirable crystalline silica during the knock-off operation, where the shell is knocked-off the recently cast metal part. The goal of this project is to design, construct, and evaluate the effectiveness of engineering controls in the form of a local exhaust ventilation system on worker exposure to respirable crystalline silica during the knock-off operation. Air sampling consisted of real-time, direct reading instrumentation for the respirable fraction of dust and full shift total dust and respirable fraction personal samples from the breathing zone for crystalline silica. Air samples were taken before the construction of the local exhaust ventilation system and combined with historical data to establish a baseline of worker exposure to crystalline silica. After the local exhaust ventilation system was designed and built, there were two rounds of air samples collected with methods identical to pre-control air sampling. The results were analyzed to assess how effective the local exhaust ventilation system is at lowering worker exposure to respirable crystalline silica. As an administrative control, and in accordance with the new respirable crystalline silica final rule, an exposure control plan was drafted and implemented at the foundry. The results indicate that the local exhaust ventilation system is an effective means of lowering worker exposure to respirable dust and respirable crystalline silica.