RFID applications have been broadly used in manufacturing fields, such as inventory control and logistics. RFID, which functions like a bar code, provides a unique identifier for objects. The most significant advantage of RFID over the bar code is that it is not a line-of-sight technology over a range of 20 feet. The presence of electromagnetic interference (EMI) can affect tags' detectability and range in manufacturing facilities that have heavy electrical equipment. In this paper we report results from an experimental study of the effect of EMI generated by CNC machining centers typically used in manufacturing facilities on RFID range. These experiments were conducted in a lab at Penn State University, which is equivalent to a medium-sized machine shop. Results show that EMI generated by CNC machines can reduce range of RFID by 20 to 40%. These findings may be useful for designing manufacturing facilities which use RFID.