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Aerial emissions from animal feeding operations have been a growing concern for rural residents in the U.S. In order to accurately quantify emissions from a livestock facility, the ventilation rates of each fan operating at a facility are needed. One means of providing this information is to create an in-situ calibration for each fan. The original Fans Assessment Numeration System (FANS) was developed for this purpose. Since the first generation FANS units were released major improvements have been made to improve their efficiency and reliability. The purpose of this paper is to outline the new enhancements made to the fourth generation (G4) FANS units and compare the performance of the fourth generation to its predecessors. The most recent updates included a faster travel rate, sealed limit switches, and an adjustable chain tensioning mechanism. In addition to the hardware updates on each of the new units, the FANS software was updated to include Bluetooth wireless connection capabilities, real-time anemometer RPM and estimated ventilation rate readouts. Four newly manufactured G4 FANS units were calibrated and compared to previous generations of the FANS units. A calibration drift assessment was also performed on select individual FANS units over a ten-year period, which found the absolute accuracy of the FANS units do not fluctuate over time unless there are mechanical malfunctions occurring within the FANS device.