The proper control and distribution of ventilation air is a key aspect in the productivity of an underground mining operation and is crucial to the health and safety of mine workers. Accurate measurement of air velocity is an essential component in achieving effective ventilation planning and control. However, the measurement methodology and application is problematic, especially in the use of correction factors. This paper examines the accuracy of these factors as they are affected by measurement location, instrument, and flow characteristics. Definitive recommendations are presented to improve the accuracy of flowrate determinations.