This paper reports preliminary analysis from a large field study of 100 university classrooms in Central Texas. Lecture classrooms and auditoriums were sampled for three consecutive weekdays in the 2019 – 2020 academic year. Carbon dioxide (CO2) concentrations, used as a marker for both ventilation and exposure, and temperature were measured in the general room area and when able, the supply airstream. HVAC control data that relates to ventilation was also saved for comparison. Preliminary results of typical CO2 concentrations during occupied hours suggest that university classrooms rarely exceed ASHRAE 62.1 recommendations for classrooms. Contrastingly to K-12 classrooms that are often under-ventilated, our data shows that university classrooms are well-ventilated if not over-ventilated. The reason for this over-ventilation is due to non-uniform classroom temporal usage in university buildings resulting in empty classrooms and therefore the variable air volume (VAV) systems, typically found in university buildings, cannot properly adjust ventilation rates.