A laboratory ion flow reactor operating under wide ranges of temperatures (213–373 K) and pressures (1–50 hPa) has been set up. This will allow for the potential detection of a variety of atmospheric trace gases to be measured by chemical ionization mass spectrometry. Flow dynamics of the reactor has been characterized in detail in order to extract reliable kinetic data and ion/molecule reactions. Direct comparison between the average ion flow velocity and the carrier gas flow velocity has been achieved experimentally under laminar and turbulent flow conditions. To validate this new setup, the reaction of SF6− ions with SO2 molecules has been studied giving kinetic and mechanistic results in excellent agreement with previous studies conducted at room temperature at low (<2 hPa) and very high pressures (>30 hPa). Consistent data have also been obtained under intermediate pressure conditions and at other temperatures, which definitely establishes SF6− + SO2 as a reference reaction for future fast flow reactor or reaction kinetics validation.