First real time CO2 and O2 measurements on the High Altitude Research Station Jungfraujoch (Switzerland) are compared with corresponding flasks samples. Whereas CO2 measurements show a good agreement, O2 compares only moderately. Real time O2 measurements are performed using two different methods, i.e. by paramagnetic and fuel cells. Fuel cell values exhibit significantly higher scatter, but they compare acceptably well with the paramagnetic values when averaging over 228 min (20 point running mean). Continuous measurements are powerful in many respects in contrast to spot-like flask sampling. They help to set up data selection criteria and to improve the robustness of trend calculations. Further, real time measurements help to partition the anthropogenic CO2 increase into ocean and terrestrial biosphere for short-time variations of minutes, hours, days, which are not covered by flask sampling.