Three years of greenhouse gas measurements, obtained using a gas chromatograph (GC) system located at the Puy de Dôme station at 1465 m a.s.l. in central France, are presented. The GC system was installed in 2010 at Puy de Dôme and was designed for automatic and accurate semicontinuous measurements of atmospheric carbon dioxide, methane, nitrous oxide and sulfur hexafluoride mole fractions. We present in detail the instrumental setup and the calibration strategy, which together allow the GC to reach repeatabilities of 0.1 μmol mol⁻¹, 1.2 nmol mol⁻¹, 0.3 nmol mol⁻¹ and 0.06 pmol mol⁻¹ for CO₂, CH₄, N₂O and SF₆, respectively. The analysis of the 3-year atmospheric time series revealed how the planetary boundary layer height drives the mole fractions observed at a mountain site such as Puy de Dôme where air masses alternate between the planetary boundary layer and the free troposphere. Accurate long-lived greenhouse gas measurements collocated with ²²²Rn measurements as an atmospheric tracer allowed us to determine the CO₂, CH₄ and N₂O emissions in the catchment area of the station. The derived CO₂ surface flux revealed a clear seasonal cycle, with net uptake by plant assimilation in the spring and net emission caused by the biosphere and burning of fossil fuel during the remainder of the year. We calculated a mean annual CO₂ flux of 1310 ± 680 t CO₂ km⁻². The derived CH₄ and N₂O emissions in the station catchment area were 7.0 ± 4.0 t CH₄ km⁻² yr⁻¹ and 1.8 ± 1.0 t N₂O km⁻² yr⁻¹, respectively. Our derived annual CH₄ flux is in agreement with the national French inventory, whereas our derived N₂O flux is 5 times larger than the same inventory.