http://swrc.ontoware.org/ontology#Article Firn air composition at the H128 and NDFN sites, Dronning Maud Land, East Antarctica en Firn air Antarctica Isotope greenhouse gas nitrogen oxygen noble gas halocarbon ice sheet H128 NDFN Air sampled from polar firn is useful for reconstructing atmospheric composition over the last few decades and understanding the trapping processes of air in the ice sheets, as well as determining the age of air relative to the ice at the same depth. This paper presents the composition of firn air collected at H128 and NDFN in Dronning Maud Land, East Antarctica. The firn air at both sites was carefully sampled using a sampling system developed at the National Institute of Polar Research. We provide elemental and isotopic ratios of N2, O2, Ar, Kr, Xe, and Ne, as well as concentrations of CO2, CH4, N2O, SF6 and CFCs for both sites, measured using high-precision measurement systems across multiple laboratories. The data would be valuable for studying air entrapment processes in firn and reconstructing past ice sheet environments and atmospheric compositions. Polar Data Journal 9 30-43 2025-05 National Institute of Polar Research 2432-6771 https://doi.org/10.17592/001.2024102102|Original Data Atmospheric science/Climatology Glaciology