HELIOS is equipped with a large set of instrumentation: in-situ FTIR (up to 500 m path length), PTR-ToF-MS (Ionicon 8000), Aerodyne ToF-CIMS, ATD-GC-MS, UHPLC, IC, SMPS, LOPAP (for HONO), Aerolaser 4021 (for HCHO), Spectroradiometer, Monitors (O3, NOx (NO + NO2), SO2), CRDS (NO3 & N2O5) …. Other instruments are under development.