SAPHIR provides a platform for reproducible studies of the atmospheric degradation of biogenic and anthropogenic trace gases and the build-up of secondary particles and pollutants. SAPHIR is part of the European network of atmospheric chambers EUROCHAMP and provides transnational access. he outdoor chamber is of cylindrical shape (volume: 270m3) and has a shutter system that can be quickly opened and closed to expose the air mixtures to sunlight. The high purity of the air supply and the large volume to surface ratio allows running experiments at low, atmospheric concentrations of trace gases with only minor influences of chamber wall interactions, so that the transformation of trace gases and aerosol can be observed over a long period up to several days. Either artificial trace gas mixtures can be added or emissions from plants that are housed in a separate plant chamber, which air can be transferred into the SAPHIR chamber. The SAPHIR chamber is equipped with a comprehensive, unique set of sensitive instruments for radicals, traces gases, aerosols, and physical parameters. Radicals are detected by differential optical absorption spectrometer (OH), which is worldwide the only absolute measurement device for OH radicals, laser induced fluorescence (LIF-FAGE for OH, HO2, RO2, and OH reactivity) and cavity ring-down spectroscopy (NO3, N2O5). Organic species including oxygenated species are measured by proton-transfer mass spectrometer (PTR-TOF-MS) and gas chromatography. Aerosol properties are characterized by a high resolution aerosol mass spectrometer (WToF-AMS, size resolved chemical composition), CPCs, SMPS and cloud condensation nuclei counter. Inorganic species (NO, NO2, O3, HONO) and also physical parameters are permanently monitored.