An indoor evacuable environmental chamber has been built at Lisa. The photoreactor is made of Pyrex tube and is equipped with an irradiation device to study photochemical reactions in the UV and visible ranges. A UV-visible DOAS and a long-path FT-IR spectrometry device have been designed to perform analyses of trace components of reactional mixtures during atmospheric simulation experiments. These facilities are unique in France and new developments have been designed and performed in the analytical device to allow a very long path and high stability of the optical path. The entire apparatus is described and the results of calibration experiments are given.