The corrosion of materials by the combined attack of different air pollutants is a complicated process, as their total influence must be considered as a combinatorial one rather than a simple summing up of the isolated effects. Corrosion testing in an artificially polluted atmosphere should hence take into account as many parameters as possible to simulate an urban environment in a realistic way. Up to now, most laboratory corrosion tests have been performed in atmospheres enriched in SO₂, or in concentrated sulphatic solutions. Therefore, the development of a more complex artificial weathering system seemed to be necessary to produce corrosion effects similar to those found in an urban atmosphere. As the knowledge of the nature and the range of concentration of the relevant pollutants present in an industrial atmosphere is essential, a review is given which shows that corrosive components are acting as gases and aerosols beside their solution in rainwater and that their concentration in condensing phases like hoarfrost or haze may be many times higher than in the atmosphere under normal conditions. The weathering apparatus presented by the authors was constructed in order to produce simultaneously both gases and aerosols of acidic and/or oxidizing nature for testing different kinds of material. Besides, meteorological events such as changes in temperature, relative humidity and wind turbulence as well as UV-radiation can be simulated. The paper gives a description of the capacity of the apparatus and its individual parts.