Since there is evidence that air pollution contributes to the decay of objects exposed outdoors to weathering it had to be studied whether air pollution is also effective in the interior of museums and archives. The main difference is that in the interior of buildings there is no liquid aggressive medium exempt from condensation humidity which may play a certain role in temporary heated monuments, like churches. The tarnishing of silver is one obvious example of a corrosive reaction between a gas and a material frequently used for art objects. Theoretically textiles, paper and leather are threatened by air polluting gases, which are accumulated by organic materials. The decision whether acid compounds in these materials derive from the manufacturing process or from the environment normally is difficult. Early paper made from textiles usually has a very low content of acids and is in good condition, while papers from the 19th century, which are very acid and brittle, cannot have obtained all their acidity from the surrounding air. For textiles and paper in museums and archives further research is necessary to find out the contribution of air pollutants to decay. -- AATA