The monitoring and control of environmental parameters provide useful information in order to reduce the decay of works of art. Dosimeters that reproduce the pictorial structure of paintings as closely as possible were prepared and tested to evaluate the effects induced on works of art by the "global" indoor environment. These dosimeters were aged under different conditions in ageing chambers, and successively were placed in the Uffizi Gallery for several months. The data obtained from the naturally aged dosimeters were compared with those found for the artificially aged, thus providing information on the alteration process induced by the environmental factors.