Similarly when works of art are packed under a modified atmosphere, the permeability of the used packaging material used should be considered. In the present study with materials that were not consuming oxygen or significantly emitting gases, a high barrier material which has a very low permeability with respect to all gases was deemed to be suitable in order to keep a constant protective atmosphere within the packaging as long as possible. Changes in the composition of the modified atmosphere are however inevitable. Due to the presence of the modified atmosphere, a gradient in the concentration of one or several gases is created between the atmosphere at the interior and the exterior of the packed work of art.