In the last decade, fungal infestations have emerged in Danish museum repositories challenging cultural heritage preservation. The growth is unexpected as the relative humidity in most repositories is controlled according to the international guidelines for heritage collections. This pilot study examined three museum repositories with the aim to enlighten inexplicable fungal infestations. The study showed growth of A. halophilicus, A. domesticus, A. vitricola and A. magnivesiculatus; four xerophilic fungi which are able to grow on substrates with low water activity and may be associated with a revision of the environmental guidelines for heritage collections. Larger studies of the prevalence of xerophilic fungi can give a more comprehensive understanding of the causative factors and improve preventive conservation of heritage collections.