The goal of preventive conservation is to provide the correct maintenance of our cultural heritage in order to enrich our future. The Canadian Museum of Nature developed a risk model for preventive conservation that has proven useful in application to a Portuguese archive. This work applies this model to compare the magnitudes of specific risks estimated for this same archive collection when located in either of two pairs of storage rooms. These rooms are in two different parts of this building: two are in an older part and two are in a recent addition. It was, therefore, necessary to assess the building itself, both structurally and environmentally, as well as analyse its common human practices. In terms of the overall risk magnitude, the best room was found to be in the recent building and the worst in the older building. However, risks related to water problems were found to be higher in the new building. In this work cost-free measures and easy to implement recommendations are given in order to improve the quality of the storage rooms. A final comment on the method itself is also given. (C) 2009 Elsevier Masson SAS. All rights reserved.