Items in the rare collections are housed in one of three vaults: one for materials from before 1870, mostly of paper made from rags; another for pamphlet and newspaper volumes; and a third for rare items from after 1870. In addition to being cooled to around 45 degrees, humidity is controlled, and air filters are used to remove mold spores and other matter. The rooms are kept in darkness, except when there is a visitor, in which case particular lights are used.