Books, paper and other items in library and archival collections require strict environmental controls to slow the rate of their deterioration. The effects of temperature are discussed and recommendations are given for appropriate levels which should remain constant. Relative humidity levels are also recommended. Paper requires a certain amount of humidity to retain its flexibility, however the levels should be low enough to slow deterioration and control insects and mold. Film and photographic media may require lower levels of humidity and mixed media objects require compromises. The level of relative humidity in the building should cause no structural harm to the building due to condensation in cold weather. Good air circulation and non- electrostatic gaseous pollutant filters will keep pollutant levels down. The ultraviolet content of light sources should be less than 74 microwatts per lumen. Daylight should be avoided, fluorescent bulbs should be filtered and reflected light could be used.