Temperature is controlled by facilities and should stay as cool as possible. If you find your areas feeling warm, contact both preservation and facilities.
Temperatures above 72F should be avoided in any area where books and paper items are. Temperatures above 76F should be especially avoided. A reduction of temperature from 70F to 40F will extend the life of alkaline paper by a factor of 500 times and of acidic paper by a factor of 1000 times. Adverse chemical reactions are halved with every 18F decrease in temperature.
Mold and pests will also decrease as temperatures go down. Insect populations are more easily controlled when temperatures are kept below 68F.
Extreme swings in temperature are more harmful than high temperatures. Temperature should not vary more than +/- 5F in any 24-hour period. For this reason, avoid placing materials close to outside doors. Exhibition areas near outside doors should only contain facsimiles of items rather than the items themselves--see section Exhibition of Items.
Relative Humidity is the amount of water the air can hold without reaching the Dew Point (Condensation). Relative Humidity changes with temperature as warmer air can hold more water. The warmer your areas are, the more damp your air can become and this will cause damage. For this reason, temperature and humidity go hand in hand so it is important to understand the differences as well as their relationship with each other.
Humidity is controlled by facilities and should stay as dry as possible. If you find your areas feeling humid, contact both preservation and facilities.
Avoid any RH that is <25% or >50%. Low RH can embrittle pages and leather, causing cracking and internal damage. High RH will cause excess mold growth and attract insects.
Extreme swings in humidity are more harmful than high temperatures. Humidity should not vary more than +/- 5RH in any 24-hour period. For this reason, avoid placing materials close to outside doors. Exhibition areas near outside doors should only contain facsimiles of items rather than the items themselves--see section Exhibition of Items
Do not block air vents or grills--air flow is extremely important to relative humidity.
Plants can cause RH issues around collection materials--see the section on Plants in Offices and Collection areas for more information.
Dew Point is the temperature at which relative humidity is 100%; meaning, at the point at which water vapor turns to liquid. The warmer the temperature, the higher the dew point as warmer temperatures can hold more water vapor in the air.
This is noticeable inside by condensation. To prevent condensation, ensure that windows, doors, openings around pipes, cracks, ,etc. are sealed. Reduce water resources by controlling leaks and watching for condensation on pipes. If any of these are a problem in your area, contact facilities and preservation.
Monitoring dew point is a good way of determining how good your building envelope is. If your dew point average is slowly climbing, it means your HVAC cooling system is slowly failing. A sudden dew point spike usually is an indicator of bad weather, like hurricanes. Preservation and facilities should carefully monitor dew point as a means of ensuring their HVAC systems are repaired before fully breaking.
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