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Ten Agents of Deterioration

External agents of deterioration include all causes of deterioration or damage that are not derived from the structure of the materials themselves. External threats to collections are often classified into ten categories, known as the Ten Agents of Deterioration.

Physical Forces: Mechanical damage can result from both natural disasters, like earthquakes, hurricanes, and tornadoes, or from human error, such as dropping, marking, or tearing an object.

Poor Security: Theft and vandalism can occur in high risk areas, such as unlocked, unsecured, and unsupervised rooms.

Fire: Fire and smoke cause irreparable damage, usually resulting in a complete loss. Records must be isolated from the risk of smoke or fire, and detection and suppression systems should be in place.

Water: Leaks and floods can also irreparably damage records, causing inks and dyes to run and stain adjacent areas, pages to warp and stick together, and mold to form. Records should not be stored in areas that are prone to leaks and flooding. Never store records directly on the floor.

Pests: Rodents, insects, mold, and fungi are all pests that can destroy collection materials. Pests are attracted to dark, cluttered, damp, and seldom disturbed places. Silverfish, firebrats, booklice, and cockroaches are commonly found in paper-based collections. Mold and fungi can grow on all types of materials, even inorganic objects like plastic.

Pollutants: Particulates and gases contaminate collections through the air or direct contact and may originate from inside or outside a building. Particulates are organic or inorganic materials such as dust, fibers, hair, skin cells, and soot. Particulates can be abrasive, acidic, and attractive to pests. Gases commonly enter a building from the outside environment, originating from the burning of fossil fuels (sulphur dioxide) or traffic exhaust (nitrogen oxides). Ozone is produced both outside and within building environments by photocopiers, laser printers, and electrostatic air cleaners. Common cleaning products, paints, adhesives, and even carpeting contain acids, formaldehyde, and peroxides that are damaging to collection materials.

Light: Natural and artificial light are damaging to all record formats. Damage caused by light is most commonly associated with the fading of dyes and pigments, such as in old photographs. Light also accelerates chemical reactions, interacting with paper and other acidic materials, causing them to darken and become brittle. Deterioration caused by light is cumulative and hard to detect until the damage is sustained, at which point it is irreversible.

Incorrect Temperature: In general, high temperatures accelerate chemical reactions, causing deterioration to occur in all formats. Cooler temperatures are essential to long-term preservation. Fluctuations in temperature also damage records.

Incorrect Relative Humidity: Extremely dry or extremely humid environments damage all record formats. Mold and rust can develop in humid environments while dry environments cause paper, film, and other materials to become brittle. Fluctuations in relative humidity cause materials to expand and contract as they absorb and release water which can lead to mechanical damage.

Poor Handling and Storage: Records are easily damaged through handling and improper storage. Papers are often folded, bent, or rolled. Photographs and negatives sustain damage from oily fingers. Computer tapes, disks, audio cassettes and reels become damaged through over-handling, careless storage, or exposure to magnets or magnetic fields. Incorrect storage furniture and storage enclosures will damage collections if they do not adequately support the materials, causing books to warp, tear, or develop sagging text blocks. Non-archival furniture, enclosures, and storage boxes may be acidic, contributing to chemical deterioration through acid migration.