One of the main purposes of regular cleaning in museums is to control dust. Dust comprises matter from both the outside and inside environment. Dirt, soil, soot and salt enter the building from the natural environment, while the most common matter to collect indoors is human skin and hair. Dust is potentially damaging to collection items. A film of dust over everything also suggests neglect.

Dust

• builds up quickly
• absorbs moisture so can create a humid environment in a small, confined area
• can be gritty and therefore abrasive when rubbed from an object
• attracts and harbours pests
• can absorb and carry pollutants
• can cause staining
• can collect in pockets and cause physical damage to objects through distorting
• their shape and causing cracks.

A bit more on dust from the British Library collections care blog.