In general, moisture, darkness, and poor air circulation are ideal conditions for mould growth. Warmth is a factor, but certain moulds and bacteria will thrive in cold temperatures too. Mould can weaken, stain, disfigure and have a detrimental effect on all types of library material. Pests Insects feed on organic substances such as paper, glues, gelatine sizing, leather, and bookcloth. They prefer warm, dark, damp, dirty, and poorly ventilated conditions.
Bird nests are also a major source of food for insects.
Pollution Gaseous pollutants such as sulphur dioxide, hydrogen sulphide, nitrogen dioxide, and ozone combine with moisture in the air to form acids that attack and damage library material. Particulate pollutants such as soot, dirt and dust, abrade, soil, and disfigure materials. Dust and dirt that have absorbed gaseous pollutants from the air and settled on library material become sites for harmful chemical reactions. Particulates can also aid mould growth. Modern library material such as magnetic and optical media are very sensitive to dust and dirt.