1. Air Circulation
Along with humidity and temperature control, adequate air circulation will help prevent mould growth. Air circulation helps control moisture levels through evaporation.
2. Temperature
Most moulds thrive in warmer temperatures. Temperatures below freezing will not kill mould, but will inhibit their growth.
3. Humidity
Generally, it is recommended that relative humidity remain at 50% with a max. change of plus or minus 5% per month.
4. Light
Sunlight, and in particular UV radiation, generally retards mould growth. Sunlight and ultra-violet radiation, however, cause serious fading of library materials and can speed up chemical reactions leading to the formation of acids in paper therefore is not recommended.
5. Chemical composition

Mould growth can also be affected by the chemical composition of the book or paper food source. Many fungi prefer slightly acidic material.