Sulfides are released from fabric dyes, rubber, wool, silk and felt. The human nose is sensitive to hydrogen sulfide. A rotten egg smell warns us of deadly exposure. Objects are 100 times more sensitive than humans are. Once a molecule of hydrogen sulfide reacts with a molecule of silver or a silver salt in a photographic gelatin layer, that silver molecule is forever changed.
Ozone is a reactive molecule of oxygen atoms.
Many older photocopiers and other electrical equipment generate high indoor levels of ozone. Collections should not be stored or displayed near this electrical equipment. Insecticides and other chemicals. Determining potential damage to a collection is difficult. Many factors impact the rate of damage.