When nightmare has reached your artworks

There’s a lot you’ve got to do in your life, works to be done, searching fun for life. You are busy and sometimes forget what you have in the art storeroom. One day, you found some weird stain or dirty mark appear on your precious art, some paper changes its color. You find out that it is mold, which can do enough damage. To left untreated, the mold can spread more. Let’s get to know them better to find the protection before your priceless works will be destroyed by mold. What are the causes of that?