As mold destroys paper the books are frozen until they can be dried.
This process will damage the book but not destroy it and the information will be intact.
The library was burned down, it contained over 20,000 manuscripts with only a fraction of them having been scanned as of January 2013.
Library fires have happened sporadically through the centuries: notable examples are the destruction of the Library of Alexandria, destruction of Library of Nalanda in India and the accidental burning of the Duchess Anna Amalia Library in Weimar.
Causes vary from arson to the sun's rays setting fire to leaflets through the action of a magnifying lens, as happened to a library in Northam, Devon.
Before the Congressional Accountability Act of 1995, the Library of Congress and all Capitol Hill buildings were exempt from safety regulations.
After the Compliance Office inspection, however, the LC announced their wholehearted commitment "to achieving the highest level of safety possible" and "the Architect of the Capitol and Library of Congress will report their progress to the Office of Compliance every three months".
This standard is called NFPA 75 Protection of Information Technology Equipment.