Storing materials under appropriate environmental conditions to protect against inappropriate temperature and humidity, excessive light, dust, insects and air pollution is a very important part of a preservation program. The National Diet Library uses means such as maintaining stacks at 22 degrees Celcius and about 55% relative humidity, installing automatic lighting devices, etc.

Reference: Preservation Environment of Stacks and Anti-disaster Measures in Japan
Toshiko Kenjo. Preparing for preservation environment: against severe climate and various disasters: Proceedings of the 7^th Annual Symposium on Preservation, National Diet Library, Japan Library Association, 1997

The stacks of the Annex are entirely underground, from the first basement to the eighth basement.

Discharge nozzle of halogenated agent fire extinguishing system and the central control room.