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 about 22 degrees Celsius and about 55% relative humidity, installing automatic lighting devices, etc.

	The stacks of the Annex of Tokyo main library are entirely underground, from the first basement to the eighth basement. Stacks underground are not susceptible to extreme fluctuations of temperature outside and are quake-resistant.
	Rare book stack(wooden) in stacks
	Stacks of the NDL - Rare Book Stack (National Diet Library Newsletter No. 172, Apr. 2010)

	Storage area of microfilm at 18 degree Celcius and 25% relative humidity

Various boxes, various enclosures