Proper ammunition storage is an important safety consideration both in the home and in defense operations. Ammunition for most weapons ranging in size from .22 caliber bullets to GPS guided missiles consists of an explosive charge somewhere in the design. The charge can be used as propellant or payload, but in either case can explode if stored improperly and damage nearby equipment and structures.
Ammunition storage systems must fulfill several important functions. Ammunition must be kept dry, because many explosive propellants and charges cannot function effectively when wet. Stored ammunition must also be kept in a temperature controlled environment, because many explosive compounds deteriorate when the temperature is too low, and can spontaneously ignite if temperatures are too high. Ammunition storage must also take into consideration other environmental factors like the rusting of ammunition casings and the movement of storage containers in event of an earthquake or other disaster.
Ammunition is typically best stored in a metal container that seals to be airtight. The container should be secured if stacked with heavier containers on the bottom of a stack. Many military surplus stores sell old military ammunition containers, often called ammo cans. These can be filled with cardboard boxes identifying the type of ammunition stored within, and then stacked easily in a dark room - ideally a heavy safe. This will prevent a home ammunition storage unit from being stolen in a burglary.
On a larger scale, military ammunition storage procedures are similar, only undertaken on a larger scale. Ammunition is often produced en masse during times of crisis or conflict, and after the immediate threat is passed the investment in productive resources used to build ammunition will be wasted if the ammunition is merely sold or scrapped. Many nations have taken to storing ammunition in large, well secured dumps - military bases with restricted access and covered in hardened bunkers to prevent unauthorized removal of ammunition.
Storage of ammunition and other old military equipment was extremely common in the Soviet Union, which built huge ammunition storage facilities where equipment and ammunition going back to the Second World War were kept in reserve in case of dire need. However, the experience in 2003 Iraq offers provides a cautionary tale: ammunition storage facilities not properly secured can result in theft of military grade equipment by the public at large, which can lead to major public safety problems.