Show returning shrapnel what goes up must come down thus shell fragments from antiaircraft fire fall like hail over the areas from which the shells are fired this is one of the reasons for air raid alarms to clear the streets and surrounding zones of people who might otherwise be injured by the falling fragments according to the U S bureau of standards the average antiaircraft shell is blown into approximately 2500 fragments many of them small and relatively harmless occasionally however large fragments fall with velocity enough to damage buildings and cause serious or even fatal injury to people upon the streets |