FM 6-30 Chapter 4 Call For Fire (CFF)
"DANGER CLOSE is included in the method of engagement when the target is (rounds will impact) within 600 meters of friendly troops for mortar and artillery, 750 meters for naval guns 5-inch and smaller, and 1,000 meters for naval guns larger than 5-inch. For naval 16-inch ICM, danger close is 2,000 meters. "
Suomalaisten oppaiden mukaan lyhyin varmuusetäisyys 155 mm taitaa olla 300 m (100+200 sirpale-etäisyys) ja tietyissä tilanteissa se voi olla reilusti yli 1000 m.
Danger close on eri asia kuin varmuusetäisyys eli RED, risk estimated distance.