text: As area denial weapons do not discriminate between friend, foe, or civilian, they make the affected zone hazardous for all trying to enter. Concepts for area denial weapons which do discriminate (by active sensing) have often been proposed, but have not yet reached a stage of general usefulness, due to their high complexity (and cost) and the risk of misidentification.
  Explosive-based area-denial weapons (mines) may be intentionally equipped with detonators which degrade over time, either exploding them or rendering them relatively harmless. Even in these cases, unexploded munitions often pose significant risk.