A blast in a coal mine which--due to improperly placed charges, the wrong kind or quantity of explosives, or insufficient stemming--expends most of its force on the mine air; it sometimes ignites a gas mixture, coal dust, or both, thus causing a secondary explosion, which may or may not spread throughout the mine; a shot that blows out without disturbing the coal; a shot that is not properly directed or loaded; a blown-out shot.