Ohio Rev. Code § 1567.31: Drill holes.

When a miner drills holes in the face of coal for blasting and such drill hole bottoms in the permanent roof, he shall not charge or fire such drill hole. No miner shall drill a new hole in such a way that any part of it shall be within twelve inches of any part of an unused drill hole or one in which there has been a misfired shot. No miner shall drill out or attempt to drill out the charge or tamping in a misfired shot.