21.—(1) No person shall charge a shot hole unless he is—
(a)a shot firer;
(b)a person doing so under the supervision of a shot firer; or
(c)a person appointed to fire shots by fuse.
(2) No person shall charge a shot hole, and no shot firer shall permit a shot hole to be charged, before it is necessary to do so for the purpose of firing a shot.
(3) No person shall begin to charge any shot hole unless he has satisfied himself by taking all reasonable precautions that it is so placed and drilled as to be safe for the firing of a shot.
(4) Except in the case of shots to be fired in one round or of a relieving shot fired in pursuance of the provisions of any scheme for the time being in force at the mine in pursuance of regulation forty-two for the purposes of a miss-fire, no person shall charge a shot hole (in the case of longwall working) within ninety feet of a charged shot hole or (in any other case) in the same face as a charged shot hole.
(5) No person shall charge a shot hole to be fired as one of a round in a cross measure drift, heading or ripping or in a shaft or staple-pit until all shot holes for that round have been completely drilled.