1394

LAWS OF MARYLAND

Ch. 418

(4) Tools for Opening Containers. Only
nonmetallic tools may be used to open containers
underground.

(1) (1) Manner of Exploding in General. In every mine,
permissible explosives or permissible blasting devices shall
be used for the blasting operation except as otherwise
expressly provided. The use of permissible explosives shall
comply with the following rules:

Rule 1 — Fired only with electric detonators of proper
strength.

Rule 2 — Fired with permissible blasting units unless
blasting is done from the surface.

Rule 3 — Boreholes in coal may not be drilled beyond
the back of the cut, nor into the solid rib, roof, or floor.
Shooting off the solid is prohibited.

Rule 4 — Boreholes shall be cleaned and checked to see
that they are placed properly and are of the correct depth,
in relation to the cut, before being charged.

Rule 5 — To prevent a blow-through, each portion of
the borehole where the height of the coal permits shall have
a burden in every direction of at least 18 inches before
being fired.

Rule 6 — Each borehole shall be stemmed with at least
24 inches of incombustible material, or at least one half of
the length of the hole shall be stemmed if the hole is less
than four feet in depth.

Rule 7 — In a gassy mine, an examination for gas shall
be made immediately before and after firing each shot where
onshift shooting is done.

(2)  Charges Between One and One-Half Pounds and
Three Pounds. Charges exceeding one and one-half pounds,
but not exceeding three pounds, shall be used only if the
borehole is six feet or more in depth; the explosive is
charged in a continuous train, with no cartridges
deliberately deformed or crushed, with all cartridges in
contact with each other, and with the end cartridges
touching the back of the hole and the stemming respectively;
and Class A or Class B permissible explosives are used. The
three pound limit does not apply to solid rock work such as
solid rock tunnels.

(3)  Firing Shots. A shot may be fired by any
certified shot firer in a mine using coal-cutting equipment.
The shot firer shall comply with the requirements of this
subtitle pertaining to blasting. In any mine where charging
or shooting is done on shift, each shot or group of
simultaneous shots shall be fired immediately after it is
charged.