1076 LAWS OF MARYLAND. [CH. 437

2. When Cardox is fired all persons in the vicinity, in-
cluding the shot firer, shall be around a second corner or in
an equally safe place.

3. Blasting cables shall be as long as may be necessary
to assure the safety of the shot firer, attached only after
the charge has been placed in the borehole, and maintained
in good repair.

4. The charge shall be detonated with a permissible
shot-firing unit.

5. Cardox shall not be shot off the solid, over heavy
rock binders or shale, or in a "tight" shot.

6. Cardox misfires caused by the failure of the disk to
rupture shall not be approached until after the lapse of
15 minutes and shall be handled under the supervision of
a foreman or other competent designated person. Such
misfired shells shall be bled off before removal from the
hole, and shall be marked conspicuously upon removal
from the hole.

149C. Airdox. Where Airdox is used for blasting or
breaking down the coal, the following shall apply:

1. Compressed air shall be conducted from the com-
pressor to within a practical working distance of the face
by steel air lines tested to withstand an approximate pres-
sure of 20, 000 pounds per square inch.

2. Air lines shall be grounded at the compressor and, if
possible, at other low-resistance ground connections along
the lines, such as at bore-hole casings. They shall not be
connected in any way to tracks, water lines, or other elec-
tric power return conductors and shall be suitably insu-
lated where they cross electric wires or underneath the
track.

3. Unions shall be installed in steel air lines at not
more than 1000-foot intervals.

4. Shut-off valves shall be installed every 1, 000 feet in
all Airdox lines and, in all branch lines, at a point near
the main lines.

5. Airdox lines shall be protected at places where equip-
ment passes over, under, or adjacent to them; they shall
not be handled or repaired when air pressure is in the line.

6. Air lines shall be examined periodically for kinks or
other weaknesses and replaced immediately when defects
are found.