When firing from 1 to 15 blast-holes with safety fuse ignited
individually using hand-held lighters, the fuses shall be of such lengths to
provide the minimum burning time specified in the following table for a
particular size round:
| Number of holes | Minimum burning |
| in a round | time, minutes |
| 1..................| 2 |
| 2 to 5.............| 2 2/3 |
| 6 to 10............| 3 1/3 |
| 11 to 15...........| 5 |
In no case shall any 40-second-per-foot safety fuse less than 36 inches long
or any 30-second-per-foot safety fuse less than 48 inches long be used.
(v) The burning rate of the safety fuse in use at any time shall be
measured, posted in conspicuous locations, and brought to the attention of
all men concerned with blasting.
(w) Electric detonators of different brands shall not be used in the
(x) Adequate priming shall be employed to guard against misfires,
increased toxic fumes, and poor performance.
(y) Except when being tested with a blasting galvanometer:
(y)(1) Electric detonators shall be kept shunted until they
are being connected to the blasting line or wired into a blasting round.
(y)(2) Wired rounds shall be kept shunted until they are
being connected to the blasting line.
(y)(3) Blasting lines shall be kept shunted until immediately
(z) Completely wired rounds shall be tested with a blasting
galvanometer before connections are made to the blasting line.
(aa) Permanent blasting lines shall be properly supported, insulated,
and kept in good repair.
(bb) At least a 5-foot airgap shall be provided between the blasting
circuit and the power circuit.
(cc) When instantaneous blasting is performed, the double-trunkline
or loop system shall be used in detonating-cord blasting.
(dd) When instantaneous blasting is performed, trunklines, in
multiple-row blasts, shall make one or more complete loops, with crossties
between loops at intervals of not over 200 feet.
(ee) All detonating cord knots shall be tight and all connections
shall be kept at right angles to the trunklines.
(ff) Power sources shall be suitable for the number of electrical
detonators to be fired and for the type of circuits used.
(gg) Electric circuits from the blasting switches to the blast area
shall not be grounded.
(hh) Safety switches and blasting switches shall be labeled, encased
in boxes, and arranged so that the covers of the boxes cannot be closed with
the switches in the through-circuit or firing position.
(ii) Blasting switches shall be locked in the open position, except
when closed to fire the blast. Lead wires shall not be connected to the
blasting switch until the shot is ready to be fired.
(jj) The key or other control to an electrical firing device shall be
entrusted only to the person designated to fire the round or rounds.
(kk) If branch circuits are used when blasts are fired from power
circuits, safety switches located at safe distances from the blast areas
shall be provided in addition to the main blasting switch.
(ll) Misfires shall be reported to the proper supervisor and shall be
disposed of safely before any other work is performed in that blasting
(mm) When safety fuse has been used, men shall not return to misfired
holes for at least 30 minutes.
(nn) When electric blasting caps have been used, men shall not return
to misfired holes for at least 15 minutes.
(oo) If explosives are suspected of burning in a hole, all persons in
the endangered area shall move to a safe location and no one should return to
the hole until the danger has passed, but in no case within 1 hour.
(pp) Blasted areas shall be examined for undetonated explosives after
each blast and undetonated explosives found shall be disposed of safely.
(qq) Blasted areas shall not be reentered by any person after firing
until such time as concentrations of smoke, dust, or fumes have been reduced
to safe limits.
(rr) In secondary blasting, if more than one shot is to be fired at
one time, blasting shall be done electrically or with detonating cord.
(ss) Unused explosives and detonators shall be moved to a safe
location as soon as charging operations are completed.
(tt) When electric detonators are used, charging shall be stopped
immediately when the presence of static electricity or stray currents is
detected; the condition shall be remedied before charging is resumed.
(uu) When electric detonators are used, charging shall be suspended
and men withdrawn to a safe location upon the approach of an electrical