breakthrough shall be made on one side or the other of each room,
except the room adjoining said block, not to exceed forty feet from
the outside corner of the breakthrough to the nearest corner of the
entrance to the room, and on the opposite side of the same room a
breakthrough shall be made, not to exceed eighty feet from the
outside corner of the breakthrough to the nearest corner of the
entrance to the room, and thereafter breakthroughs shall be made not
to exceed eighty feet apart on each side of the room. No working
place, except those provided for within a distance of four hundred
feet of the principal openings of a mine, shall be driven more than
eighty feet in advance of a breakthrough or air-way. The required
air current shall be conducted to the breakthrough nearest the face
of such entry or room. All breakthroughs between entries, and when
necessary between rooms, except the one nearest the working face,
shall be closed and made air-tight by brattice, trap doors or other
means, so that the current of air in circulation may sweep to the
interior of the mine. Brattices between permanent inlet and outlet
airways shall be constructed in a substantial manner of brick,
masonry, concrete, or non-perishable material. In mines generating
fire-damp, so as to be detected by a safety lamp, the air current
shall be conducted by brattice, or other means, near enough to the
working face to expel the fire-damp, and prevent the accumulation of
the same. (Penalty, Sec. 976.)


Sec. 927. [=Safe appliances for hoisting persons.=] The owner,
lessee or agent of a mine shall provide and maintain safe
appliances, approved by the district inspector of mines, for the
ingress and egress of persons in each shaft, designated by such
owner, lessee or agent as a means of ingress and egress for persons