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.
"Mining Laws of Ohio, 1921"
Anonymous
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.
"Mining Laws of Ohio, 1921"
Anonymous