57.11052—Refuge areas.
Refuge areas shall be—
(a)
Of fire-resistant construction, preferably in untimbered areas of the mine;
(b)
Large enough to accommodate readily the normal number of persons in the particular area of the mine;
(c)
Constructed so they can be made gastight; and
(d)
Provided with compressed air lines, waterlines, suitable handtools, and stopping materials.