30 CFR § 77.1911 Ventilation of slopes and shafts.
(a) All slopes and shafts shall be ventilated by mechanical
ventilation equipment during development. Such equipment shall be examined
before each shift and the quantity of air in the slope or shaft measured
daily by a certified person and the results of such examinations and tests
recorded in a book approved by the Secretary.
(b) Ventilation fans shall be:
(1) Installed on the surface;
(2) Installed in fireproof housing and connected to the
slope or shaft opening with fireproof air ducts;
(3) Designed to permit the reversal of the air current,
and located in an area which will prevent a recirculation of air from the
slope or shaft or air contamination from any other source;
(4) Equipped with an automatic signal device designed to
give an alarm in the event the fan slows or stops which can be seen or heard
by any person on duty in the vicinity of the fan, except where fans are
(5) Offset not less than 15 feet from the shaft; and
(6) Equipped with air ducts which are fire resistant and
maintained so as to prevent excessive leakage of air;
(b)(6)(i) Flexible ducts shall be constructed to permit
ventilation by either exhausting or blowing methods and when metal air ducts
are used, they shall be grounded effectively to remove static and other
(b)(6)(ii) Ducts shall extend as close to the bottom as
necessary to ventilate properly.
(c) A qualified person, designated by the operator, shall be assigned
to maintain each ventilating system.
(d) The fan shall be operated continuously when men are below the
surface. Any accidental stoppage or reduction in airflow shall be corrected
promptly; however, where repairs cannot be made immediately, development work
below the surface shall be stopped and all the men not needed to make
necessary repairs shall be removed to the surface.