30 CFR § 75.211
Roof testing and scaling.
(a) A visual examination of the roof, face and ribs shall be made
immediately before any work is started in an area and thereafter as
conditions warrant.
(b) Where the mining height permits and the visual examination does
not disclose a hazardous condition, sound and vibration roof tests, or other
equivalent tests, shall be made where supports are to be installed. When
sound and vibration tests are made, they shall be conducted--
(1) After the ATRS system is set against the roof and
before other support is installed; or
(2) Prior to manually installing a roof support. This test
shall begin under supported roof and progress no further than the location
where the next support is to be installed.
(c) When a hazardous roof, face, or rib condition is detected, the
condition shall be corrected before there is any other work or travel in the
affected area. If the affected area is left unattended, each entrance to the
area shall be posted with a readily visible warning, or a physical barrier
shall be installed to impede travel into the area.
(d) A bar for taking down loose material shall be available in the
working place or on all face equipment except haulage equipment. Bars
provided for taking down loose material shall be of a length and design that
will allow the removal of loose material from a position that will not
expose the person performing this work to injury from falling material.