(a) In all mines, dangerous accumulations of fine, dry coal and coal dust shall be removed from the mine, and all dry and dusty operating sections and haulageways and conveyors and back entries shall be rock dusted or dust allayed by other methods as may be approved by the director.

(b) All mines or locations in mines that are too wet or too high in incombustible content for a coal dust explosion to initiate or propagate are not required to be rock dusted during the time any of these conditions prevail. Coal dust and other dust in suspension in unusual quantities shall be allayed by sprinkling or other dust allaying devices.

(c) In all dry and dusty mines or sections thereof, rock dust shall be applied and maintained upon the roof, floor and sides of all operating sections, haulageways and parallel entries connected thereto by open crosscuts. Back entries shall be rock dusted. Rock dust shall be so applied to include the last open crosscut of rooms and entries, and to within forty feet of faces. Rock dust shall be maintained in a quantity that the incombustible content of the mine dust that could initiate or propagate an explosion shall not be less than eighty percent. The incombustible content of mine dust in return entries shall also be equal to or greater than eighty percent.

(d) Rock dust shall not contain more than five percent by volume of quartz or free silica particles and shall be pulverized so that one hundred percent will pass through a twenty mesh screen and seventy percent or more will pass through a two hundred mesh screen.

(e) If requested by the director, an operator shall provide records establishing the quantity of bulk and bag rock dust purchased for a period not to exceed the immediately preceding six months.