293.400. 1. The operator of a coal mine shall not permitexcessive accumulation of coal dust in any part of the mine.Where mining operations raise an excessive amount of dust, wateror water with a wetting agent added to it or other effectivemethods shall be used to allay such dust at its source.
2. All coal mines, except those mines or those locations ina mine in which dust is too wet or too high in incombustiblecontent to propagate an explosion, shall be rock-dusted to withinforty feet of all active working faces and all open crosscutswithin the forty-foot zone shall be rock-dusted. If the dust ina mine or any part of it is wet but becomes dry, the mine or anyportion of the mine so affected shall be rock-dusted as soon asit becomes dry.
3. Where rock dust is applied it shall be distributed uponthe top, floor and sides of all open places and maintained insuch quantity that the incombustible content of the mine dustwill not be less than sixty-five percent.
(L. 1959 S.B. 188 ยง 45)