(225 ILCS 705/24.05) (from Ch. 96 1/2, par. 2405)
    Sec. 24.05. Where rock dust is applied, it shall be distributed upon the top, floor and sides of all open places and maintained in such quantity that the incombustible content of the combined coal dust, rock dust and other dust will not be less than 65%. Where methane is present in any ventilating current, the 65% of incombustible content of such combined dust shall be increased 1% for each 0.1% of methane.
(Source: Laws 1953, p. 701.)