30 CFR 75.403 : Mineral Resources (§ 1.1 To Parts 1291-1299) — (§ 1.1 To Parts 105-199) — Mine Safety And Health Administration, Department Of Labor (§ 1.1 To Parts 105-199) — Coal Mine Safety And Health (§ 70.1 To § 90.301) — Mandatory Safety Standards - Underground Coal Mines (§ 75.1 To § 75.1916) — Combustible Materials And Rock Dusting (§ 75.400 To § 75.404) — Maintenance of incombustible content of rock dust.

Where rock dust is required to be applied, it shall be distributed upon the top, floor, and sides of all underground areas of a coal mine and maintained in such quantities that the incombustible content of the combined coal dust, rock dust, and other dust shall be not less than 80 percent. Where methane is present in any ventilating current, the percent of incombustible content of such combined dust shall be increased 0.4 percent for each 0.1 percent of methane.