30 CFR §57.22106
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Dust containing volatile matter shall not be allowed to accumulate on the surfaces of enclosures, facilities, or equipment used in surface milling in amounts that, if suspended in air, would become an explosive mixture. An explosive mixture of dust containing volatile matter is 0.02 ounce or more per cubic foot of air.