MSHA issues emergency temporary standard on rock dusting

A Mine Safety and Health Administration emergency temporary standard (.pdf file) issued this week tightens requirements for rock dusting in underground mines.

Rock dusting involves applying pulverized limestone or another inert material throughout the mine to dilute the potential power of a coal dust explosion. The emergency temporary standard, which applies only to underground bituminous coal mines, requires mine operators to increase the total incombustible content of combined coal dust, rock dust and other dust to 80 percent from 65 percent in all accessible areas, and an additional 0.4 percent for each 0.1 percent of methane where methane is present in any ventilating current.

According to an agency press release, MSHA issued the emergency temporary standard based on its review of coal dust explosions and NIOSH recommendations (.pdf file) for a new rock dusting standard. The emergency temporary standard remains in effect until the agency promulgates a rule through the regular rulemaking process. Mine operators have until Oct. 7 to comply with the standard for newly mined areas and Nov. 22 for all other areas of the mine.

MSHA also issued a program information bulletin that provides guidance on the new standard.