An emergency temporary standard was issued in September 2010, and the final rule maintains the same requirements as the ETS. The rule requires mine operators to maintain the percentage of incombustible content of the combined coal dust, rock dust and other dust at 80% in all accessible areas of underground bituminous coal mines, as well as an additional 0.4% for each 0.1% of methane where methane is present in any ventilating current. The final rule, like the ETS, increases the total incombustible content for all areas of the mine, other than return air courses, from 65% to 80%.