Last week, MSHA issued an emergency rule to require mine operators to use enough rock dust to make the incombustible content in clean-air intake tunnels also measure 80 percent of all dust measured.
In doing so, MSHA chief Joe Main cited a May 2010 report in which NIOSH recommended that change. Main didn't mention that NIOSH also had made similar recommendations in separate reports issued in 2006 and 2009.
In that May 2010 report, NIOSH researchers noted that questions about the adequacy of the 65 percent incombustible-content requirement were raised as far back as the 1929 Bureau of Mines report on which the requirement originally was based.
Mine safety experts and researchers who study mine explosions have been arguing for many years that the very tiny coal-dust particles created by advanced mining techniques -- especially those using longwall machines -- require more rock dust and called for a tougher rock-dusting standard.
Michael Sapko, a now-retired NIOSH researcher, outlined similar questions about the rock-dusting standards in a 1989 report.
"There is little data regarding the rate of float dust deposition in mechanized mines, but there is no doubt that it correlates with production rates," Sapko said. "With the increased utilization of longwall mining methods it represents a problem of growing concern."
Regardless of the standard, the problem of taking rock-dusting samples and getting timely results remains. Dust samples from around the country are analyzed at one MSHA lab in Mount Hope, and the work can take two weeks or more.
At Upper Big Branch, for example, MSHA inspectors took rock-dusting samples during a visit to the mine on March 13 of this year, but at least in part because of the time involved in analysis, MSHA did not get around to citing the mine for inadequate rock-dusting until April 13 -- after the deadly explosion.
"Why in the world are we sending samples away for weeks' time in this day and age?" said longtime mine safety chief Davitt McAteer, who headed MSHA during the Clinton administration. "It hampers enforcement and it hampers the prevention cycle."
In a 2006 report, Sapko and fellow NIOSH researcher Harry Verakis outlined how the agency's "Coal Dust Explosibility Meter," or CDEM, could speed such enforcement actions.
"The CDEM's in situ explosibility measurement can help mine operators reduce the danger of operating under hazardous conditions of explosible dusts and help provide a better balance between the applied rock dust and generated coal dust," Sapko and Veraki wrote.
"Relative to compliance, an inspector could focus specifically on deficient or borderline samples for subsequent laboratory analysis," they wrote. "Most importantly, the CDEM shows promise as a useful tool for mine operators and safety inspectors for the in situ determination of the explosible nature of coal and rock dust deposits and thereby would enable immediate corrective action."
Coming Monday: Could buckets of water hung from mine roofs prevent coal-dust disasters?
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.