[Federal Register Volume 74, Number 161 (Friday, August 21, 2009)]
[Pages 42317-42318]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-20205]



Centers for Disease Control and Prevention

[Docket Number NIOSH-174]

Recent Coal Dust Particle Size Surveys and the Implications for 
Mine Explosions

AGENCY: National Institute for Occupational Safety and Health (NIOSH) 
of the Centers for Disease Control and Prevention (CDC), Department of 
Health and Human Services (HHS).

ACTION: Notice of draft publication available for public comment.


SUMMARY: The National Institute for Occupational Safety and Health 
(NIOSH) of the Centers for Disease Control and Prevention (CDC) 
announces the following draft Publication available for public comment 
entitled ``Recent Coal Dust Particle Size Surveys and the Implications 
for Mine Explosions.'' The document and instructions for submitting 
comments can be found at http://www.cdc.gov/niosh/review/public/174/default.html.
    Public Comment Period: Comment period from August 31, 2009 to 
September 30, 2009.

ADDRESSES: Written comments may be submitted to the NIOSH Docket 
Office, Robert A. Taft Laboratories, 4676 Columbia Parkway, MS-C34, 
Cincinnati, Ohio 45226. All material submitted to the NIOSH should 
reference docket number NIOSH-174 and must be submitted by September 
30, 2009 to be considered by the Agency. All electronic comments should 
be formatted as Microsoft Word. In addition, comments may be sent via 
e-mail to [email protected] or by facsimile to (513) 533-8285. A 
complete electronic docket containing all comments submitted will be 
available on the NIOSH Web page at http://www.cdc.gov/niosh/docket, and 
comments will be available in writing by request. NIOSH includes all 
comments received without change in the electronic docket, including 
any personal information. All information received in response to this 
notice will be available for public examination and copying at the 
NIOSH Docket Office, Room 111, 4676 Columbia Parkway, Cincinnati, Ohio 
45226, telephone (513) 533-8611.
    Background: Spreading rock dust in bituminous coal mines is the 
primary means of reducing the explosion potential of coal dust that 
collects during the normal workings of an active coal mine. 
Accordingly, guidelines have been established by the Mine Safety and 
Health Administration (MSHA) about the relative proportion of rock dust 
that needs to be present in both intake and return airways. 
Specifically, current MSHA regulations require that intake airways 
contain at least 65% incombustible content and return airways contain 
at least 80%. The higher limit for return airways was set in large part 
because fine ``float'' coal dust (100% < 200 mesh or 75 [mu]m) tends to 
collect in these airways. MSHA inspectors routinely monitor rock dust 
inerting efforts by collecting dust samples and measuring the 
percentage of total incombustible content (TIC). These regulations were 
based on two important findings: a survey of coal dust particle size 
that was performed in the 1920s and large-scale explosion tests 
conducted in the U.S. Bureau of Mines' Bruceton Experimental Mine (BEM) 
using dust particles of that size range to determine the amount of 
inerting material required to prevent explosion propagation.
    Mining technology and practices have changed considerably since the 
1920s when the original coal dust particle survey was performed. Also, 
it has been shown conclusively that as the average size of coal dust 
particles decreases, the explosion hazard increases. Given these 
factors, the National Institute for Occupational Safety and Health 
(NIOSH) and MSHA conducted a joint survey to determine the range of 
coal particle sizes found in dust samples collected from intake and 
return airways of U.S. coal mines. Results from this survey show that 
the coal dust found in mines today is much finer than in mines of the 
1920s, presumably due to increased automation and a greater reliance on 
mining machinery.
    In light of this recent comprehensive dust survey, NIOSH conducted 
additional large-scale explosion tests at the Lake Lynn Experimental 
Mine (LLEM) to determine the degree of rock dusting necessary to abate 
explosions using Pittsburgh seam coal dust blended as 38% < 200 mesh 
and referred to as medium-sized dust. Explosion tests indicate that 
medium-sized coal dust required 76.4% TIC to prevent explosion 
propagation. Even the coarse coal dust (20% < 200 mesh or 75 [mu]m) 
representative of samples obtained from mines in the 1920s required 
approximately 68% TIC to be rendered inert, a level higher than the 
current regulation of 65% TIC. In return airways, the particle size 
survey revealed that the average dust particle size is roughly the same 
as float coal

[[Page 42318]]

dust as defined in the Coal Mine Health and Safety Act of 1969.
    Given the results of the recent coal dust particle size survey and 
large-scale explosion tests, NIOSH recommends a new standard of 80% TIC 
be required in the intake airways of bituminous coal mines. The survey 
results indicate that the current requirement of 80% TIC in return 
airways is still sufficient and appropriate. In addition, NIOSH agrees 
with and endorses an earlier recommendation that new rock dusting 
standards should be based on a worst-case scenario (using high volatile 
coals) with no relaxation for lower volatile coals.

Director for Mining and Construction, 626 Cochrans Mill Road, 
Pittsburgh, PA 15236, (412) 386-6544, E-mail [email protected].
    Reference: Web address for this publication: http://www.cdc.gov/niosh/review/public/174/pdfs/RD-inertingOutToExtReview.pdf.

    Dated: August 14, 2009.
Christine M. Branche,
Acting Director, National Institute for Occupational Safety and Health, 
Centers for Disease Control and Prevention.
[FR Doc. E9-20205 Filed 8-20-09; 8:45 am]