Overviews

A Comparison Between Ignition Behaviours of 7 Different UK and World-Traded Coals in Air, and in a Mixture of Oxygen and Carbon Dioxide Gases Representative of Oxy-Combustion Conditions (PDF, 233 KB, 2009)
This paper describes the results of testing using a 20L ignition test chamber to test suspensions of 7 UK and world traded coals in air and O₂/CO₂ mixtures typical of oxy-combustion conditions.

Methods for Controlling Explosion Risk at Coal Mine Working Faces (PDF, 242 KB, 2007)
At coal mine working faces, simultaneous application of three basic elements reduces the methane explosion hazard: (1) adequate ventilation, (2) regular monitoring of gas concentrations, and (3) the elimination of ignition sources. This paper reviews the application of these elements in a manner relevant to Chinese coal mines.

Data & statistics

Frictional Ignitions in Underground Bituminous Coal Operations 1983-2005 (PDF, 888 KB, 2009-08)
NIOSH conducted a statistical study of available data regarding frictional ignitions in the United States from 1983 to 2005 to determine and define conditions controlling their occurrence.

History

A Centennial of Mine Explosion Prevention Research (PDF, 307 KB, 2010)
This paper provides a brief historical overview of full-scale mine explosion research conducted primarily at the USBM, now the National Institute for Occupational Safety and Health (NIOSH).

Guides

Recommendations for a New Rock Dusting Standard to Prevent Coal Dust Explosions in Intake Airways (PDF, 1397 KB, 2010-05)
This NIOSH report presents the results of extensive in-mine coal dust particle size surveys of dust samples collected from intake airways in 61 U.S. coal mines, representing all 10 MSHA bituminous Coal Mine Safety and Health Districts.

Models

Composition Change Model for Sealed Atmosphere in Coal Mines (PDF, 285 KB, 2010)
This paper presents a mathematical model based upon the conservation of mass principle that describes the flow of air (nitrogen and oxygen), methane and carbon dioxide into and out of a sealed atmosphere and the time-dependent changes in gas concentration within the sealed atmosphere.

Hazards

Factors Affecting Coal Particle Ignition Under Oxyfuel Combustion Atmospheres (PDF, 784 KB, 2011)
A set of 13 coals of different rank has been tested for ignition propensity in a 20-L explosion chamber simulating oxyfuel combustion gas conditions. Their char residues were also analysed thermogravimetrically. The effects of coal type, coal concentration (from 100 to 600 g/m3), O2 in CO2 atmospheres (up to 40% v/v) and particle size were investigated.

Gas Sorption and Transport in Coals: A Poroelastic Medium Approach (PDF, 803 KB, 2009-01)
In this paper, single-component gas sorption and transient diffusion processes are described within coal matrix exhibiting bimodal pore structure.

NIOSH Hazard ID 16 - Non-Conforming Rock Dust (PDF, 136 KB, 2011)
In September 2011 as part of an ongoing investigation, the National Institute for Occupational Safety and Health (NIOSH) determined that rock dust not conforming to the requirements in 30 CFR Part 75.2 for particle size and caking properties is being used in U.S. underground coal mines.

Measurement & analysis

Alternative Methodologies for Evaluating Explosion-resistant Mine Ventilation Seals (PDF, 6213 KB, 2003-10)
Discusses the evaluation of a seal evaluation method, based on a hydrostatic pressure loading concept, for in-situ testing of seals in an operating mine.

Analysis of Post-Explosion Residues for Estimating Flame Travel During Coal Dust Deflagrations (PDF, 1578 KB, 2011)
The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has conducted a series of large-scale explosion experiments at the Lake Lynn Experimental Mine (LLEM) to investigate the inerting effect of limestone rock dust. Numerous experiments were conducted using a pulverized Pittsburgh coal dust (PPC) mixed with limestone rock dust to achieve total incombustible contents varying from 67 to 82%. These dust mixtures were entrained and were subsequently ignited, if insufficient incombustible was present, by the ignition of a methane-air zone located at the closed end of the entry. Electronic flame sensors were positioned at regular intervals along the length of the entry to measure the flame travel. Post-explosion dust residue samples were taken along the entry after each explosion and analyzed to infer flame travel by measuring the thermal decomposition of limestone rock dust. Alcohol coking indices of the post-explosion residues were also measured. The alcohol coking test method is a forensic tool currently used by the Mine Safety and Health Administration (MSHA) in accident investigations.The determination of the extent of flame travel by these different measurement methods are discussed and compared. The rock dust solubility test described in this paper could assist accident investigators in more accurately establishing the flame limits of a dust explosion.

Analysis of Seismic Signatures from Gas and Dust Based Explosions at the Lake Lynn Experimental Mine (PDF, 959 KB, 2008)
A seismic monitoring system located at NIOSH's Lake Lynn Experimental Mine has monitored experimental gas and dust based explosions and impact tests. The results suggest a large explosion that's not restricted can generate potentially the same magnitude as a small explosion that is restricted.

The Brookwood Disaster and Electrical Requirements for Hazardous (Classified) Locations (PDF, 373 KB, 2007)
Researchers with NIOSH studied the electrical equipment ignition sources for the Brookwood and other disasters to develop recommendations for preventing similar disasters.

Characterization of Gas Flow in Longwall Gobs: Pittsburgh Coalbed, PA (PDF, 175 KB, 1999)
Investigation of the geologic and mining factors influencing the migration of longwall gob gas with a goal to optimize methane drainage strategies to reduce the volume of gob gas that reaches the underground workplace.

Coal Dust and Methane (PDF, 198 KB, 2008-06)
This article describes the Coal Dust Explosibility Meter (CDEM), a hand-held instrument developed by NIOSH, which uses optical reflectance to measure the explosibility of a rock dust and coal dust mixture, which is now commercially available.

Coal Dust Particle Size Survey of U.S. Mines (PDF, 211 KB, 2006-08)
NIOSH and MSHA conducted a joint survey to determine the range of coal particle sizes found in dust samples collected from intake airways of U.S. coal mines.

Determining Flame Travel Measurements from Experimental Coal Dust Explosions (PDF, 675 KB, 2010)
NIOSH conducted a series of large-scale explosion experiments at the Lake Lynn Experimental Mine (LLEM) to investigate the inerting effect of limestone rock dust. In this paper, the flame travel during a series of experimental coal dust explosions is measured using the conventional alcohol coking test and results from this test are compared to a newer method that involves measuring the rock dust solubility.

Determining the Source of Longwall Gob Gas: Lower Kittanning Coalbed, Cambria County, PA (PDF, 1166 KB, 1992)
Four coreholes were drilled (two before and two after mining) at a longwall mine in the Lower Kittanning coalbed to obtain coal and rock samples from overlying strata to determine their gas content at various times in the mining cycle. Test results indicate that 91 pct of the gas removed from the overlying strata came from coalbeds. Further analysis indicated that only 40 pct of the total gas produced from the panel actually came from the strata directly overlying the panel. The remaining volume of gas production probably migrated to the longwall gob from overlying, and perhaps underlying, strata immediately adjacent to the panel and perhaps from greater distances downdip because of the establishment of a long-term pressure gradient.

Detonation Wave Propagation in Underground Mine Entries (PDF, 116 KB, 2005)
This paper reports on a series of explosive detonation experiments conducted in NIOSH's Bruceton and Lake Lynn Experimental Mines to evaluate low-level (<6 psig) detonation wave propagation behavior in single- and multiple-entry configurations.

Effect of Coal Type and Oxyfuel Combustion Parameters on Pulverised Fuel Ignition (PDF, 112 KB, 2007)
This paper describes ignition tests on pulverised coal suspensions using a suite of coals of different rank and from different countries of origin and over a range of oxygen and coal concentrations of interest for oxyfuel combustion.

Evaluation of the Relative Importance of Coalbed Reservoir Parameters for Prediction of Methane Inflow Rates During Mining of Longwall Development Entries (PDF, 663 KB, 2008-09)
This study presents a reservoir modeling approach to investigate the relative effects of different coalbed parameters on the migration of methane into development entries. This work shows that coupling reservoir simulations with linear modeling yields a technique that can be applicable to different coalbeds.

Experimental Mine and Laboratory Dust Explosion Research at NIOSH (PDF, 2134 KB, 2000-05)
Explosion characteristics such as the minimum explosible concentration and the rock dust inerting requirements were measured for various combustible dusts. The explosion resistance characteristics of seals was also evaluated.

Explosion Effects on Mine Ventilation Stoppings (PDF, 9382 KB, 2008-11)
This joint MSHA and NIOSH study was designed to simulate actual explosion accidents in coal mines where some crosscut stoppings near the ignition location survived the initial explosion pressure pulse, but stoppings farther away were destroyed. The construction and testing methods, explosion test data, and postexplosion condition of each stopping design are presented in this report.

Explosion Evaluation of Mine Ventilation Stoppings (PDF, 233 KB, 2006-06)
NIOSH and the Mine Safety and Health Administration (MSHA) conducted joint research to evaluate explosion blast effects on mine ventilation stoppings at the NIOSH Lake Lynn Experimental Mine. The LLEM data showed that a total pressure of 52 kPa (7.6 psi) destroyed the solid-concrete-block stopping, ~36 kPa (~5.2 psi) destroyed the hollow-core concrete-block stopping, and 9 kPa (1.3 psi) destroyed the steel panel stopping.

Explosion Temperatures and Pressures of Metals and Other Elemental Dust Clouds (PDF, 1281 KB, 2007-07)
The Pittsburgh Research Laboratory of NIOSH conducted a study of the explosibility of various metals and other elemental dusts, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating explosion hazards in the minerals and metals processing industries.

Explosion Temperatures of Metals and Other Elemental Dust Clouds (PDF, 1476 KB, 2006)
NIOSH conducted a study of the explosibility of various metals and other elemental dusts dispersed in air, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating the explosion hazards in the minerals and metals processing industries.

From Scotia to Brookwood, Fatal US Underground Coal Mine Explosions Ignited in Intake Air Courses (PDF, 92 KB, 2009-01)
NIOSH researchers studied US underground coal mine explosions over a 30 year period to identify the ignition sources and ignition locations responsible for the most severe explosion events resulting in death. Recommendations are provided for electrical equipment design and installation to prevent future disasters.

The Limiting Oxygen Concentration and Flammability Limits of Gases and Gas Mixtures (PDF, 203 KB, 2009-06)
This paper presents data on the limiting (minimum) oxygen concentration (LOC), in the presence of added N₂, of methane (CH4, propane (C₃H₂₄), ethylene (C₂H₄), carbon monoxide (CO), and hydrogen (H₂), and some of their binary mixtures.

Methane-Air Detonation Experiments at NIOSH Lake Lynn Laboratory (PDF, 292 KB, 2010)
This paper describes the first phase of research aimed at understanding explosion pressures that can develop in coal mines and the factors that lead to high explosion pressure and possible transition to detonation.

The Modified Direct Method: A Solution for Obtaining Accurate Coal Desorption Measurements (PDF, 158 KB, 2001-05)
This paper covers the development of NIOSH's modified direct method to measure the gas content of coal samples.

News: Coal Mine Explosion Prevention (HTM, 17 KB, 2011)
Prevention of coal mine explosions requires a suite of control strategies, including sustaining a properly designed ventilation system, adequate sealing of abandoned areas, aggressive and frequent monitoring of methane, reduction of coal dust accumulations, and control of potential ignition sources through electrical safety and the use of permissible equipment. NIOSH continues to conduct research to address these areas to develop more effective intervention measures and provide the science to guide recommendations for implementation of these measures and related policy decisions.

Observations of Post-Explosion Dust Samples From an Experimental Mine (PDF, 55 KB, 2009)
In this study, there appears to be a very good agreement between observations of partially burnt coal particles under a SEM at low magnification and using floor dust samples have been collected and analyzed using the alcohol coking test and scanning electron microscopy (SEM) to estimate flame travel.

Overview of Dust Explosibility Characteristics (PDF, 583 KB, 2000-05)
Provides information on the explosibility and ignitability properties of dust clouds that can be used to improve safety in industries that generate, process, use, or transport combustible dusts.

Post-Explosion Observation of Experimental Mine and Laboratory Coal Dust Explosions (PDF, 760 KB, 2007-07)
The Pittsburgh Research Laboratory (PRL) of NIOSH and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. All these data will be useful in future forensic investigations of accidental dust explosions in coal mines, or elsewhere.

Post-Explosion Observations of Experimental Mine and Laboratory Coal Dust Explosions (PDF, 722 KB, 2006)
NIOSH and MSHA conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine and after laboratory explosions in the PRL 20-L chamber and the Fike 1 -m³ chamber. The dusts studied included both high and low volatile bituminous coals.

Rapid (Grab) Sampling During Full-scale Explosions - Microscopic and Analytical Evaluation (PDF, 3254 KB, 1988)
The Bureau of Mines has developed a system using a high-speed electropneumatic mechanism for the rapid (grab) sampling of dusts and gases during an explosion. The sampling system consists of an aluminum housing that incorporates two 30-cm3 preevacuated glass vials with rubber septums. Upon actuation, the sampling probe needle is driven through the septum with a pressurized air pulse, filling the tube with gas and dust from the mine explosion.

Rapid Sampling of Products During Coal Mine Explosions (PDF, 1576 KB, 1991-02)
This paper describes a U.S. Bureau of Mines investigation of large-scale coal dust explosions in an experimental mine using a high speed electropneumatic mechanism for the rapid grab-sampling of gases and dusts. This technique enables the monitoring of pyrolysis and charring in fuel dust particles, and the collection of gaseous combustion products, in both large and small-scale explosions.

Relationship Between Radiated Seismic Energy and Explosive Pressure for Controlled Methane and Coal Dust Explosions in an Underground Mine (PDF, 594 KB, 2012)
This paper describes the research conducted to quantify a relationship between measured values of radiated seismic energy and peak explosive pressure generated.

Results of In-Mine Research in Support of the Investigation of the Sago Mine Explosion (PDF, 15660 KB, 2009-09)
The information in this report was used by MSHA and WVOMHS&T as supporting data in their analyses and investigative reports of the Sago Mine explosion.

Technical Development of the Coal Dust Explosibility Meter (PDF, 128 KB, 2006)
The NIOSH Pittsburgh Research Laboratory, in collaboration with MSHA Technical Support, has devised a prototype handheld instrument that can provide a direct assessment of the potential explosibility of a coal and rock dust mixture. The Coal Dust Explosibility Meter (CDEM) is not intended to replace the current MSHA laboratory analysis of coal mine dust samples for incombustible content, but rather to serve as a supplemental device for enhancing mine safety through improved rock dusting practices.

Technology News 461 - Coal Dust Explosibility Meter (PDF, 142 KB, 1997-07)
Describes a device to enable mine operators and mine inspectors to make quick and accurate measurements of the explosive nature of coal and rock dust mixtures.

Technology News 465 - Method for Predicting Methane Emissions on Extended Longwall Faces (PDF, 30 KB, 1997-11)
A method is described for allowing operators to predict methane emissions from panels with increased face width.

Technology News 490 - An Inexpensive Device for Monitoring Explosions in Sealed Areas of Underground Mines (PDF, 288 KB, 2001-06)
Description of a passive, inexpensive technique for monitoring explosion overpressures within sealed areas in underground coal mines.

Use of Infrared Sensors for Monitoring Methane in Underground Mines (PDF, 393 KB, 2008)
This paper describes research conducted to compare the performance, including response time and accuracy, of selected instruments using infrared and catalytic sensors.

Case studies

Blasting Injuries in Surface Mining with Emphasis on Flyrock and Blast Area Security (PDF, 380 KB, 2004-01)
This paper describes several fatal injury case studies, analyzes causative factors, and emphasizes preventive measures.

The Borehole Monitoring Experiment: Field Measurements of Reservoir Conditions and Responses in Longwall Panel Overburden During Active Mining (PDF, 459 KB, 2008-06)
This paper describes the results of a NIOSH borehole monitoring experiment (BME) on an active longwall panel.

Reservoir Rock Properties of Coal Measure Strata of the Lower Monongahela Group, Greene County (Southwestern Pennsylvania), from Methane Control and Production Perspectives (PDF, 1922 KB, 2009-03)
This study presents reservoir and elastic properties of coal measure rocks in the Lower Monongahela Group in Greene County, southwestern Pennsylvania, of the Northern Appalachian Basin. The results presented in this study can be used as data sources for reservoir studies related to the production and control of methane.

Engineering controls

Design and Analysis of a New Method to Test Mine Seals (PDF, 1122 KB, 2009)
This report describes a new seal testing program that will provide essential validation data for mine seal analysis and design methods.

Evaluation of New Methods and Facilities to Test Explosion-Resistant Seals (PDF, 120 KB, 2001)
This paper provides a brief overview of the ongoing study to evaluate the use of these chambers for pressure loading of full-scale seal designs using compressed air, water, or internal gas explosions.

Explosion Pressure Design Criteria for Seals in U.S. Coal Mine - An Update on Work at NIOSH (PDF, 3824 KB, 2009)
This paper seeks to encourage scientific discussion among international peers since preventing explosions within sealed areas is of interest to underground coal operators and regulators.

Explosion Prevention in United States Coal Mines (PDF, 46 KB, 2007)
This paper outlines the legal standards and methods for protecting underground coal mines in the United States from explosions of methane gas and coal dust. New research will also be presented on the inertization of float coal dust in mines through the addition of inert stone dust and on the application of the Coal Dust Explosibility Meter, a handheld device developed by NIOSH to directly measure the explosibility of a coal dust - limestone dust mixture based on optical reflectivity.

How Does Limestone Rock Dust Prevent Coal Dust Explosions in Coal Mines? (PDF, 238 KB, 2009-09)
This study investigates how limestone rock dust prevents the propagation of coal dust explosions by assessing its changes in chemical composition.

A Hydrodynamics-Based Approach for Predicting the Blast Damage Zone in Drifting as Demonstrated Using Concrete Block Data (PDF, 919 KB, 2009-08)
This paper presents a blast design technique based on a hydrodynamic method and introduces modifications to account for different explosives from those used in a calibration test.

Mitigating Coal Dust Explosions in Modern Underground Coal Mines (PDF, 442 KB, 2009)
NIOSH has investigated several areas in which current practices may need to be updated in order to adequately protect mines against coal dust propagated explosions. Other closely related issues such as rock dust testing methods and sampling procedures are discussed.

New Rock Dusting Standard to Prevent Coal Mine Explosions (HTM, 13 KB, 2011)
While much progress has been made in preventing explosion disasters in coal mines, explosions still occur - sometimes producing multiple fatalities. Explosions and the resulting fires can kill or trap workers, block escape paths, and rapidly create deadly gases that threaten every worker underground. Underground mine explosions are caused by a buildup of flammable gas or combustible dust mixed with air in the presence of an ignition source. Rock dusting is a critical practice to prevent a coal mine explosion from occurring in the first place, making an explosion much less destructive if one does occur.

Passive Mine Blast Attenuators Constructed of Rock Rubble for Protecting Ventilation Seals (PDF, 736 KB, 2010-01)
This paper discusses some concepts and preliminary test results for a Passive Mine Blast Attenuator (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals.

Progress Toward Improved Engineering of Seals and Sealed Areas of Coal Mines (PDF, 1505 KB, 2009)
NIOSH has initiated a seals research program with collaborators from Safety in Mines Testing and Research Station (SIMTARS) in Australia, West Virginia University (WVU), the Naval Research Laboratory (NRL), and the U.S. Army Corps of Engineers (USACE).

Reducing the Fire and Explosion Hazards of Flame-Cutting and Welding in Underground Coal Mines (PDF, 368 KB, 2010-06)
This paper provides a summary of work done in a study on fires and explosions in underground U.S. coal mines that were caused by flame cutting and welding operations to determine the root causes of these types of fires and explosions.

Reducing the Fire Hazards of Flame-Cutting and Welding in Underground Coal Mines (PDF, 368 KB, 2010-06)
This paper provides a summary of the NIOSH conducted study on fires and explosions in underground U.S. coal mines caused by flame-cutting and welding operations to determine the root causes of these types of incidents.

Remote Gob Gas Venthole Monitoring and Cellular Telephone-Based Real-Time Data Transmission System (PDF, 844 KB, 2002-10)
Report on the development and field testing of a solar powered, remote gob gas venthole monitoring and cellular telephone-based real-time data transmission system.

Secondary Explosion Hazards During Blasting in Oil Shale and Sulfide Ore Mines (PDF, 2935 KB, 1995)
Laboratory and field testing results are presented for reducing dust and/or gas ignitions associated with blasting operations in oil shale and sulfide ore mining applications.

Technology News 473 - The Explosion Hazard From Hydrogen Gas Generation Inside Sealed Frames (PDF, 69 KB, 1998-06)
Discusses one type of explosion hazard that was discovered lurking inside sealed and filled plow frame sections when NIOSH investigated ignition incidents resulting from drilling into plow frames.

Technology News 489 - Reducing the Danger of Explosions in Sealed Areas (Gobs) in Mines (PDF, 536 KB, 2001-05)
Techniques are identified to reduce the probability of gob gas explosions.

Technology News 530 - Frictional Ignition of Methane-Air in the Presence of Liquid Hydrocarbons (PDF, 194 KB, 2008-03)
This briefly describes testing done to ignite methane-air in the presence of liquid hydrocarbons, and gives recommendations for limiting frictional ignition.

Videos

Technology News 535 - NIOSH Releases New Educational Video: Escape from Farmington No. 9: An Oral History (PDF, 197 KB, 2009-05)
Researchers with NIOSH have developed a training module to educate both new, inexperienced miners as well as veterans on important issues related to self-rescue and escape procedures.