PURPOSE:  To reduce the occurrence of spontaneous combustion in underground coal mines, particularly in mines that have appreciable levels of methane, to reduce the fire hazards in coal mines associated with flame cutting and welding operations, and to evaluate the effectiveness of dry power chemical suppression systems in conveyor belt entries under high airflow conditions.

RESEARCH SUMMARY:  Most spontaneous combustion fires occur in worked-out areas that are not accessible and require remote detection and extinguishing efforts. This hazard is a particular concern in mines with both a high spontaneous combustion risk and high levels of methane, since most ventilation schemes utilized to remove methane from the mine exacerbate the spontaneous combustion hazards. An understanding of how various ventilation practices affect spontaneous combustion is needed. Research is required to develop ventilation methods that both remove the methane and minimize the risk of spontaneous heating. Case studies are being conducted to determine the causative factors and the role of ventilation in the heating events. The information from these studies, along with experiments to characterize gob ventilation, is being incorporated into computational fluid dynamic models to evaluate ventilation schemes to dilute methane and minimize the self-heating risk in spontaneous combustion-prone mines. In addition, models are being developed to evaluate various sealing and inert gas techniques to combat self-heating in gob areas. This research will result in improved ventilation practices and technologies to reduce the number of fires and the risk of spontaneous combustion fires in mines with both a high spontaneous combustion risk and high levels of methane.

Analyses of fires in the coal mining industry for the period 1990 - 2002 indicated that 110 of the 560 reported fires were the result of either flame cutting or welding operations. These fires resulted in 70 injuries and 2 fatalities. In a 2003 mine accident, a shaft explosion in West Virginia due to flame cutting caused 3 fatalities and 3 injuries. The root causes of flame cutting and welding fires are being determined and improved methodologies and technologies are being developed and evaluated to prevent these types of fires. Accident investigations are being scrutinized, workers interviewed, and flame cutting and welding operations at operating mines are being observed. Procedures, regulations, and other standards and existing guidelines are being analyzed to determine the root causes of cutting and welding fires in the coal sector and identify possible interventions. Training procedures and preventive equipment are being developed and evaluated. This research will result in new guidelines for flame cutting and welding in coal mining operations and a reduction in the number of fires and injuries due to flame cutting and welding operations.

A fire at a coal mine using belt entry air at the face was not extinguished by the dry powder chemical suppression system. This raised concerns about the air velocity limits of these systems in belt entries. NIOSH has partnered with MSHA to evaluate the effectiveness of dry powder chemical suppression systems in conveyor belt entries under high airflow conditions. Full-scale experiments are being conducted at the Lake Lynn Laboratory in the Fire Suppression Facility. The results will be used to provide guidelines for the installation and use of these systems in ventilated belt entries.