Mining Publication: Laser Ignition of Flammable Gas

Emerging laser technologies are quickly gaining acceptance in the workplace. Besides the risk of human exposure, one safety concern with the more intense lasers is the potential for ignition of flammable gases, vapors, dusts, fibers, or flyings often found in hazardous (classified) industrial settings. In underground coal mines, lasers are being considered for remote measurement of explosive methane gas. Current federal safety regulations for underground mines contain no specific guidance for evaluating the safety of optoelectronic components such as diode lasers. The National Institute for Occupational Safety and Health is conducting research to help provide a scientific basis for developing appropriate safety guidelines for optical equipment in the presence of flammable methane gas and/or coal dust. One phase of the study is an experimental evaluation of methane-air ignition by laser heated small particles. Minimum observed igniting powers for laser energy delivered by 200-, 400-, and 800-micro m core diameter fiber optic cables and directed onto selected targets in methane-air atmospheres were 0.6, 1.1, and 2.2 W, respectively. Comparisons are made with other ignition phenomena including heated wires.