Proton exchange membrane fuel cells (PEMFC) have been selected to replace conventional underground power sources such as diesel engines, to improve underground air quality, to reduce green house gas emissions and operating costs and to facilitate equipment automation. The effects of underground mining conditions, gases, dust and shock and vibration on the performance of PEMFC's were investigated during extensive testing in an operating underground metal mine. Neither the voltage-amperage nor the power-amperage curves showed significant damage effects, and a post-testing stack inspection showed minor pressure drop, at the higher current density and airflow rate. With the use of an air intake filter, little particle accumulation was registered in the stack, and effluent water testing revealed the presence of rock-derived particles, showing that the stack was able to purge itself of low particle concentrations. No physical damage was imposed to the stack, auxiliary system and hydrogen metal hydride storage unit. Fuel cell performance compared well to pre-test and initial construction power plant data generation. Further tests are recommended to study individual mine gas and particle mineralogy type effects. (C) 2004 Elsevier B.V. All rights reserved.