The main objective of this project was to investigate the feasibility of fabricating thin-walled, explosion-proof enclosures for high-voltage electrical equipment for use in underground coal mines. The thin-wall construction technique is to prestress the enclosure with an internal methane-air explosion, then remachine the mating surfaces of the flame path to allowable tolerances. Test results indicate that the prestressed enclosures, which are considerably lighter in weight than conventional enclosures, can withstand significantly higher internal pressures without detrimental permanent deformation and subsequent venting of incendiary particles. In addition, the use of stainless steel foams as flame arresters in large explosion-proof enclosures was investigated. Test data indicate that the enclosure pressures can be easily limited to less than 10 psi, using "retimet" for the explosion pressure vent.