<p>Gassy underground mines commonly use explosion-proof (XP) enclosures to enclose electrical ignition sources to prevent the propagation of an internal methane-air explosion to a surrounding explosive atmosphere. Researchers at the National Institute for Occupational Safety and Health (NIOSH) conducted a lithium-ion battery thermal runaway test within a modified MSHA-approved XP enclosure to investigate thermal runaway containment. Thermal runaway produced jet flames emanating from the cover joint at several locations and distorted the cover joint and bottom plate of the enclosure beyond allowable limits per U.S. Code of Federal Regulations. The case study demonstrates that, under the specific conditions tested, XP enclosures may not provide adequate explosion protection against lithium-ion battery thermal runaway. This paper also explores some approaches to mitigate the hazard. Underground battery electric truck deployments and fires are reviewed. The findings and conclusions from this study are based on a limited sample set investigated under specific conditions.</p>