the cave says that the cave was intersected by a railway tunnel, and thus the cave accumulated soot that led to its closing to tourists. He says that "exploring of the cave is unpleasant because of the necessity of wading, crawling, climbing, and becoming covered with soot, which coats all the upward-facing surfaces." He says the soot extends well over a mile into the cave. 1980s-1990s Various academic expeditions: March 1982: Joel Sneed, Carole Sneed, and Larry O. Blair 2000s In 2005 the State of Tennessee's elevator inspectors required the Ruby Falls operators to seal the portion of the elevator shaft below Ruby Falls and the cave became totally inaccessible as of 2006. References . "Caves of Chattanooga" by Larry E. Matthews, 2007, Published by the National Speleological Society, , Chapter 1 - Lookout Mountain Cave, pages 13–30. Caves of Tennessee Landforms of Hamilton County, Tennessee Lookout Mountain