With limited space and few entries and exit points, working in confined spaces is serious business. These tunnels, silos, vats, access shafts, cargo containers, and storage bins often include inward-curving walls or downward-sloping floors, which have the potential to trap or asphyxiate. Other dangers encountered in confined spaces are unguarded machinery, exposed live wires, extreme temperatures, and inadequate ventilation, which increases air hazard risks. Many federal, state, regional, and provincial government agencies and industrial employers require workers to pass rope access confined space training courses prior to going on site.