Inflatable stoppings are currently marketed for production use, and numerous mining companies have become interested in using such stoppings in rescue and recovery operations. The Bureau of Mines therefore evaluated the concept of using inflatable stoppings in emergency situations. The stoppings tested by the Bureau were 12- foot-diameter spheres inflated with a blower operated by a small battery pack. Experiments were conducted with the stoppings in a full-scale wooden mine model to evaluate their ability to withstand sliding or slippping at various internal and differential pressures, puncture resistance, various inflation techniques, and internal leakage from the stoppings. The stoppings were then installed and tested in the Bureau's safety research coal mine at Bruceton, Pennsylvania, To determine their effectiveness as mine air barriers. Despite some encouraging results obtained with the model and in-mine studies, the stoppings did not perform well in two operating metal mines where they proved difficult to erect and inadequate as air barriers.