The U.S. Bureau of Mines constructed a facility in the multiple-entry section of its Bruceton Experimental Mine to evaluate the fire endurance of mine stoppings. The test stopping (up to 6 ft high by 18 ft wide) is subjected to a 70 min, 75,000 Btu/min liquid fuel tray fire. The stopping and adjacent areas are instrumented with thermocouples and heat flux gauges. Two 8 in. thick concrete block stoppings and a galvanized steel stopping were evaluated in four tests. A crack developed on the fire-exposed surface of both block stoppings where the flames were most intense. However, the unexposed surface of the stoppings was undamaged and its maximum temperature was about 80 degrees C. The steel stopping retained its structural integrity during the test. The temperature of the unexposed steel surface reached 490 degrees C, but combustible materials located 1 ft from the surface did not ignite. Heat energy transmitted across the steel stopping was approximately halved when a 3/4 in. thick coating of construction plaster was applied to its fire-exposed surface. All stoppings prevented the passage of flame and smoke.