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°C. The steel stopping retained its structural integrity during the test. The temperature of the unexposed steel surface reached 490°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.