(1) Lay three samples of the belt, 60 ± 1⁄4 inches (152.4 ±0.6 cm) long by 9 ± 1⁄8 inches (22.9 ±0.3 cm) wide, flat at a temperature of 70 ±10 °Fahrenheit (21 ±5 °Centigrade) for at least 24 hours prior to the test;

(2) For each of three tests, place one belt sample with the load-carrying surface facing up on the rails of the rack so that the sample extends 1 ± 1⁄8 inch (2.5 ±0.3 cm) beyond the front of the rails and 1 ± 1⁄8 inch (2.5 ±0.3 cm) from the outer lengthwise edge of each rail;

(3) Fasten the sample to the rails of the rack with steel washers and cotter pins. The cotter pins shall extend at least 3⁄4 inch (1.9 cm) below the rails. Equivalent fasteners may be used. Make a series of 5 holes approximately 9⁄32 inch (0.7 cm) in diameter along both edges of the belt sample, starting at the first rail hole within 2 inches (5.1 cm) from the front edge of the sample. Make the next hole 5 ± 1⁄4 inches (12.7 ±0.6 cm) from the first, the third hole 5 ± 1⁄4 inches (12.7 ±0.6 cm) from the second, the fourth hole approximately midway along the length of the sample, and the fifth hole near the end of the sample. After placing a washer over each sample hole, insert a cotter pin through the hole and spread it apart to secure the sample to the rail;

(4) Center the rack and sample in the test chamber with the front end of the sample 6 ± 1⁄2 inches (15.2 ±1.27 cm) from the entrance;

(5) Measure the airflow with a 4-inch (10.2 cm) diameter vane anemometer, or an equivalent device, placed on the centerline of the belt sample 12 ± 1⁄2 inches (30.5 ±1.27 cm) from the chamber entrance. Adjust the airflow passing through the chamber to 200 ±20 ft/min (61 ±6 m/min);

(6) Before starting the test on each sample, the inner surface temperature of the chamber roof measured at points 6 ± 1⁄2, 30 ± 1⁄2, and 60 ± 1⁄2 inches (15.2 ±1.27, 76.2 ±1.27, and 152.4 ±1.27 cm) from the front entrance of the chamber must not exceed 95 °Fahrenheit (35 °Centigrade) at any of these points with the specified airflow passing through the chamber. The temperature of the air entering the chamber during the test on each sample must not be less than 50 °Fahrenheit (10 °Centigrade);

(7) Center the burner in front of the sample's leading edge with the plane, defined by the tips of the burner jets, 3⁄4 ± 1⁄8 inch (1.9 ±0.3 cm) from the front edge of the belt;

(8) With the burner lowered away from the sample, set the gas flow at 1.2 ±0.1 standard cubic feet per minute (SCFM) (34 ±2.8 liters per minute) and then ignite the gas burner. Maintain the gas flow to the burner throughout the 5 to 5.1 minute ignition period;

(9) After applying the burner flame to the front edge of the sample for a 5 to 5.1 minute ignition period, lower the burner away from the sample and extinguish the burner flame;

(10) After completion of each test, determine the undamaged portion across the entire width of the sample. Blistering without charring does not constitute damage.