with a needle valve. It shall have a variable orifice to adjust the height of the flame. The barrel of the burner shall be at an angle of 25 degrees from the vertical. The burner may be equipped with an adjustable stop collar so that it may be positioned quickly under the test specimen. The burner shall be connected to the gas source by rubber or other flexible tubing.

(4) Gas supply system. There shall be a pressure regulator to furnish gas to the burner under a pressure of 103–259 mm. Hg. (2-5 lbs. per sq. in.) at the burner inlet. (Caution. Precautionary laboratory practices must be followed to prevent the leakage of methane. Methane is a flammable gas which can be explosive when mixed with air and exposed to a source of ignition, and can cause asphyxiation because of the lack of air.)

(5) Gas. The gas shall be at least 97 percent pure methane.

(6) Hooks and weights. Metal hooks and weights shall be used to produce a series of loads for char length determinations. Suitable metal hooks consist of No. 19 gauge steel wire, or equivalent, made from 7.6 cm. (3 in.) lengths of the wire, bent 1.3 cm. (0.5 in.) from one end to a 45-degree angle hook. The longer end of the wire is fastened around the neck of the weight to be used and the other in the lower end of each burned specimen to one side of the burned area. The requisite loads are given in table 1.

1 Weight of the original fabric, containing no seams or trim, is calculated from the weight of a specimen which has been conditioned for at least 8 hr at 21±1.1 °C (70±2 °F) and 65+2 pct relative humidity. Shorter conditioning times may be used if the change in weight of a specimen in successive weighings made at intervals of not less than 2 hr does not exceed 0.2 pct of the weight of the specimen.

(7) Stopwatch. A stopwatch or similar timing device shall be used to measure time to 0.1 second.

(8) Scale. A linear scale graduated in mm. or 0.1-inch divisions shall be used to measure char length.

(9) Circulating air oven. A forced circulation drying oven capable of maintaining the specimen at 105+2.8 °C. (221±5 °F.), shall be used to dry the specimen while mounted in the specimen holders. 3

(10) Desiccator. An air-tight and moisture-tight desiccating chamber shall be used for cooling mounted specimens after drying. Anhydrous silica gel with an indicator shall be used as the desiccant in the desiccating chamber. Replace or reactivate the desiccant when it becomes inactive.

(11) Hood. A hood or other suitable enclosure shall be used to provide a draft-protected environment surrounding the test chamber without restricting the availability of air. This enclosure shall have a fan or other suitable means for exhausting smoke and/or toxic gases produced by testing. (12) Extinguishing plates. Extinguishing plates shall be used to extinguish afterglow. The plates shall be metal, approximately 35.6 cm. x 5.1 cm. (14 × 2 in.) which fit within the opening of the specimen holder. The bottom plate shall be the thickness of the specimen holder and the top plate shall be at least 0.32 cm. (% in.) thick. A suitable metal specimen mounting block may be used for the bottom plate.

(b) Mounting and conditioning of specimens. (1) The specimens shall be placed in specimen holders so that the bottom edge of each specimen is even with the bottom of the specimen holder. Mount the specimen in as close to a flat configuration as possible. The sides of the specimen holder shall cover 1.9 cm. (34 in.) of the specimen width along each long edge of the specimen, and thus shall expose 5.1 cm. (2 in.) of the specimen width. The sides of the specimen holder shall be clamped with a sufficient number of clamps or shall be taped to prevent the specimen from being displaced during handling and testing. The specimens may be taped in the holders if the clamps fail to hold

3 Procedure 1(1.1.1) of ASTM D 2654-71 "Standard Methods of Test for moisture content and moisture regain of textile material," describes a satisfactory oven (1972 Book of ASTM Standards, part 24, published by the American Society for Testing and Materials, 1916 Race Street, Philadelphia, Pa. 19103).