Evaluation of anti-contamination garments in use at LLNL

Abstract

This paper describes tests conducted on LLNL anti-contamination and clean-room garments using flame exposures derived from federal and industry standards. Each garment was assigned to one of three groups (low, moderate, and high) based on its fire response and performance. Test results and analysis provide guidance in selecting protective clothing for operations involving high temperatures or potential ignition sources. INTRODUCTION On February 13, 1997, a fatal accident occuned at the Oak Ridge National Laboratory (ORNL) when a worker’s clothing caught fw during a torch-cutting operation. Following this incident, the Hazards Control Department at Lawrence Liverrnore National Laboratory (LLNL) conducted flammability tests of all anticontamination and clean-room garments used for operations. Of special concern was the performance of protective clothing used in areas where personnel are exposed to potential ignition sources from operations involving welding, cutting, pyrophoric metals, and other high-energy sources such as lasers. Tests were conducted to determine various parameters (ignition, flamespread rate, after-burn time, char length, amount of rnaterkd consumed, and afterglow time) for each garment. The results will provide guidance in the selection of protective clothing best suited for LLNL operations involving high temperatures or potential ignition sources. TESTING Twenty-two anti-contamination and cleanroom garments were collected from within LLNL. Each garment was assigned a number (1–22), then subdivided alphabetically into sets (e.g., 1A-E; 2A-E; etc.) in order to apply the equivalent flame exposures specified in the American Society for Testing and Materials (ASTM) D-1230 Standardl and the Federal Test Method (FTM) 191 Standard.z The flame exposure for the ASTM D-1230 Standard is reasonably reproducible, so the number of samples tested for each garment was limited to three. On the other hand, the flame exposure for the I?TM 191 Standard is more severe and generally burns faster, so five samples of each garment were tested and the results averaged to account for any variations in the flame-spread rate. ASTM D-1230 Standard To create the flame exposure specified in this standard, a small burner was fabricated using a 26-gauge needle. Butane was used as the fuel source, and the flame was adjusted to a length of 5/8 inch (1.59 cm) and controlled with precision valves and pressure gauges. Each sample was then inserted into a specimen holder at a 45° incline, with the flame positioned 3/4 inch (1.91 cm) from the lower end of the test sample. A thread was then placed across the sample (five inches up from the exposed area) to gauge the flame spread. The sample was exposed to the test flame for approximately one second (see Fig. 1). Automatic kick-4ack solenoid k~ Figure 1. Test apparatus. The sample holder was placed at a 45° angle for samples tested using the ASTM D-1230 flame exposure and at a 90° angle for samples tested using the FTM 191 flame exposure. Photographs and video records were taken of each test and used to calculate the flame-spread rate as well as other parameters for each sample. In some tests, the lower section of the sample being tested melted or burned but the flame did not extend up to the thread. In these cases, the total area burned or melted was measured and correlated with the length of burn time to derive an ornni-directional flame-spread rate (i.e., areakec). These results can be found in Table A1, Appendix A. FTM 191 Standard The flame exposure for this standard was created using a 3/8-inch (0.95 cm) diameter Bunsen burner, with the vents completely closed, and a special gas mixture as required by the standard. The flame was adjusted to extend approximately 1-1/2 inch (3.8 1 cm) above the burner. Each sample was then placed in a 3 x 12 inch (7.62 x 30.05 cm) specimen holder and held vertically 3/4 inch (1.9 1 cm) above the flame. Samples were exposed to the flame for 12 seconds. If ignition occurred, the sample was allowed to burn until either it was consumed or the f~e selfextinguished. The burn time was recorded after the flame was removed. If there was any afterglow, it was recorded from the time the flame went out until the glowing stopped. In cases where the afterglow time was lengthy, it was recorded as greater than a minute. A video record was made of each test and used to calculate the measurements for the various parameters. These results can be found in Table A-2, Appendix A. Char-length measurements were calculated for test samples that did not completely burn. Asrequired by the FTM 191 standard, a 4-ounce weight was attached to the sample corner exposed to the flame while the opposite corner was lifted. The material was allowed to tear (or pull apart) as the weight was lifted. These measurements can also be found in Table A-2, Appendix A.