Page 23 - Occupational Health & Safety, December 2018

4. Changes to ASTM F1930 instrumented Thermal Manikin Test
The ASTM F1930 Thermal Manikin Test determines the per- cent body burn of an FR fabric. The methodology requires the use of a specific size and cut FR garment to be placed over 100% cotton t-shirt and briefs on an instrumented manikin with more than 100 sensors.
Standardizing this test helps ensure the ability to reproduce thermal exposure, with the only variable in the garment perfor- mance being the specific fabric tested.
NFPA 2112-2018 includes three changes to ASTM F190 Ther- mal Manikin Test, which improve standardization. Most notable, the approved garment design for the test is now a slightly larger, looser-fitting coverall that may lead to lower percent body burn. A larger garment also mimics what should be worn in the field, pro- viding insulating air gaps that better prevent heat transfer to skin. The updated standard also includes changes to better correlate test results between different test labs. NFPA 2112-2018 now requires all labs to test reference garments made from specified 4.5-ounce and 6.0-ounce aramid based fabric, resulting in specified predicted body burn percentage ranges at 3.0-second exposures for both fabric weights. Similarly, manikin systems must now be calibrat- ed over three heat flux exposures: 4,000 W/m2, 8,000 W/m2, and 12,000 W/m2. These new requirements for base test reference gar- ments and manikin calibrations enable the various testing labs to demonstrate reproducibility.
5. Changes to ASTM D6413 Vertical Flame Test
The ASTM D6413 Vertical Flame Test method determines the char length of FR fabrics. The char length is a basic start- ing indicator of performance, representing the extent to which a fabric might burn upon flame exposure. ASTM D6413 is the test method used for basic flame resistance. NFPA sets the test results’ performance criteria.
NFPA 2112-2018 now references the latest version of ASTM D6413 from 2015, which changed the way that tear weights are chosen to determine char length. The test method has remained the same: a 12-inch strip of FR fabric exposed for 12.0 seconds to a flame that must result in fewer than 4.0 inches in char length to pass NFPA 2112 requirements. The measurement method of the char length, however, has evolved. Now, after the flame exposure, the tear weight chosen to attach to the exposed fabric, which deter- mines the char length, could possibly change. The previous method was based on a fabric’s “basis weight,” or the fabric weight prior to applying any FR engineering or coating. The new method deter- mines tear weight based on the finished weight of the fabric. More- over, fabrics between 6.0 and 15.0 ounce per square yard, com- monly used in FR daily wear, will be tested using the 0.2-kilogram weight versus the 0.1 kilograms previously used.
Moving to a heavier tear weight could potentially affect some FR manufacturers, as it will cause fabrics that previously passed the test to now possibly fail, especially those with cotton-rich base materials. This should not be an issue for FR fabrics from reputable manufacturers, however, and can even perhaps further support their performance.
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