Editor’s Note: FireRescue1 columnists Jeff and Grace Stull argue that the test method for determining turnout gear’s thermal protective preformance should not be altered because the new method somehow lowers a garments overall TPP score. In this piece, Globe’s Pat Freeman offers an alternative point of view as to why the new test method is the correct choice. The Stulls and Freeman are voting members on the NFPA comittee that decides this issue.
By Pat Freeman
As with most things in life, every argument has two sides. I have the pleasure of sitting on several NFPA technical committees with Jeff and Grace Stull and can tell you that it is normal, and actually very acceptable, that reasonable people can disagree reasonably.
The NFPA 1971 technical committee is made up of very passionate people from several different walks of life: firefighters, manufacturers, special experts, consumers, independent service providers, labor, researchers and even enforcers. It is important to note that all of these people care deeply about firefighter safety, regardless of how they vote.
The issue with the change to the TPP test method in NFPA 1971 is rather complicated. First, there is only very limited data at this point to support that all TPP values will be decreased with this change to the ASTM test method.
There is data, however, to support that the ASTM method offers less variability in test results than the current TPP test method. It is unfortunate that because we have seen some values decrease with preliminary testing, even though some values actually increased, the overriding fear is that we are making a change that could or might result in lower test values.
Second, as anyone who runs this test can verify, under the current test method it is not at all unusual to see a two, three or even more point shift in the results — up or down — when multiple samples of the same three-layer composite is tested. It is very important to note that while the TPP certification values reported by Underwriters Laboratories are accurate, they are not absolutes.
For example, TenCate Protective Fabrics, the world’s only producer of Advance outer shell fabric, reports a TPP value of 42.1 when Advance is tested with Caldura SL3 thermal liner and a Crosstech 2C moisture barrier. However, the UL data sharing test value on the exact same composite is report at 46.2 — for the exact same materials from the exact same suppliers.
One reason for this variability is that the test is run on multiple layers, and material weights can and do vary; the NFPA does not set weight requirements — only design and performance requirements. Any of the individual layers could be slightly higher or slightly lower in weight than the last composite tested, which definitely affects the overall composite weight and the final TPP value.
To illustrate this point, consider that it is quite acceptable for the 7.0-OSY (ounces per square yard) Advance shell fabric to actually weigh in at 7.3, for the 5.0-OSY Crosstech to weigh 5.4, and the 8.3-OST three-layer E89 to have a weight of 8.7.
With this heavier combination, the total ensemble weight would increase by almost a full ounce per square yard, greatly increasing the final TPP test result. And since fabrics are produced from fibers, this change in weight actually occurs within the individual rolls of fabric. While changing the test method will not address the inconsistency in fabric weights, it can make the final test results more consistent.
Thirdly, the fire service has been made aware that DuPont said it will no longer produce Nomex filament used in the production of any thermal lining material that offers a “slick” face cloth.
Given the combination of having to certify all existing and new composites to the 2012 revision of NFPA 1971 — which always results in new test values — coupled with a change in the Nomex filament facecloth thermal liners, it is an ideal time to start using the less variable test method to establish baselines for the new materials.
I support moving towards the ASTM test method for thermal protective performance because I truly believe it will provide more consistent test results overall. As pointed out, even without a change to the test method, we routinely see differences in TPP values in annual retesting using the current method.
In this case, the change means less variable test results going forward, with better reproducibility. As one other member of the committee who also voted in favor of the ASTM test method pointed out, adopting the ASTM method will not result in lowering the thermal protection for firefighters.
About the author
Pat Freeman has been involved with the fire service for more than 33 years and is a 20-plus-year member of the Technical Committee for NFPA 1971, Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting. She served as the Technical Committee Secretary for NFPA 1971 from 1995 until 2007, and remains an active member of the Technical Committees for both 1971 and its associate standard, 1851. She also serves as an alternate on the NFPA Technical Correlating Committee. She is the technical services manager for Globe Manufacturing.