By Jeffrey O. and Grace G. Stull
Firefighters look to the independent NFPA certification of gear to assure themselves their PPE meets minimum requirements and will provide levels of safety consistent with their expectations. The governing standard, NFPA 1971, is comprehensive and incredibly detailed, establishing extensive criteria in several aspects of protective clothing and equipment performance. It is undoubtedly one of the more rigorous voluntary standards for protective clothing in the world.
Performance tests are aimed at several relevant properties and designed to demonstrate protection within acceptable levels. These tests may be applied to the complete item or materials, components, or assemblies of the item. For example, a number of the requirements applied to helmets are conducted with complete helmets as it is the "system" that has to work together to provide protection (such as the impact from a falling object).
Similarly, several footwear and glove tests are performed on whole items. However, for garments (coats and pants), there are only a couple of requirements that assess the full item. Currently, these tests include the overall liquid integrity test, the Drag Rescue Device (DRD) function test, and the Man-In-Simulant Test (MIST) for the CBRN option.
For garments, testing tends to focus on materials, components and assemblies because this approach makes the testing more manageable and accommodates manufacturers offering a greater diversity of options and features.
Tests on flat materials or components are simpler to perform and can be more easily interpreted. For example, it is a lot easier to measure the strength of a material by pulling a cut rectangular fabric specimen in a testing machine until it breaks, than it is to test the same piece of material while sewn into a protective coat.
Test samples can be routinely prepared from rolls of material instead of being taken from finished items. This approach to testing also permits more consistent results and allows manufacturers to evaluate a variety of different materials, material systems, and garment features.
The firefighting protective clothing industry uses many different outer shell, moisture barrier, and thermal barrier materials that collectively can yield hundreds of different combinations. A material and component testing methodology permits garment manufacturers to choose their offerings based upon having the material and component suppliers provide relevant test data for certification purposes.
In contrast, overall product or systems testing is harder to perform and more expensive. Garments are relatively complicated products to test for a number of reasons. The items include many different material layers and potential options and features such as pockets, trims, closure systems, and numerous other options. This complexity of the design creates variables in testing that could lead to less precise results (more scatter in the test data). When testing is performed with the garments placed on a person or manikin, testing becomes more variable because of fit issues and how different individual movement may affect test results. Finally, tests that consume full garments are also much more expensive than individual material or component tests.
Nevertheless, there are some types of performance properties that simply cannot be assessed without full product testing. For many years, criteria existed in NFPA 1971 that dictated to the manufacturer that the garment had to be designed to afford complete thermal and liquid protection.
Overall instrumented thermal manikin test
The Technical Committee responsible for NFPA 1971 has considered the implementation of an overall instrumented thermal manikin test.
Such test procedures have been standardized for evaluating protective garments used in petrochemical facilities during flash fire situations.
The test involves exposing clothing on a manikin outfitted with multiple sensors distributed over the manikin's body that register the amount of heat transfer from a simulated flash fire lasting from 3 to 12 seconds.
Computer interpretation of the sensor response predicts the body areas where second and third degree burn injuries would be sustained during the exposure.
While the test might appear to offer a good tool for evaluating full firefighter protective garment thermal protection, some studies have demonstrated that even long exposures (10-12 seconds) show very few differences between turnout clothing systems.
It was relatively straightforward to consider continuous thermal protection full layering materials on the individual firefighter. Gaps in these areas create a potential weak area for the clothing that in turn makes the firefighter more vulnerable. Compliance with this criterion (continuous thermal protection) could be demonstrated by a thorough examination of the clothing (see side bar). However, liquid protection was more difficult to determine through an inspection of the clothing design.
The overall liquid integrity test was introduced in NFPA 1971 during the 1997 revision to address overall garment liquid protection and overcome the shortcomings of a design requirement. The test, often referred to as the "shower" test, involves subjecting sample protective clothing items to a liquid spray exposure to assess the overall liquid protection provided by the garments. This test involves the following procedures and interpretation:
- The test is conducted with sample clothing, placed on a manikin that is dressed with a liquid absorptive undergarment.
- The clothed manikin is then sprayed with water treated with surfactant at a specific concentration and for a specified duration (the surfactant is added to simulate the "better" wetting characteristics of chemicals and blood or body fluids). For turnout clothing, the test lasts 20 minutes with the dressed manikin rotated through four different orientations with respect to the five nozzles that are positioned to the sides and above the dressed manikin.
- The liquid absorptive garment is then inspected to determine if any liquid penetrated the undergarment.
- Garments that show no evidence of liquid penetration pass the test.
Like many other NFPA tests, this requirement is not intended to simulate actual firefighter exposures. Instead, the test is designed with relatively long liquid spray exposures so that liquid penetration into the garment is readily detected by the test operator.
This test is important for demonstrating overall garment integrity because penetration tests on individual materials and seams cannot show how well the garment is designed and constructed to prevent liquid penetration. Therefore, the test is useful in specifically assessing garment closure systems, seam quality and overall design integrity.
The test has had a significant impact on garment design. Many manufacturers found it necessary to redesign their closures on the front and collar areas of coats to meet the requirement. Multiple launderings of the garment prior to testing also increase the severity of the test as laundering can remove the repellent finished from some materials and allow more liquid absorption in outer layers.
As applied to structural fire fighting clothing, the shower test only evaluates coats and pants. Interface areas such as the sleeve to glove, pant leg to footwear, and collar to hood and SCBA facepiece are blocked off and not evaluated. Nevertheless, the relatively new CBRN option evaluates the full ensemble including these interfaces and provides a more rigorous test of the entire ensemble for liquid-tight integrity.
Garments and ensembles offering liquid integrity keep firefighters safe from exposure to a variety of hazardous liquids including hot water, blood, body fluids, fireground chemicals, and other substances. This does not mean that structural fire fighting garments protect from all hazardous substances. Under many circumstances including the orientation of the firefighter and the type of liquid exposure, clothing can be overwhelmed and liquid will penetrate. Moreover, garments will not effectively stop vapors produced by liquids from penetrating or permeating through the materials. Still, garments with adequate integrity significantly limit exposure and provide overall greater protection.