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DuPont reports on the major threats to the modern firefighter and the next-generation technologies becoming available to combat them
When people think about the risks faced from major fires and the protection required for firefighters, their immediate thought is quite obviously the need to safeguard against the direct heat and flames generated by a blaze. Naturally, protection against these factors has to be the priority, otherwise firefighters will simply be unable to work in these supremely hostile environments. And indeed, the ongoing development of ever more advanced clothing continues to deliver increasingly improved protection against heat and flames.
But when one looks at the personal protective equipment (PPE) and particularly the clothing firefighters need to wear for structural firefighting, it needs to be recognised that while providing protection against the heat and flames of a fire, the equipment is also heavy and bulky and prevents the evacuation of body heat. Therefore, it becomes unsurprising to discover that actually the major threat to firefighters today is heat stress or over-exertion. Available statistics from the US back this up and show that roughly two-thirds of firefighter fatalities are related to heat stress; and the next highest threat is the danger created by toxic smoke particles. These two factors clearly need to be addressed in the development of cutting-edge technologies for deployment in next-generation firefighting apparel.
Taking the first of these, a major axis of development in the industry today is the reduction of heat stress. There are many different possibilities such as reducing the overall weight and bulkiness of the clothing, improving its sweat management or specially adapting the gear to the situation. The second high-level risk is toxic smoke particles – even a cursory analysis of smoke particles will reveal that most the substances found are considered to be highly carcinogenic. Long-term studies in the US and in Europe have shown that firefighters tend to have a higher cancer rate versus peer worker groups and the general population.
In addition to protective clothing, clearly firefighters will also wear respiratory protective devices to protects the respiratory tract and face against the penetration of toxic substances. However, numerous studies have shown that toxic organic substances are present on the skin and that the concentration of these is highest in the neck and jaw areas compared to other parts of the body, essentially penetrating the common hood typically used by firefighters. This has meant not only the adjustment of intervention procedures, but also impacts upon the development, maintenance and cleaning of the firefighting kit/PPE.
To meet the evolution of these risks, DuPont has developed new protection technologies for firefighters. The company’s Nomex® Nano and Nomex® Nano Flex materials are non-elastic and elastic versions, respectively, and provide increased heat and flame protection, despite offering a reduction in thickness versus previously used materials. In addition, they also have the advantage of reducing heat stress due to the material’s light weight and its high level of breathability. While protection against heat and flame protection is inherent to the company’s Nomex® technology, Nano and Nano Flex build further upon the properties of Nomex to offer a non-woven material comprising submicron continuous fibres (see Fig 1), which deliver a superior protective barrier against both heat and toxic particles.
Figure 1: Comparing the width of a human hair to the fibres of Nomex® Nano/Nano Flex
The Nomex® Nano technology enables a similar level of thermal protection performance (TPP) to other products, but very importantly, it also delivers an improved total heat loss (THL) compared to typical thermal liners with a similar TPP – thereby helping to reduce heat stress (see Fig 2).
Figure 2: Nomex® Nano technology features improved THL with similar TPP
A further key benefit of the Nomex® Nano/Nano Flex barrier is protection from soot, which is composed of organic semi-volatile elements that have resulted from incomplete combustion. These are largely considered to be carcinogenic, according to IARC (International Agency for Research on Cancer). It is therefore vital that PPE must also help reduce the permeation of toxic particles to the skin. As an example, the Fluorescent Aerosol Screen Test (FAST) test method has demonstrated that particles of sizes up to 10 microns in size can pass through a standard protective hood – and soot particles are often 1.0 micron or smaller (see Fig 3).
Figure 3: Result of the FAST method showing the concentration of particles around the neck, face and ears
In the example shown, soot particles are deposited significantly on the neck, the back of the cheeks and the ears of the wearer, which matches the parts not covered by the protective mask. However, for example, a triple-layered hood designed with Nomex® Nano Flex in the middle layer provides not only flame resistance but is also thinner and lighter than other flame-retardant materials. Use of technology in the design of a hood can reduce the deposition of particles larger than 0.2 micron and above by more than 95 per cent (see Fig 4) and without detracting from wearer comfort or the situational awareness of a firefighter.
Figure 4: Barrier efficiency in relation to the particle size with a normal hood compared to a hood made with Nomex® Nano Flex
Overall, the exceptional elasticity offered by the technology provides unparalleled comfort and added protection against dangerous particles. This design helps keep potentially carcinogenic particles and other harmful contaminants away from the skin of the face and neck of firefighters – areas that are highly absorbent and more permeable than other parts of the body (see Fig 5). Hoods made with this new technology also meet the EN13911:2017 standard.
Figure 5: Florescent Particle Deposition on Head Forms (Left – Control Hood; Right – Elastic Nomex® Nano)
In addition, the properties of Nomex® Nano can also be applied to other areas beyond the protective hoods. It offers a higher level of porousness compared to other fire-resistant materials and can enable a reduction of up to 40 per cent in the thickness of the inner thermal layer of a firefighting jacket. This results in superior moisture management, offering an absorption rate of more than 30 per cent compared to other traditional thermal layers and without increasing the drying time.
In summary, these new technologies are at the forefront of firefighting PPE development: helping to reduce heat stress; protecting against toxic particles; decreasing the weight and bulk of firefighting gear; and also increasing mobility without compromising on thermal protection.
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