W.L. Gore and Associates – Meeting the Challenge of Stored Energy
There is no question that firefighters are better protected than ever before thanks to the huge advances made in technical fabrics over the last twenty years.
Structural fire kit is designed to protect the wearer from extreme heat and flame. Whole garment ensembles are regularly tested on manikins equipped with sensors in flashover conditions to evaluate protection performance and resistance to serious burns. These tests are carried out in special test facilities and normally involve the ensembles being exposed to the flashover flames for eight seconds at temperatures in excess of 1000 degrees. Composite swatches of the fabrics used in the garment are also tested in laboratory conditions.
However it is a modern day paradox of firefighter protection that the gear which will protect in the extremes of a flashover, does not always protect from burn injuries that can occur in sub flashover conditions. That is the type of injury that can occur when energy stored within the layers of the protective clothing is suddenly transferred to the firefighter, resulting at times in burns, but with no sign of any damage to the PPE or outer fabric.
While it’s essential that PPE is designed to protect from the extreme conditions, firefighters do not face them every day. In normal fire-ground conditions it is possible that a firefighter can be exposed to radiant heat for relatively long periods of time, which causes a build up of energy inside the layers of their protective clothing. When clothing is then compressed against the skin, for example when a firefighter crouches or flexes an arm, that stored energy transfers through and can result in a burn.
Some of these burns have been associated with reflective trim or additional reinforcement material that is attached to the outer shell of the garment. Also, the use of additional equipment such as harnesses for breathing apparatus can be a factor.
The presence of moisture within structural kit, accumulated from water spray or sweat has also been associated with stored energy or “steam burn” phenomena.
Performance standards for PPE in the USA and in Europe set the benchmark for testing against the most extreme environments but do not currently address the issue of stored energy. Similarly, structural firefighting suits and fabrics are always tested in dry conditions. They are never tested wet, which doesn’t take account of the risks of burn injuries associated with stored energy.
There are so many variable factors that potentially impact stored energy burns it is no easy feat to develop a detailed understanding of the issue and most of the current knowledge is reliant on anecdotal evidence from firefighters.
In Europe, the standards committees are reviewing requirements for a new physiology annexe to EN469. In the USA the NFPA 1971 standard introduced a requirement for a thermal insulation test that measures stored energy.
What all of this underlines is that it is so far impossible to create one standard fire suit that will protect from all eventualities on a fire-ground. However progress since the cork helmets, woollen jackets and PVC leggings of 25 years ago has been dramatic.
An incredible level of protection from flashover has been created and that is unlikely to change much in the coming years, as the focus moves to physiology and comfort and dealing with the variables that contribute to the effects of stored energy. This is where the next major changes in firefighter PPE will occur. It will be driven by testing against a much broader range of conditions than just the extreme and will eventually include all of the components that impact PPE as one unit, rather than testing each in isolation.
For more information, go to www.gore-workwear.co.uk.