Adequate protection?
April 1st 2007 Electrostatic discharges can be the cause of serious accidents in the work place; this hazard is made all the more treacherous because human beings are unable to detect the existence of static electricity.
While static dissipative Fire Retardant garments can provide workers with a certain level of protection, choosing the correct protective clothing is not always as clear-cut as it may seem, as Jim Findlay, Gore Workwear Associate, explains
Electrostatic charges are generated by low atmospheric humidity and are only registered by humans at around 3000V. However, if near flammable or explosive materials, particularly air-gas compounds, sparks resulting from electrostatic discharges can be deadly.
The majority of static dissipative rainwear jackets are also sold as Flame Retardant, certified as either EN 533 or EN 531 by material assembly. Both of these standards are complicated and difficult to unravel; this can potentially lead to great danger to workers who have been supplied with clothing by a buyer or specifier who is unfamiliar with the performance levels of the norm – while a garment may have been procured in good faith, it has been done so with a lack of understanding.
Tests conducted in the laboratories of W. L. Gore & Associates have shown that many static dissipative garments only meet the minimum requirements of certain EN norms, and the tests that they have to pass in the laboratory to gain accreditation bear little relation to the potentially hazardous conditions for which they are being purchased. FR norms are based on small propane flame laboratory tests, which in no way replicate the behaviour of small explosions, which could be caused by a static discharge.
Furthermore, the level of protection offered by a particular garment can be very confusing. For example, Index 1 of EN 533 means that you can offer FR polyester PPE garments against flame – provided the wearer has an FR coverall EN 533 Index 2 minimum underneath – even though the outer garment would melt and holes would form when exposed to heat and flame.
EN 531 A can be reached by material assembly tests – where the outer material can melt in the small propane laboratory test but the inner lining is resistant to the small flame.
GORE-TEX® static dissipative FR laminate has a face fabric of a modacrylic/cotton blend which complies with the most exacting demands (index 3) of standard EN 533 and fulfils the criteria of the European standard for industrial workers exposed to heat and flame (EN 531) and for the protection of welders (EN 470-1). This laminate is also non-melting and is available in EN 471 Fluo Yellow.
Gore-Tex static dissipative laminate is available as 2 or 3 layer in which the static dissipative Gore-Tex membrane made of PTFE (Polytetrafluoroethylene) is laminated to the modacrylic/cotton outer material. So that the static dissipative component is protected from damage, conductive carbon particles are distributed with the membrane. They are electrically connected and form a 10 000 times denser network than conventional conductive mesh structures.
Because the charge discharges constantly in all directions, there are no localised voltage spikes.
The static dissipative function does not detract from the tried and tested capacity of the GORE-TEX membrane to make a fabric 100% waterproof and at the same time highly breathable. The outstanding breathability of the GORE-TEX membrane is due to the fact that each pore of the membrane is 700 times larger than a molecule of perspiration. Unimpaired by its static dissipative function, the membrane inside the protective clothing continues to function as always: a drop of water is roughly 20 000 times larger than one of the pores of the Gore-Tex membrane – so water cannot penetrate from the outside.
Gore-Tex static dissipative garments were first adopted by gas companies in Germany and Austria, closely followed by Bord Gas in Ireland.
Choosing the correct static dissipative Flame Retardant garments could be critical to preventing injury to people or damage to plant and equipment. A gas vapour explosion in general disorientates those in the immediate proximity and produces heat and flame at a level well above the small propane gas flame used to test (and so pass) many flame retardant rain wear garments. All we can do is highlight that specifiers and buyers should be quite clear about the level of protection that they are purchasing. The question to ask is: Am I sure that I have the right product to protect people to the best level? If in doubt – ask! More articles from WL Gore & Associates Limited: | 
