Protective clothing - Electrostatic properties
BTTG™ has been at the forefront of electrostatic testing for the textile industry for over forty years. Our facilities were amongst the first anywhere in the world dedicated to examining the generation of static electricity in relation to textile materials. Static electricity testing has been part of the routine testing services offered by BTTG™ for some thirty-five years and we have been actively involved in the development of British, European and International test methods.
Discharges (sparks) from the human body and from clothing can ignite flammable gas, vapours, and dust clouds. The BS EN 1149 series of standards were developed to provide tests and requirements for fabrics and garments that would not ignite the most easily ignitable mixture of hydrogen, gas and air.
The test methods from the BS EN 1149 series of tests are as follows:
- BS EN 1149-1:2006 - Test method for measurement of surface resistivity.
- BS EN 1149-2:1997 - Test method for measurement of the electrical resistance through a material (vertical resistance).
- BS EN 1149-3:2004 - Test methods for measurement of charge decay.
BS EN 1149-1 & 3 state that if the fabric is washed in practise then the fabric has to be subjected to the cleansing procedure specified in BS EN 340:2003 Protective clothing, General Requirements to possibly remove any treatments that may enhance the fabrics anti-static properties.
The series of tests are also part of the essential requirements specified in the EU Directive 89/686/EEC, Personal Protective Equipment.
The test requirements for BS EN 1149-1 & 3 are specified in BS EN 1149-5:2008, Material performance and design requirements. The requirements specified are as follows:
BS EN 1149-1 - The maximum acceptable resistance specified is ≤2.5 ´ 109 W measured on at least one surface.
BS EN 1149-3 - The shielding factor should be greater than 0.2 and/or the half decay time be less than 4 seconds.
Additionally, for a material containing conductive threads in a stripe or grid pattern the spacing of the conductive threads in one direction shall not exceed 10mm.