ANNEXE 4: FABRIC TESTING
PENETRATION VS PERMEATION Penetration is the physical process whereby a liquid or solid passes through a material via micropores , i.e. microscopic holes, in the fabric. It is especially relevant when referring to the particle penetration of a fabric or a whole suit. It is important to understand liquid penetration and repellency test data is generated during a 60 second test only. Consequently, it is only of value in the selection process to exclude those fabrics that allow chemicals to immediately penetrate. In order to assess whether a fabric protects the wearer against a speciﬁ c chemical for durations exceeding 60 seconds, the permeation data must be consulted.
Permeation is the process by which a chemical, in the form of a liquid, vapour or gas, moves through protective clothing material at a molecular level and this molecular creep can occur without any visible trace. This means it is possible for a liquid or vapour to permeate through a fabric even when there is no observed breaches or perforations in the fabric. The permeation process progresses in three steps: the substance is absorbed by the outside surface of the material; its molecules then diffuse through the material and ﬁ nally the molecules desorb at the other surface (inside). The standard test duration for permeation is up to 8 hours or until permeation has been detected.
Fabrics used in garments certiﬁ ed to Type 6 are typically only tested for liquid penetration and repellency. This is why the scope of type 6 garments is intended for applications with potential exposure to small quantities of ﬁ ne spray/mist or accidental low volume splashes and where wearers are able to take timely adequate action in case of contamination . Therefore, it is preferable to verify the permeation data of the fabric even for Type 6 garments.
Permeation and Penetration should not be confused. Many microporous fabrics which can offer good liquid repellency characteristics, i.e. low penetration properties, exhibit high permeation rates which means liquids, in practice, will quickly permeate through.
Test method Norm Scope/Principle
Penetration by liquids EN ISO 6530 Gutter test method determines indices of penetration, repellency and absorption by applying a fine stream of a test liquid to the surface of a clothing material resting in a inclined gutter.
Permeation by liquids EN ISO 6529 Method A
Permeation test method determines breakthrough detection time at normalized permeation rate and cumulative mass by analysing quantitatively the chemical concentration that has permeated after initial continuous contact with the chemical.
Surface resistance EN 1149-1
Antistatic test method is intended for materials used for electrostatic dissipative protective clothing to avoid incendiary discharge. A potential is applied to an electrode assembly rested on the fabric placed on an insulating base plate and the resistance of the fabric is recorded. The lower the resistance, the better the electrostatic dissipation.
Table 8. Type 6 certiﬁ ed garments tests.