ANNEXE 4: FABRIC TESTING
CHEMICAL PERMEATION TEST The Chemical permeation of a material is tested according to the European standard EN ISO 6529. The resistance of a protective clothing fabric to permeation by a potentially hazardous substance is described by the determination of breakthrough time using the permeation rate as a cut-off.
Sorption of molecules of liquid onto the contracted (outside) surface.
Diffusion of the sorbed molecules across.
Desorption of the molecules from the opposite (inside) surface.
THE PERMEATION TEST CELL
The permeation test cell consists of two chambers that are separated by the fabric to be tested. The outside surface of the test fabric is exposed to the chamber containing the test medium (liquid or gaseous substance). Breakthrough of the substance is determined by measuring the concentration of the substance reaching the collection chamber per time unit.
This is the speed at which the test substance permeates through the test fabric. Permeation rate is expressed as mass of the test substance (μg) ﬂ owing through the fabric area (cm2) per time unit (min).
STEADY STATE PERMEATION RATE (SSPR)
The SSPR is the level where the permeation rate reaches a maximum and continues at that. This is the state when all forces affecting permeation have reached equilibrium.
MINIMUM DETECTABLE PERMEATION RATE (MDPR)
This is the minimum permeation rate that can be determined in the test. MDPR is a function of the sensitivity of the analytical measurement technique, the volume into which the permeated chemical is collected and the sampling time.
Minimum detectable permeation rates can be as low as 0.001 μg/cm2/min in certain cases.
Figure 3. Permeation.
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Flushing of chamber or discrete sampling
Reservoir for hazardous chemical
Figure 4. Permeation test cell.