Page 26 - Occupational Health & Safety, May 2019

PROTECTIVE APPAREL
eight-hour test. Initially there is no chemical permeation detected, then there is an increase in permeation rate, then a leveling off at the steady state permeation rate. The steady state permeation rate for this chemical stayed below the 1.0 ug/cm2-min thresh- old, so it would be reported that no permeation was detected after eight hours (480 minutes). But clearly the chemical did permeate through the material for most of the test. If you had access to this permeation curve, you would see this issue. But if you are only pro- vided a breakthrough time reported as >480 minutes, you might incorrectly assume that this material offered longer barrier than another material tested using the endpoint of 0.10 ug/cm2-min. It is important that CPC material permeation data be compared using ASTM F739 results with the 0.10 ug/cm2 -min criteria, as it is more stringent. Be sure to check what test method and what endpoint
was used for any CPC material permeation claims.
Full-Scale CPC Tests
In addition to chemical tests run on CPC materials previously described, testing also can be conducted to assess overall garment design or an ensemble of garment, gloves, respirator, etc. There are tests (ASTM or ISO methods) to check gas tightness, vapor inward leakage, and particle inward leakage of CPC. There also are many test methods to assess “liquid integrity” of CPC gar- ments and ensembles. A “passing” rating for full-scale tests does not mean that the garment/ensemble is 100 percent impervious to a specific hazardous chemical phase. For example, just because a garment holds out low surface tension water in a shower test does not mean that the garment will hold out liquid toluene under the same exposure scenario. You must still rely on permeation test data for specific chemical hazards. Even with this limitation, full gar- ment/ensemble tests are an excellent way to assess the robustness of a garment design and to evaluate PPE ensemble interfaces.
Summary
The more questions you ask when selecting CPC, the greater your ability to find the best match for your chemical hazards.
Susan Lovasic is Global Regulatory Affairs Manager—DuPont Per- sonal Protection.
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