State-of-the-Art Review of Permeation Testing and the Interpretation of Its Results

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Permeation testing is the most common means for assessing the effectiveness of clothing materials as barriers to chemicals, and standard procedures exist for conducting such tests. In recent years significant amounts of data have been generated. Unfortunately, much of the data has not been reported in sufficient detail to allow rigorous comparison, extrapolation, or generalization of the results. The purpose of this study is to summarize insights into the correct performance of the test and to present guidance that enables the comparison and interpretation of its results. Fick's laws are used to demonstrate the effects of analytical sensitivity; clothing material thickness and surface area; collection medium volume and flow rate; and test mode (i.e., open- versus closed-loop) on test results, particularly the measurement of breakthrough time. Strong evidence is presented that considerably more details of the experimental procedures are required if tests results are to be meaningful. At a minimum, the breakthrough time values must be reported with an indication whether the test was performed in open-loop or closed-loop mode and with characteristic values of the experiment—the analytical sensitivity of the instrument used to detect permeant, the surface area of the clothing material tested, and the collection medium flow rate (open-loop mode) or volume (closed-loop mode), as appropriate. In addition, the clothing material thickness and temperature must be reported. Even with such information, however, one cannot extrapolate or calculate what might be the breakthrough time at another set of test conditions. Additional information is required. Furthermore, the Fick's law analysis demonstrates that there is no apparent relationship between the times of breakthrough detection measured by open- and closed-loop methods. The advantages of closed-loop testing over open-loop testing are highlighted. Precautions are given when using the breakthrough time and the time lag as reported parameters.