Permeation tests were conducted to determine if an alternate 1-in. stainless steel cell was equivalent to the ASTM standard 2-in. glass cell. Permeation tests were conducted according to ASTM Test Method for Resistance of Protective Clothing Materials to Permeation by Liquids or Gases (F 739-85). Sheet stock neoprene (0.41 and 0.81 mm) and sheet stock nitrile (0.41 mm) were challenged with n-hexane (99%). Seven replicates of each chemical/material were tested for each cell.
Data sets of breakthrough time and permeation rate were compared using a proposed ASTM Cell Equivalency Method, Standard Practice for Determining Equivalency of Optional Chemical Permeation Test Cells to that of the ASTM Cell—Draft, 10 April 1985. This method first determines the equivalence of cells in terms of precision, via an F statistic. Equivalence in accuracy (bias relative to the ASTM cell), is then determined via a comparison of absolute percent difference and a calculated t statistic.
Analysis of ASTM and alternate cell data demonstrated standard deviations were dependent on mean breakthrough times and mean permeation rates. Therefore, the proposed ASTM procedure utilizing pooled standard deviations could not be used to determine cell equivalency. Further test results to characterize both cells are presented along with alternative statistical methods to evaluate data in cell validation tests.