5.1 This test method is used to measure chemical permeation through specimens of protective clothing under the condition of intermittent contact of a test chemical with the specimen. In many applications, protective clothing is contacted intermittently to chemicals, not continuously as is tested by Test Method F739.
5.2 This test method is normally used to evaluate flat specimens from finished items of protective clothing and of materials that are candidates for items of protective clothing.
5.2.1 Finished items of protective clothing include gloves, arm shields, aprons, suits, hats, boots, respirators, and the like.
5.2.2 The phrase specimens from finished items encompasses seamed or other discontinuous regions as well as the usual continuous regions of protective clothing items.
5.3 In some cases, it may be of interest to compare permeation behaviors that occur under conditions of intermittent contact with those that occur during continuous contact. Test Method F739 is recommended for measuring permeation under the conditions of continuous contact of the test chemical with the clothing specimen.
5.4 The breakthrough detection time, standardized breakthrough time, and the cumulative permeation are key measures of the effectiveness of a clothing material as a barrier to the test chemical. Such information is used in the comparison of clothing materials during the process of selecting clothing for protection from hazardous chemicals. Long breakthrough detection times and standardized breakthrough times and low cumulative permeation are characteristics of better barriers.
Note 1: At present, there is limited quantitative information exists about acceptable levels of dermal contact with most chemicals. Therefore, the data obtained using this test method cannot be used to infer safe exposure levels.
5.4.1 The reporting of a standardized breakthrough time greater than a specific time period does not mean that no chemical has permeated through the protective clothing material as the standard breakthrough time is determined based on the permeation rate reaching a level of 0.1 μg/cm2 min, indicating that some chemical has already permeated the specimen prior to the reported standardized breakthrough time.
5.4.2 Cumulative permeation represents the mass that permeates through a protective clothing material over a specific period of time for a specific surface area of material. It is possible to use this information to model how much chemical can enter an item of protective clothing for a particular exposure based on a knowledge of the exposed surface area, the free volume inside the protective clothing item, and amount of air mixing or air exchange for the protective clothing item.
5.5