Permeation Tychem LV is backed by extensive documentation and provides at least 30 minutes protection against more than 282 chemical challenges. These not only include live chemical warfare agents, but toxic industrial chemicals, which are more likely to be encountered during a terrorism incident according to experts. ® Physical Properties of DuPont™ Tychem® LV Property Permeation Data for ASTM Recommended List of Chemicals for Evaluating Protective Clothing Materials (ASTM F1001) Physical Phase Average Permeation Rate, µg/cm2/min Chemical Name Average Normalized Breakthrough Time, min >480..