Permeation of chemical warfare agents (CWAs) and relatively nontoxic simulants in several elastomer compounds is examined using a new design flooded surface, liquid permeation cell. Diffusivity (D) and permeability are determined for sulfur mustard and sarin CWA, and for the simulants: dichlorohexane, chloroethyl phenyl sulfide, diethyl methylphosphonate and diisopropyl methylphosphonate. Values of D calculated by several kinetic methods at different stages of the permeation process and from steady-state permeability are generally in agreement but lower than those obtained from immersion kinetics. Barrier effectiveness of the elastomer compounds towards the CWA and simulant liquids decreases in the order: butyl > EPDM much greater than nitrile silicone. Simulant and CWA permeation are correlated in terms of relative permeability and reduced breakthrough time. (C) 2004 Elsevier B.V. All rights reserved.