The breakthrough time of sulfur mustard (SM) against blends of natural and nitrile rubbers was determined using the spot disc test (SDT) method. The breakthrough time of SM is closely related to the elongation properties of the blended rubbers. Blends containing higher proportions of nitrile rubber show better protective properties as revealed by higher breakthrough times. The diffusion of the oxygen analog of sulfur mustard (OA) across these blends follows an anomalous behavior in that, initially, they follow a Fickian behavior and later assume a non-Fickian mode.