Microporous membranes were fabricated with Silastic-445 (from Dow Corning of Canada Limited) by using Luperco CST (L-CST) as catalyst and a perchlorate micropore producing additive (MPPA). Gas permeability, percent elongation, and tensile strength data show that membranes prepared with MPPA have high gas transmission rates, high percent elongation, and sufficient mechanical resistance. Scanning electron microscopic analyses reveal that the microporous silicone membranes prepared with a medium concentration of MPPA yield uniform pore distribution, the maximum pore size being <4 μm.