The manufacture of polycrystalline silicon generates a vent gas comprised primarily of hydrogen, chlorosilanes, and hydrogen chloride. Chemical Design’s process combines compression, absorption, distillation, ambient adsorption and cryogenic adsorption to purify the hydrogen gas to 99.999% for use in manufacture of electronics grade polycrystalline silicon. The proprietary process recovers over 98% of the vent gases for reuse. Mixed chlorosilanes are recovered as a liquid stream suitable for distillation to trichlorosilane for reuse. Silicon tetrachloride can be converted to trichlorosilane. The hydrogen chloride is recovered with high purity to be reused in a fluid bed reactor to produce trichlorosilane. The process is attractive environmentally because there is no waste streams disposal.