A system for chemical vapor densification includes a reaction chamber having an inlet and outlet; a trap; a conduit fluidly coupled between the outlet of the reaction chamber and the trap; a cryogenic cooler fluidly coupled to the trap though a frustoconical conduit; a first exit path from the cryogenic cooler that vents hydrogen gas to an exhaust; and a second exit path from the cryogenic cooler that recirculates silane and hydrocarbon-rich gas back to the inlet of the reaction chamber—and a related method places a substrate in the reaction chamber; establishes a sub-atmospheric pressure inert gas atmosphere within the reaction chamber; densifies the substrate by inputting virgin gas into the reaction chamber; withdraws effluent gas from the reaction chamber; extracts silane and hydrocarbon-rich gas from the effluent gas; and recirculates the silane and hydrocarbon-rich gas back to the reaction chamber.