Abstract: A method of removing surface carbon contamination from polycrystalline silicon comprises providing a polycrystalline silicon feed stream having surface carbon contamination, subjecting the polycrystalline silicon to a high velocity fluid selected from gas, gas/liquid mixtures, gas/solid mixtures and gas/solid/liquid mixtures to form a product stream comprising polycrystalline silicon having surface carbon in an amount of less than 200 parts per billion by weight based on weight of the polycrystalline silicon product and/or a reduction in surface carbon contamination of at least 20%. A system for conducting the method comprises an enclosure, a conveyer for moving a polycrystalline silicon feed stream through the enclosure, at least one stream of a high velocity fluid passing through outlets in the enclosure and directed at the feed stream, an ionizing source in the enclosure or integrated with the at least one stream of high velocity fluid, and an exhaust system for the enclosure.

Abstract: A sound barrier cover for a compressor unit which has a housing provided by a substantially continuous wall which provided with a plurality of access ports therethrough. The barrier cover has first and second shell sections configured to lie close to the housing wall and substantially envelope the same wherein the shell sections are configured to provide two substantially longitudinally oriented halves each having sound absorbing material affixed to its inner surface. These halves have perimeters with portions thereof formed with mating tongue and groove structure and carry cooperating components of snap-fastener devices in close proximity to the perimeters. These snap-fastener devices are adapted to hold the perimeters in contact with each other and with the sound absorbing material in resilient contact with the housing.