{HEAD ~ electrical heating wire elements} mounted to said housing within said chamber, said heating wire elements being subject to damage in a reduction atmosphere, and exposed to {TAIL ~ a central portion} of said chamber, said electrical heating elements having an energized and a deenergized state, said chamber being heated when said electrical heating elements are energized 
exposed to
{ HEAD ~ electrical heating wire elements } mounted to said housing within said chamber , said heating wire elements being subject to damage in a reduction atmosphere , and exposed to { TAIL ~ a central portion } of said chamber , said electrical heating elements having an energized and a deenergized state , said chamber being heated when said electrical heating elements are energized
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