Reduction of hydrogen contents in low Z films coated at room temperature has been systematically investigated to control hydrogen recycling, which is considered as one of key issues to achieve high plasma performance in Large Helical Device (LHD). Within experiments on boron films produced from B10H14 or B2H6 and carbon films from CH4, the hydrogen content is successfully reduced with the increase of the film growth rate by controlling DC glow discharge conditions. These results form an important database for general use of hydrogen reduction in low Z films coated at room temperature.