the present invention relates to the simultaneous manufacture of difluoromethane and 1 , 1 , 1 , 2 - tetrafluoroethane by pyrolysis of chlorodifluoromethane in the presence of hydrogen , working at a temperature above 500 ° c . in the absence of any catalyst or metal surface . depending on the operating conditions chosen , this process also makes it possible predominantly to manufacture either f134a or f32 .