Gaseous metal or metalloid chloride production streams (1) are subjected to the application of thermal energy in the presence of hydrogen or a surface active material (6) for a time and at a temperature sufficient to reduce the organohalogen compounds but not materially adversely affecting the chloride. Suitable surface active materials include coke, activated carbon and alumina. The metal or metalloid may be for instance, aluminium, titanium, magnesium, molbydenum, tungsten, tantalum, beryllium, boron, zirconium, hafnium, niobium, or silicon. Titanium and magnesium, and especially aluminum, are preferred.