\Decomposition of low concentrations of covalent chlorides and fluorides (CCl4, SF6, CHF3, CHClF2) in N by non-thermal plasma was investigated. Specifically, the influence of hydrogen and of in-situ Ca(OH)(2) absorbent on the decomposition were determined in terms of the decomposition ratio of the gases, which form inorganic halide from free halide species. It was found that the decomposition ratios of SF6 and CCl4 with 2% H-2 in N-2 were higher than those in N-2 atmosphere. HCl, Cl-2, HF and F-2 were regarded as the major products formed from the decomposition of the gases in N-2 atmosphere. With the combination of non-thermal plasma and in-situ absorption using a layer of Ca (OH)(2) coated on the surface of the grounding electrode, the decomposition ratio increased and products such as HCl, Cl-2, HF and F-2 were effectively scavenged. It was demonstrated that the Ca (OH)(2) absorbent played an effective role in capturing the unwanted intermediates in the plasma reactor.