The goal of work reported here was to assess the potential for early detection of acid gas in case of leakage into overlying aquifers at Zama. Breakthroughs of acid gas at producing wells at other acid gas disposal sites in Alberta indicated that CO2 will arrive first at a producing well, ahead of H2S, although the two gases are injected together. From a monitoring point of view, the implication is that the earlier arrival of CO2, even if not accompanied by H2S, should signal leakage of acid gas from the storage reservoir. Accordingly, an experimental program was set up under contract at Hycal Energy Research Laboratories Ltd. in Calgary to test the hypothesis that the partitioning of the two gases and different arrival time at the producing well are due to different solubility of the two gases in water.