In 2020, East Asia was officially declared free of foot-and-mouth disease, which means that the number of piggeries in the region will increase. Piggeries produce ammonia gas that must be managed. In this study, we propose a decomposition system that automatically tracks ammonia concentration and employs ozone and water mist to decompose ammonia gas. The key components of the system are a ceramic plate-type ozone generator, an ammonia gas detector (e.g., MQ-137), and an ammonia tracking circuit. The oxygen generator consists of two parts, namely, the circuit architecture and the oxygen supply. The circuit architecture consists of an AC power supply, a standby power supply, an electromagnetic interference filter, a power factor correction circuit of a boost converter, a full-bridge parallel resonance converter, a full-bridge drive circuit, and a ceramic plate. The system operates by inputting ozone of varying concentrations into the washing basket to mix with mist and ammonia gas. A voltage signal from the ammonia tracking circuit is used as the basis for adjusting the operating frequency of the ozone generator and the resonance voltage. The ozone generator can output four power levels (25, 50, 75, and 100%), which correspond to four different ozone concentrations. The experimental results demonstrated that decomposition was most effective when the ozone generator output power was 100%.