The fundamental behaviour of AC arc plasma confined by polymer materials was experimentally investigated using a simplified low-voltage test circuit breaker. The arc voltage and arc current were measured to study the influence of polymer and metallic vapour contamination on the arc plasma. Spectroscopic observation and high-speed video measurement were also conducted to determine the behaviour of quenching arc plasmas. These experiments found that the peak value of post-arc current largely depends on the polymer and electrode materials contaminated, and that higher electron density may provide a higher post-arc current peak.