A gas-reaction apparatus for demonstrating how automotive catalysts oxidize hydrocarbon fuel residuals generated by incomplete fuel combustion has been fabricated from readily available components, i.e., a plastic syringe filled with a mixture of butane and air, a platinized fiberglass catalyst in a Pyrex tube, and a plastic syringe containing a small amount of color-change glue. The platinized fiberglass catalyst, removed from a commercially available lighter-fuel-powered hand-warmer, converts the mixture of butane and air into carbon dioxide and water. The generated gases are detected by the color-change glue, which contains an acid–base indicator.