The emphasis on H2S emissions has increased in recent years due to significant levels being emitted by some single-bed three-way catalyst equipped vehicles. Studies to identify the mechanisms of H2S formation have suffered due to the sample time dependent wet chemical methods used for H2S analyses. A simple but effective dilution and sample system has been developed for use with a commercially available gold film H2S analyzer. This provides semi-continuous H2S analyses directly from the engine exhaust and has proven to be an excellent tool for defining the effects of vehicle operating conditions on H2S formation. Engine dynamometer studies have been used to investigate the effects of air/fuel, catalyst inlet temperature, and transient duration on sulfur storage and release over single-bed three-way catalyst systems.