Technical Abstract: An apparatus for the in situ quantification of malodorous compounds from animal wastewater was developed that employed a submersible magnetic stir plate and stir bar sorbtive extraction using polydimethylsiloxane-coated stir bars. Prior to deployment of the apparatus in a hog waste lagoon, experiments were conducted to determine minimum equilibration time as well as the minimum volume of sample needed for external standard calibration of samples. Minimum equilibration time was determined by monitoring loss of preloaded standards from the stir bars while minimum calibration volume was based on the criterion that a spiked standard solution was found not to be significantly depleted upon re-extraction. The samplers were preloaded with standards of compounds that approximated the physical characteristics of target analytes, and deployed in the lagoon with and without stirring. Significantly higher levels of some key malodorous compounds were found in stirred as compared to unstirred samples, while loss of preloaded analytes from stirred samples indicated that these samplers had more nearly reached equilibrium with the environment.