A dynamic dilution-to-threshold odour measurement method was used to evaluate changes in odour level downwind from an on-farm anaerobic liquid swine manure tank during short-term aeration. Air samples were collected at intervals for 24 h after aerator start-up and analyzed by a five-member panel. It was found that the odour threshold of the gases being emitted from the manure tank during aeration was reduced by about two orders of magnitude in 3.5 h. Strong odour samples collected in polyvinyl fluoride plastic bags can be stored for 48 h before threshold analysis without a significant change occurring in the odour threshold.