Ambient hydrogen sulfide concentrations were monitored for several months at the property line of a wean-to-finish swine production facility. Data was analysed to determine apparent influences of slurry characteristics, wind speed, and time of day. It was also analysed to evaluate the apparent potential effectiveness of a commercial manure additive, limited aeration, and a permeable geotextile/straw cover on reducing ambient hydrogen sulfide levels. The addition of the manure additive, combined with warm weather and 41 days of aeration in late summer, apparently reduced volatile fatty acids, sulfide and BOD in the lagoon slurry and also the ambient hydrogen sulfide concentrations. The actual effect could not be determined due to the absence of a control lagoon. Nighttime concentrations were twice as high as daytime concentrations. Mean ambient hydrogen sulfide concentrations with the cover were only 13% of mean concentrations before the cover was installed.