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For Immediate Release

Wendy Powers, Iowa State University, (515) 294-1635,
Rachel E. Martin, Iowa Beef Center, (515) 294-9124,
Brian Rumsey, Iowa Beef Center, (515) 294-2333,

ISU Research Seeks To Measure Livestock Odor Levels

AMES, Iowa - Gaseous emissions from livestock and poultry facilities have received significant attention within the industry, but they are still not fully understood. Recent research conducted at Iowa State University has sought to increase understanding by clarifying which specific compounds contribute to odors and how environmental conditions and distance affect odors. With possible new state regulations for gaseous emissions in the future, understanding them is becoming more important than ever.

For the study, air samples were collected from Iowa dairy, poultry, and swine facilities during two ten-week periods, one from May through July 2001, and the other from May through August 2002. The air samples were transported to Iowa State University for analysis. Some on-site analysis was also performed.

Odor was measured by determining how much unscented air had to be mixed with the collected air samples in order to make the odor almost unnoticeable. Of the gases monitored, hydrogen sulfide was found to be most correlated to odors.

The study also found that higher temperatures and higher humidity caused stronger odors, and that with other conditions equal, odors were stronger on sunny days than on cloudy days.

At the study sites, at distances of 50 meters or more from the facilities, the hydrogen sulfide measurements were generally within the limits that may become law. This suggests that, while it is worthwhile to know hydrogen sulfide levels, the operations followed in this study would not, on average, have exceeded the proposed standards.

Through the data obtained in the study, mathematical formulas were determined to predict odor and gas concentrations under various conditions. These formulas can be found in the full research report.

Predicting odors remains somewhat uncertain, though. “We had two facilities right next to each other, managed by the same people with the same practices," said Wendy Powers, associate professor of animal science and lead investigator in the study. “We would have thought they would have had similar odor and gas levels, but one was much higher than the other."

To read more about this research, visit


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