Improving environmental odor measurements: comparison of lab-based standard method and portable odor measurement technology

Current standard odor measurement methods are lab-based and require substantial investment in hardware, sample collection, training, and maintenance. Odor samples must be collected in the field using bags and brought to the lab to test. This can be a time-consuming process, with the possibility of the sample loss. The actual odor measurements are based on dilution olfactometry, embodied in the AC’SCENT® International Olfactometer, following the ASTM E679-04 standard. In recent years a portable olfactometer, the Scentroid SM100i, has been developed for odor measurements. The portable olfactometer has many advantages over lab-based standard method, especially the lower cost-per-sample. However, very little is known about the performance and reliability of portable olfactometer where the dilutions are controlled with orifices in metallic plates. It is important to evaluate the Scentroid SM100i accuracy to determine the usefulness of using it as a comparable technology for odor measurements. The main objective of this research is to compare the performance of the lab-based ASTM E679-04 method with portable odor measurement technology. Specific objectives include: (1) determining the accuracy of the dilution ratios specified by the manufacturer of both the AC’SCENT International Olfactometer and the Scentroid SM100i; (2) comparing results between olfactometers using n-butanol, a commonly used standard gas in the olfactometry field, and (3) determining the accuracy of odor measurement using real odor samples collected from livestock farms in Iowa. The AC’SCENT olfactometer had an average percent error between the factory specifications and measured dilution ratios of 5.23% compared with 14.1% for Scentroid SM100i (using plate i-2 with dilution range most comparable to the AC’SCENT olfactometer). The use of other dilution plates resulted in average percent errors ranging from 9.68% to 25.31%. The Scentroid SM100i deviated from the manufacturer specifications for flowrates and dilution ratios, but these flowrates were generally consistent with each dilution setting. Overall, the Scentroid SM100i overestimated the odor concentrations with the mean difference of 22.9% (ranging from 0.95% to 93.34%). When the post-measurement adjustment using dilution correction was made, the mean percent average difference was 11.8%.This article is published as Maurer, Devin L., Alexandrea M. Bragdon, Brandon C. Short, Heekwon Ahn, and Jacek A. Koziel. "Improving environmental odor measurements: comparison of lab-based standard method and portable odor measurement technology." Archives of Environmental Protection 44, no. 2 (2018): 100-107. DOI: 10.24425/119699. Posted with permission.</p