Expanded olfactometer for measuring reaction time to a target odor during background odor presentation

Current olfactometers can insert a target odor into the flow of odorless air as a pulse (i.e., replace odorless air with target odor for a very short time), but no previously designed olfactometer can insert a pulse of target odor into a flow of background odor (i.e., replace background odor with target odor for a very short time). To measure reaction time to a target odor during presentation of a background odor, we developed an expanded olfactometer by adding an attachment to an existing olfactometer. We conducted three experiments to evaluate the performance of the expanded olfactometer. Additionally, four volunteers participated in trial measurement of reaction time for detection of the target odor under background odor and odorless air conditions using the expanded olfactometer. We did not observe a significant difference in gas onset time or rise time of the target odor between background and odorless air conditions. Additionally, the gas onset time and rise time of the target odor were on the order of milliseconds, whereas the gas onset time and rise time of the background odor were on the order of seconds. The reaction time was marginally significantly longer under the background odor condition than the odorless air condition. We did not observe a significant difference in gas onset time or rise time of the target odor between the existing olfactometer and our expanded olfactometer. We succeeded in developing an attachment capable of inserting a target odor into a flow of background odor. Our results revealed that performance related to the presentation of the target odor was comparable between the existing and expanded olfactometers. To more rigorously examine the effect of background odor on detection speed of target odor, we intend to increase the number of participants in the near future.