Trials on the transmission of olfactory information together with audio/visual information are currently being conducted in the field of multimedia. However, continuous emission of a scent creates problems of human adaptation to the lingering olfactory stimuli. During long movie scenes, viewers can not detect an emitted scent continuously. To overcome this problem we applied pulse ejection to repeatedly emit scent for short periods of time to ensure the olfactory stimuli do not remain in the air to cause adaptation. This study presents the decision procedure for the ejection interval ?t required while considering the olfactory characteristics of subjects. The developed method provided the user with an olfactory experience over a long duration, avoiding adaptation.