Indoor odor exposure effects on psycho-physiological states during intellectual tasks and rest

The responses of five human subjects to two indoor airborne odors (mint and cypress) were examined to determine the effect of perceived air quality and odor type and duration on several psycho-physiological variables during periods of rest and while performing intellectual tasks. An olfactometer system was installed in a climate chamber at the University of Tokyo, with the nozzle located on a desk just to the right of the task-performance screen. The odor concentration presented to the subject was adjusted to keep the perceived odor intensity constant at level 2 (weak) as established in a pretest. Subjects performed a simulated office task, 12 min of Sudoku (number placing puzzle), or rested for 7 min. The task and the rest periods were repeated six times each (except for first and last rests) during one day's exposure. Odor exposures during tasks and rest involved one of the two odors for either a short or long period. During the 3 min between a task and rest, subjects rated their perceptions of odor intensity, degree of odor preference (enjoyment, pleasing quality), comfort, indoor air satisfaction, effect on work efficiency, and several other affective responses. Heart rate variability was continuously monitored by electrocardiographs to assess the activity of the autonomic nervous system. Exposure to a preferred odor may improve comfort, satisfaction, and mood, as well as increase self-reported work efficiency; it may also enhance the activity of the parasympathetic system. Sensitivity to a preferred odor was higher at rest than during a task. The exposure time that produces a positive effect on a subject's physiological responses differs with activity level, being 1 min during work and 10 min when at rest.