Accurate evaluation of inhalation exposure based on CFD predicted concentration in the breathing zone towards personalized and smart control

Abstract

Considering pollutants sourced from one's own exhaled air and skin as well as ambient air, this study adopts CFD technology to explore accurate evaluation method of inhalation exposure based on the pollutant concentration in the breathing zone. To do so, the concentration data extracted from the surfaces of mouth/nose openings and various sampling points close to mouth/nose openings is analyzed. The distribution of exhaled pollutants on one's own face is subsequently revealed and the re-inhalation ratio is quantified. If only point data is available (e.g., experimental context), the inhalation exposure to one's own exhaled pollutants can be evaluated based on the data at the center of the upper lip when inhaled through the mouth and at a location of 0.005 m away from the center of the nose openings when inhaled through the nose. If surface data is available (e.g., numerical context), the data on the whole mouth/nose openings should be used to evaluate the exposure. The distribution of exhaled pollutant concentration on one's own face changes periodically and asymmetrically over time. Based on the data obtained on face, the inhalation exposure to pollutants from one's own exhaled air would be underestimated. Depending on breathing mode, the re-inhalation ratio is mostly in a range of 0.3–1.0%. These findings can contribute to a more accurate evaluation of inhalation exposure and provide information for the development of personalized air quality control systems and smart wearable devices.