Personal CO 2 bubble: Context-dependent variations and wearable sensors usability

Abstract

High CO 2 concentration in inhaled air has been shown to negatively impact work performance and increase acute health symptoms. As respiratory CO 2 is constantly exhaled, it may not dissipate in surrounding air in absence of adequate air movement and is instead re-inhaled into the airways (breathing in a CO 2 -rich bubble). In this study, we explored the impacts of context-dependent factors such as office activities, desk settings, and personal differences on the inhalation zone CO 2 concentration and on concentrations at a below-neck wearable sensor. We found that all factors significantly impact measurements at both measuring points of our test subjects. Presence of a small portable desk fan was also found to significantly reduce the CO 2 concentration. On average, we observed a 177 ppm reduction in CO 2 concentration when using a fan, which is 25 ppm higher than the background CO 2 measurement (650 ppm). Among 41 test subjects, we found distinct relationships between the inhalation zone CO 2 concentration and the wearable sensor measurements and, by applying a hierarchical clustering algorithm, we found 4 clusters of relationships. While below-neck wearable sensors could be used as an exact measure of inhalation of CO 2 concentration for 29% of the subjects, we identified a boundary point (917 ppm) separating high and low inhalation zone CO 2 concentration measurements.