Exhaled CO2 as COVID-19 infection risk proxy for different indoor environments and activities

Abstract

AbstractCO2 is co-exhaled with aerosols containing SARS-CoV-2 by COVID-19 infected people and can be used as a proxy of SARS-CoV-2 concentrations indoors. Indoor CO2 measurements by low-cost sensors hold promise for mass monitoring of indoor aerosol transmission risk for COVID-19 and other respiratory diseases. We derive analytical expressions of CO2-based risk proxies and apply them to various typical indoor environments. The relative infection risk in a given environment scales with excess CO2 level, and thus keeping CO2 as low as feasible in a space allows optimizing the protection provided by ventilation. We show that the CO2 level corresponding to a given absolute infection risk varies by over 2 orders of magnitude for different environments and activities. Although large uncertainties, mainly from virus exhalation rates, are still associated with infection risk estimates, our study provides more specific and practical recommendations for low-cost CO2-based indoor infection risk monitoring.Table of Contents Graphic