Correlation of Respiratory Aerosols and Metabolic Carbon Dioxide

Niklas Kappelt, Hugo Savill Russell, Szymon Kwiatkowski, Alireza Afshari and Matthew Stanley Johnson
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Niklas Kappelt: Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark
Hugo Savill Russell: Airlabs, Nannasgade 28, 2200 Copenhagen, Denmark
Szymon Kwiatkowski: Airlabs, Nannasgade 28, 2200 Copenhagen, Denmark
Alireza Afshari: Department of the Built Environment, Division of Sustainability, Energy and Indoor Environment, Aalborg University, 2450 Copenhagen, Denmark
Matthew Stanley Johnson: Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark

Sustainability, 2021, vol. 13, issue 21, 1-11

Abstract: Respiratory aerosols from breathing and talking are an important transmission route for viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Previous studies have found that particles with diameters ranging from 10 nm to 145 μm are produced from different regions in the respiratory system and especially smaller particles can remain airborne for long periods while carrying viral RNA. We present the first study in which respiratory aerosols have been simultaneously measured with carbon dioxide (CO 2 ) to establish the correlation between the two concentrations. CO 2 concentrations are easily available through low-cost sensors and could be used to estimate viral exposure through this correlation, whereas source-specific aerosol measurements are complicated and not possible with low-cost sensors. The increase in both respiratory aerosols and CO 2 was linear over ten minutes in a 2 m 3 chamber for all participants, suggesting a strong correlation. On average, talking released more particles than breathing, with 14,600 ± 16,800 min −1 (one- σ standard deviation) and 6210 ± 5630 min −1 on average, respectively, while CO 2 increased with 139 ± 33 ppm min −1 during talking and 143 ± 29 ppm min −1 during breathing. Assuming a typical viral load of 7 × 10 6 RNA copies per mL of oral fluid, ten minutes of talking and breathing are estimated to produce 1 and 16 suspended RNA copies, respectively, correlating to a CO 2 concentration of around 1800 ppm in a 2 m 3 chamber. However, viral loads can vary by several orders of magnitude depending on the stage of the disease and the individual. It was therefore concluded that, by measuring CO 2 concentrations, only the number and volume concentrations of released particles can be estimated with reasonable certainty, while the number of suspended RNA copies cannot.

Keywords: respiratory aerosols; carbon dioxide; airborne transmission; indoor air quality; COVID-19 (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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