Monitoring SARS-CoV-2 Risk with CO2. The Importance of Ventilation, Masks, and Vaccinations.

Authors

Preston Betz, Southern Methodist UniversityFollow

Contributor

Robert T. Gregory

Subject Area

Health Sciences, Immunology, Public Policy

Abstract

To assess airborne pathogen infection risk, concentrations of interior carbon dioxide and changes in relative humidity serve as proxies for human respiration products. Yanes and Yapp, 2010, demonstrated that interior air carbon dioxide concentrations and ¹³C/¹²C ratios display a two-component mixing relationship between respiration carbon dioxide which is highly concentrated (>100x atmospheric) in respiration air CO₂ at >40,000 ppm compared with ambient air (~410 ppm). In the absence of combustion carbon dioxide, the concentration of carbon dioxide, in an interior space, depends on the rate of respiration CO₂ addition relative to the amount of fresh atmosphere mixed back into the air circulation system. The number of occupants and the proportion of outside air introduced to determine a series of steady-state room concentrations punctuated by transient CO₂ concentrations that follow first-order rate laws with linear trends in plots of ln(f) vs. time where f tracks the progression of concentrations between unoccupied and occupied states of a building. Previous studies have shown several school classrooms achieve CO₂ concentrations 2 to 5 times atmospheric, with buildup times on minute to hour timescales depending on the size of the room and number of occupants. Preliminary data show that removal time scales exceed rise timescales ~1/2 of the time and are at least ten to thirty minutes longer than the steady-state rise times, i.e., the transmission of pathogens can occur before their removal by the filtration system. Using American Society of Heating Refrigeration and Air-Conditioning Engineering (ASHRAE) standards and isotopic ratio measurements measured ppm concentrations of CO₂ transform into percentages of classroom respiration CO₂ whichtypically exceeds 40% and can be >60% inhaled respiration carbon dioxide. CO₂ can be translated into infection risk with increasing CO₂ values correlating to higher risk of infection and a decrease in overall exposure time prior to an infection.

Degree Date

Spring 5-2022

Document Type

Thesis

Degree Name

M.S.

Department

Earth Sciences

Advisor

Robert T. Gregory

Second Advisor

Crayton J. Yapp

Third Advisor

Matthew Hornbach

Number of Pages

208

Format

.docx

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Recommended Citation

Betz, Preston, "Monitoring SARS-CoV-2 Risk with CO2. The Importance of Ventilation, Masks, and Vaccinations." (2022). Earth Sciences Theses and Dissertations. 25.
https://scholar.smu.edu/hum_sci_earthsciences_etds/25