An evaluation of the risk of airborne transmission of COVID ‐19 on an inter‐city train carriage

Abstract

Experiments were conducted in an UK inter‐city train carriage with the aim of evaluating the risk of infection to the SARS‐CoV‐2 virus via airborne transmission. The experiments included in‐service CO2 measurements and the measurement of salt aerosol concentrations released within the carriage. Computational fluid dynamics simulations of the carriage airflow were also used to visualise the airflow patterns, and the efficacy of the HVAC filter material was tested in a laboratory. Assuming an infectious person is present, the risk of infection for a 1‐h train journey was estimated to be 6 times lower than for a full day in a well‐ventilated office, or 10–12 times lower than a full day in a poorly ventilated office. While the absolute risk for a typical journey is likely low, in the case where a particularly infectious individual is on‐board, there is the potential for a number of secondary infections to occur during a 1‐h journey. Every effort should therefore be made to minimize the risk of airborne infection within these carriages. Recommendations are also given for the use of CO2 sensors for the evaluation of the risk of airborne transmission on train carriages.

Predicting aerosol transmission in airplanes: Benefits of a joint approach using experiments and simulation

“…This especially happens in proximity to a body which heats the surrounding air. The reason for this effect is that the density of air changes with the temperature which is modeled by the ideal gas law Equation (5). The thermal conductivity 𝜆 air = 0.0262 W∕(m K) and specific heat capacity c p,air = 1000 J∕(kg K) of the air are assumed to be constant.…”

“…With a special focus on indoor environments, research in this direction has been used to estimate the appropriateness of different health and safety measures (e.g., Reference 1). Many experimental studies have been conducted to investigate particle transmission and the efficacy of face masks (e.g., References 2–5). To make faster predictions, various numerical simulation models have also been proposed.…”

Airborne transmission risks of tuberculosis and COVID-19 in schools in South Africa, Switzerland, and Tanzania: Modeling of environmental data

“…where D is the number of diseased cases, S is the number of susceptibles, � f is the time-weighted average fraction of rebreathed air (in %), I is the number of infectious students; n is the total number of students in the room, q is the rate of infectious doses (quanta) generated by infectious individuals (in quanta h -1 ), and t is the duration of exposure (in h). We computed the average rebreathed air fraction as � f ¼ ð � C À C O Þ=C a using the average of the indoor CO 2 measurements (C in parts per million [ppm]) and assuming a CO 2 level of C o = 400 ppm in the outdoor air [20,22,[27][28][29][30] as well as C a = 31,500 ppm in the exhaled air [25,31].…”

“…Third, we assessed the impact of assuming an outdoor CO 2 level of C o = 600 ppm instead of C o = 400 ppm in each countries. Although many studies use C o = 400 ppm [20,22,[27][28][29][30], the outdoor CO 2 levels can be C o = 500 ppm or higher in urban areas, especially in the early morning, mainly due to traffic-related emissions [20].…”

Active Air Monitoring for Understanding the Ventilation and Infection Risks of SARS-CoV-2 Transmission in Public Indoor Spaces

“…The potential risk of airborne disease transmission including SARS-CoV-2 is often estimated employing a fully mixed standard atmospheric box model/Wells-Riley model [33]. We assume that, initially, no virus was present in the space, the viral load builds over the period, and for the entire duration of risk estimation, the infected and susceptible individuals always occupy the space, and for this scenario, the probability of infection can be estimated using Equation (3).…”