Parking Under the Sun: Solar Heating As a Strategy for Passively Disinfecting COVID-19 in Passenger Vehicles During Warm-Hot Weather

Abstract

Shared passenger vehicles (taxis, Uber, other drivers-for-hire services) are common in daily transportation. The confined, enclosed space as well as commonly touched surfaces in those sub-environments pose elevated risks of COVID-19 transmission via respiratory, contact, and airborne routes. Current regulatory guidelines rely on voluntary acts from passengers on wearing face coverings while require cleaning and disinfecting by drivers, with gaps left between drivers’ shifts and transmission from non-symptomatic individuals. A labor-intensive procedure, repetitive manual cleaning and disinfecting may present a nuisance for some drivers and can be ineffective in areas that are difficult to access. There is an urgent need to evaluate other strategies to mitigate the risks of COVID-19 infection in passenger vehicles. Since the persistence of the novel coronavirus is sensitive to ambient temperatures, and that inactivation could be achieved within minutes to half an hour at 50–60 °C, solar heating – by parking vehicles under direct sunlight with doors and windows closed – presents a viable strategy for passively disinfecting COVID-19 in vehicle interiors during warm-to-hot weather. To demonstrate this approach, we measured the temperatures in a white compact-size sedan left in a parking lot under direct sunlight. Air temperatures increased rapidly in the cabin during the first 30–40 min, followed by steady increases in the next hour, then plateaued after reaching 52–57 °C at 90 min. Spatial variations (5 ± 1 °C) were found at four diagonal points in the front and back seat at the breathing and knee heights of an average seated adult, with higher temperatures registered in the front and the upper zone. The results supported our hypothesis that hot air generated by solar heating in enclosed objects provides a viable means of thermal inactivation for COVID-19, in a passive manner that does not involve chemical use, laborious work, or waste discharge to surrounding environments.