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. 2022 Feb 2;7(1):19-30.
doi: 10.20411/pai.v7i1.493. eCollection 2022.

SARS in Cars: Carbon Dioxide Levels Provide a Simple Means to Assess Ventilation in Motor Vehicles

Muhammed F Haq  1 , Jennifer L Cadnum  1 , Matthew Carlisle  1 , Michelle T Hecker  2   3 , Curtis J Donskey  3   4
Affiliations

SARS in Cars: Carbon Dioxide Levels Provide a Simple Means to Assess Ventilation in Motor Vehicles

Muhammed F Haq et al. Pathog Immun. .

Abstract

Background: Poorly ventilated enclosed spaces pose a risk for airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses. Limited information is available on ventilation in motor vehicles under differing driving conditions.

Methods: We conducted carbon dioxide measurements to assess ventilation in motor vehicles under varying driving conditions with 2 to 3 vehicle occupants. During routine driving, carbon dioxide produced by the breathing of vehicle occupants was measured inside 5 cars and a van under a variety of driving conditions with or without the ventilation fan on and with windows open or closed. Carbon dioxide readings above 800 parts per million (ppm) were considered an indicator of suboptimal ventilation.

Results: Carbon dioxide levels remained below 800 ppm in all vehicles if the ventilation fan was on and/or the windows were open while parked or during city or highway driving. With the ventilation system set on non-recirculation mode, carbon dioxide levels rose above 800 ppm in all vehicles when the fan was off and the windows were closed while parked and during city driving, and in 2 of the 6 vehicles during highway driving. With the ventilation system set on recirculation mode, carbon dioxide rose above 800 ppm within 10 minutes in all vehicles tested.

Conclusion: Carbon dioxide measurements could provide a practical and rapid method to assess ventilation in motor vehicles. Simple measures such as opening windows, turning on the fan, and avoiding the recirculation mode greatly improve ventilation.

Keywords: COVID-19; SARS-CoV-2; Ventilation; aerosol; carbon dioxide; transmission.

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Conflict of interest statement

C.J.D has received research grants from Clorox, Pfizer, and PDI. All other authors report no conflicts of interest relevant to this article.

Figures

Figure 1.
Figure 1.
Parked Vehicles. Carbon dioxide levels in the parked motor vehicles under 3 different ventilation conditions. The 5 cars had 2 occupants and the van had 3 occupants. Ventilation conditions included 1 front window fully open with fan off, windows closed with fan on at medium speed, and windows closed with fan off. Carbon dioxide readings above 800 parts per million were considered an indicator of suboptimal ventilation.
Figure 2.
Figure 2.
Highway driving on recirculation mode. Carbon dioxide levels in 3 cars when driven on the highway with the fan on and the ventilation system set on recirculation mode. *, 1 front window partially or fully opened. Carbon dioxide readings above 800 parts per million were considered an indicator of suboptimal ventilation.
Figure 3.
Figure 3.
Carbon dioxide levels in motor vehicles driven under differing ventilation conditions. The 5 cars had 2 occupants and the van had 3 occupants. Windows were closed unless otherwise specified. Windows open indicates that 1 front window was partially or fully open. Carbon dioxide readings above 800 parts per million were considered an indicator of suboptimal ventilation.
Figure 4.
Figure 4.
Measured airflow from the front vents for 3 test vehicles under varying driving conditions.
See this image and copyright information in PMC

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