A recent report in New Zealand found that carbon dioxide levels in public transportation settings in the country are typically poor, representing low ventilation. Furthermore, these higher concentrations of carbon dioxide act as a proxy measure for COVID-19 transmission risk.
To gather data for the report, a team used a consumer-grade carbon dioxide monitor (the Aranet4 Home) to gather carbon dioxide concentration data on 30 bus trips and 15 train trips in three different cities. The data was gathered during the autumn and winter months.
As expected, the study found that carbon dioxide levels steadily rise as occupancy increases, and there was a statistically significant difference in carbon dioxide levels on buses and trains with higher and lower occupanc.
The findings of the report are telling, with buses and trains with ≥ 50% occupancy having poor ventilation 94% and 77% of the time, respectively. Worryingly, even with this poor ventilation, very few passengers were masked (2.6%-10.6%). These low masking rates are concerning considering the high transmission chance of airborne illnesses in these settings.
So, what can we conclude from the findings of this report? While it was isolated to a relatively small sample of public transport in New Zealand, the findings can be applied in public transport settings all around the world. Firstly, better ventilation is needed on trains and buses. Secondly, individual actions such as mask-wearing are still as important as ever.