We’ve known for a long time that public transport presents one of the highest-risk environments when it comes to COVID-19 transmission. However, with the recent trend of individuals taking carbon dioxide monitors through their daily lives, the true dangers of public transport have been exposed.

Currently, there is no way to monitor the number of COVID-19 or even respiratory particles in the air. This means we have no direct way to measure the risk of contracting COVID-19 via airborne particles. As such, many have turned to monitoring CO2 as CO2 concentrations act as a proxy for the risk of catching COVID. We discussed this in more detail in our recent article on the dangers of carbon dioxide.

While high concentrations of carbon dioxide carry risks, the big focus recently is on carbon dioxide acting as an indication of COVID-19 danger as studies have shown that as the carbon dioxide concentration doubles, so too do the chances of catching COVID-19. This has led to some rather interesting findings, especially concerning public transport and flights.

Some Twitter users have found carbon dioxide concentrations over 1600ppm on trains (source), while others have found concentrations as high as 2400ppm (source) and beyond. At 2400ppm, our chances of catching COVID-19 are approximately six times higher than in ambient air (where the CO2 concentration is around 400ppm).

However, this issue is not limited to trains. During flights, some Twitter users have found CO2 concentrations to exceed 2000ppm (source). This issue is far from consolidated, as many users have reported similarly high (source) or even higher readings across their flights. 

With so many people collecting data on air quality during day-to-day life, the low air quality on public transport has become more evident than ever. Alone, carbon dioxide can be very detrimental to our health. However, when combined with the increased transmission of COVID, these exceedingly high concentrations are not something we should accept.

More than anything, they exemplify the importance of continued mask wearing on public transport and during flights. While donning a mask won’t limit the CO2 we breathe in, it will give us a far lower chance of catching COVID-19 and other viruses in these dangerous situations.