Researchers from the University of Cambridge and Imperial College London have quantified the role of ventilation in Covid-19 infection spread.
They have found that in poorly-ventilated spaces, the virus spreads further than two meters in seconds, and is far more likely to spread through prolonged talking than through coughing.
The results, reported in the journal Proceedings of the Royal Society A and Science Daily, revealed that social distancing measures alone do not provide adequate protection from the virus.
They further stressed the importance of ventilation and face masks in order to avert the spread of Covid-19.
The researchers employed mathematical models to show how SARS-CoV-2 spreads in different indoor spaces, depending on the size, occupancy, ventilation, and whether masks are being worn.
These models are also used to establish a free online tool — Airborne.cam — which helps users understand how ventilation and other measures affect the risk of indoor transmission, and how that risk changes over time.
Findings
The researchers found that when two people are in a poorly-ventilated space and neither is wearing a mask, prolonged talking is far more likely to spread the virus than a short cough.
They noted that it only takes a matter of seconds for aerosols to spread over two meters when masks are not worn, implying that physical distancing in the absence of ventilation is not sufficient to provide safety for long exposure times.
"Our knowledge of airborne transmission of SARS-CoV-2 has evolved at an incredible pace when you consider that it's been just a year since the virus was identified," said first author Dr. Pedro de Oliveira from Cambridge's Department of Engineering.
They also showed through their mathematical models that the infection risk after speaking for one hour in a typical lecture room was high, but the risk could be decreased significantly with adequate ventilation.
Based on their models, the researchers have now built Airborne.cam, a free, open-source tool. The tool can be used by those managing public spaces, such as shops, workplaces and classrooms, in order to determine whether ventilation is adequate.
The tool is already in use in several academic departments at the University of Cambridge. The tool is now a requirement for any higher-risk spaces at the University, enabling departments to easily identify hazards and control-measure changes needed to ensure aerosols are not allowed.