Six feet physical distance required to avoid the Covid-19 virus an infected person may shed when breathing or speaking might not help indoors, say researchers.
The engineering team at the University of Pennsylvania found that indoor distances of two metres might not be sufficient enough to curb transmission of airborne aerosols.
Aerosols travelled farther and more quickly in rooms with displacement ventilation, where fresh air continuously flows from the ground and pushes old air to an exhaust vent near the ceiling.
This is the sort of ventilation installed in most residential homes, and it may result during a human breathing zone concentration of viral aerosols seven times above mixed-mode ventilation systems.
Many commercial buildings use mixed-mode systems, which incorporate outside air to dilute the indoor air and end in better air integration — and tempered aerosol concentrations, consistent with the researchers.
“Our study results reveal that virus-laden particles from an infected person’s talking — without a mask — can quickly visit another person’s breathing zone within one minute, even with a distance of two metres,” said Donghyun Rim, professor of engineering .
“This trend is pronounced in rooms without sufficient ventilation. The results suggest that physical distance alone isn’t enough to stop human exposure to exhaled aerosols and will be implemented with other control strategies like masking and adequate ventilation,” Rim added. The findings are available online within the journal Sustainable Cities and Society.
The researchers examined three factors: the quantity and rate of air ventilated through an area , the indoor airflow pattern related to different ventilation strategies and therefore the aerosol emission mode of breathing versus talking.
“This is one among the surprising results: Airborne infection probability might be much higher for residential environments than office environments,” Rim said. “However, in residential environments, operating mechanical fans and stand-alone air cleaners can help reduce infection probability.”
According to Rim, increasing the ventilation and air mixing rates can effectively reduce the transmission distance and potential accumulation of exhaled aerosols, but ventilation and distance are the sole two options in an arsenal of protective techniques.