Coronavirus-infected droplets can evaporate faster on warm, humid days above 85F, but viral particles can travel up to 13 FEET without wind, research finds.
- Health officials have recommended people at a social distance by staying six feet apart to prevent the coronavirus from spreading
- Researchers looked at how long airborne droplets can stay in the air, how far they can travel, and whether the size of the droplets determines their survivability
- They discovered that droplets can evaporate in conditions with temperatures around 86F and humidity above 50%
- On days without wind, breathing droplets can travel between 8 and 13 feet
Since the coronavirus pandemic, we have all been told to distance ourselves socially by standing or sitting six feet (or two meters) from strangers.
But a new study suggests that this distance may not be far enough to prevent virus transmission.
Researchers found that infected drops can travel up to 13 feet if not even a wind blows.
However, these drops from people who cough or sneeze can evaporate faster at high temperatures and humidity.
The International Team – from the University of Toronto in Ontario, Canada; Indian Institute of Science in Bengaluru, India; and University of California Los Angeles – says the findings clarify “the role of the environment in infection spread via respiratory drops.”
Researchers found that coronavirus-infected droplets can evaporate in a state with temperatures around 86F and humidity above 50%. Pictured: People gather in Central Park during the ongoing Coronavirus pandemic on May 10
On days without wind, breathing droplets can travel between 8 and 13 feet. Pictured: journalists in the stands at the English Premier League football match between Aston Villa and Chelsea at Villa Park in Birmingham, England, June 21
For the study, published in the journal Physics of liquidsthe team developed a mathematical model on the aerodynamics and evaporation characteristics of respiratory droplets.
They then compared drops ejected by an infected person to those of a healthy person.
About 3,000 drops are expelled by a single cough, many of which spread in different directions.
Up to 40,000 drops can be expelled during a sneeze.
“The size of the droplet cloud, the distance it travels and the life span of the droplet are therefore all important factors that we have calculated while maintaining mass, momentum, energy and species,” said Dr. Swetaprovo Chaudhuri, associate professor of propulsion and energy conversion at the University of Toronto Institute for Aerospace Studies
The team then used the model to calculate how long the air droplets can stay in the air, how far they can travel, and whether the size of the drop determines their survivability.
“The actual situation can be complicated by wind, turbulence, air recirculation or many other effects,” said Chaudhuri.
The results showed that even without a light breeze, infected drops could travel well beyond six feet.
In fact, with no wind, the droplets travel anywhere from eight feet to 13 feet before evaporating.
In addition, the longest-lived drops were between 18 and 50 microns, not even the diameter of a human hair, suggesting that masks help stop the spread.
The team says the findings could help schools and offices prepare when considering reopening measures.
“This model does not claim to predict the exact distribution of COVID-19,” said study co-author Dr. Saptarshi Basu, a professor in the mechanical engineering department at the Indian Institute of Science.
“But our work shows that evaporation or drying time of droplets is very sensitive to the ambient temperature and relative humidity.”
Ambient temperature is the air temperature of a place where equipment is stored, and relative humidity is the amount of moisture in the air compared to the air, how much the air can normally ‘hold’ at that temperature.
Researchers found that drops evaporated when the laboratory conditions were 30 ° C (86 ° F) and about 50 percent relative humidity.