The New York Post:
Wearing a used mask could be more dangerous than not wearing one at all when it comes to warding off COVID-19, a new study has found.
A new three-layer surgical mask is 65 percent efficient in filtering particles in the air — but when used, that number drops to 25 percent, according to the study published Tuesday in the Physics of Fluids.
Researchers from the University of Massachusetts Lowell and California Baptist University say that masks slow down airflow, making people more susceptible to breathing in particles — and a dirty face mask can’t effectively filter out the tiniest of droplets.
“It is natural to think that wearing a mask, no matter new or old, should always be better than nothing,” said author Jinxiang Xi.
“Our results show that this belief is only true for particles larger than 5 micrometers, but not for fine particles smaller than 2.5 micrometers.”
To reach their findings, researchers used a computer model of a person wearing a pleated three-layer surgical mask to track how the face covering affected airflow and how particles passed through. They also looked at how the tiny droplets settled onto the face, in the airway and where they land in the nose, pharynx or deep lung.
They found that wearing a mask “significantly slows down” airflow, reducing a mask’s efficacy and making a person more susceptible to inhaling aerosols into the nose — where SARS-CoV-2 likes to lurk.
“In this study, we found that the protective efficacy of a mask for the nasal airway decreases at lower inhalation flow rates,” the study said.