Researchers have found that wearing a mask no matter if it is old is not always better than not wearing anything after proving that a used surgical mask, which comes down to a leak of less than 30%, is worse than going without it, according to reports in the journal ‘Physics of Fluids’.
Although it is widely known that wearing a mask will help mitigate the community spread of COVID-19, less is known about the specific effectiveness of masks in reducing the viral load in the airways of those who wear it.
Researchers at the University of Massachusetts Lowell and Baptist University of California examined the effect of using a three-layer surgical mask on inspiratory airflows and the effects of the mask on the inhalation and deposition of environmental particles in upper respiratory tract.
“It is natural to think that wearing a mask, whether new or old, should always be better than nothing but 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, explains author Jinxiang Xi.
The researchers found that using a mask with a low filtration efficiency (less than 30%) may be worse than without it. For the development of a computational facial mask model using a physiologically realistic model of a person using a folded surgical mask and then using numerical methods to trace the particles through the mask.
They examine the behavior and fate of aerosols that pass through the mask, into the face, into the airways, and finally where they are deposited in the nose, pharynx, or lung.
The model showed that a mask changes the flow of air around the face, so that instead of air entering the mouth and nose through specific pathways, air reaches the mouth and the nose through the entire surface of the mask, but at lower speeds.
The lower speed near the face favors the inhalation of aerosols in the nose so that, although the masks filter a certain number of particles, more particles escape from the filtration of the mask that can enter the respiratory tract. .
Discover that the filtration efficiency of the three-layer surgical mask can range from 65% if it is new to 25% when used, so using a 65% mask properly will provide good protection, but using a 25% filtration mask can be worse than not using any.
“We hope that public health authorities will strengthen current preventive measures to curb the transmission of COVID-19, such as choosing a more effective mask, using it properly for maximum protection and avoiding the use of an excessively used surgical mask. or defeated, “Xi points out.
The researchers found that the folds of a surgical mask significantly affect airflow patterns, suggesting that the shape of the mask should also be considered an important factor in estimating the protective efficiency of the mask and designing new models.