Study: Effectiveness of Cloth Masks in COVID-19 Prevention Depends on Type of Covering

A recent study found that masks are still an effective way to prevent the spread of coronavirus disease 2019 (COVID-19), although the material of the mask can help determine the limit of the spread.

Researchers Padmanabha Prasanna Simha from the Indian Space Research Organization, and Prasanna Simha Mohan Rao from the Sri Jayadeva Institute of Cardiovascular Sciences and Research, examined the flow field of coughs under various common mouth covering scenarios.

Density and temperature are intricately related, as coughs tend to be warmer than their surrounding area, according to the study authors. Using a technique called schlieren imaging, Simha and Rao were able to visualize changes in density and capture pictures of voluntary coughs from 5 test subjects. Velocity and the spread of expelled droplets were also evaluated by tracking the motion of a cough over successive images.

The study found that N95 masks were the most effective at reducing the horizontal spread of a cough, reducing the initial velocity by up to a factor of 10 and limiting its spread to between 0.1 and 0.25 meters.

In contrast, an uncovered cough can travel up to 3 meters, but even a simple disposable mask can bring this all the way down to 0.5 meters, according to the study authors.

Using an elbow to cover up a cough was considered a “good” alternative until the researchers found that a bare arm cannot form the proper seal against the nose necessary to obstruct airflow unless covered by a sleeve. A cough is then able to leak through any openings and propagate in many directions.

In conclusion, both Simha and Rao emphasized that masks must continue to be used in conjunction with social distancing despite their findings.

“Adequate distancing is something that must not be ignored, since masks are not foolproof,” Simha said.

REFERENCE

Effectiveness of cloth masks depends on type of covering. AIP Publishing. https://publishing.aip.org/publications/latest-content/effectiveness-of-cloth-masks-depends-on-type-of-covering/. Published August 25, 2020. Accessed August 26, 2020.