With continuous coughing, droplets can accumulate in the tissue and escape, reaching up to one meter away. Without the mask, the range doubles. The mask should be changed every two hours.
The use of a face mask is essential to prevent the spread and infection with the new coronavirus. However, according to a study by the University of Nicosia in Cyprus, coughing a lot when using it can end up wearing out the material, making it less efficient. The article was published on Tuesday (16) in the journal Physics of Fluids.
The researchers used computers to map the expected flow patterns of small droplets released when a person coughs repeatedly while wearing a mask. As was found in previous research, when a person coughs, droplets of saliva can travel more than five meters in five seconds – and the study took this into account when evaluating the effect of multiple coughing cycles on the mask.
The mathematical model used in the study was created using complex equations for turbulence and other flow effects. The researchers performed numerical simulations that explain the interactions of the droplets with the porous filter in a surgical mask.
Despite showing, once again, that masks reduce the spread of droplets in the air, the researchers found that the efficiency of their filters is hindered by constant coughing, as can happen when a person is sick.
With repeated coughing, some droplets can accumulate and pass through the mask, up to a meter away. Without the mask, the droplets reach two meters – showing that the use of this equipment is essential and that it is recommended to change it every two hours or earlier, when it is dirty.
Still, masks do not provide complete protection against the new coronavirus. “Social distancing remains essential,” said Dimitris Drikakis, executive director of the Research and Innovation area at the University of Nicosia and co-author of the study, in a statement.
Among health professionals, the use of much more complex personal protective equipment is required, including helmets with built-in air filters, disposable gowns, face shields, and double sets of gloves.