Mask design, its use key for Covid control
Smaller droplets become aerosolized and remain in air for longer time
Singapore: Researchers, including one from Indian-origin, stressed that materials, design and length of face masks are important to help slow the spread of Covid-19. In the study, published in the journal Physics of Fluids, the research team looked at research on face masks and their use and summarized what we know, to date, about the way face masks filter or block the virus.
They also summarized design issues that still need to be addressed. "The results suggest that the consistent use of efficient face masks, such as surgical masks, could lead to the eradication of the pandemic if at least 70 per cent of the residents use such masks in public consistently," said author Sanjay Kumar from the National University of Singapore. "Even less efficient cloth masks could also slow the spread if worn consistently," Kumar added.
One key aspect of face mask function involves the size of fluid droplets expelled from the nose and mouth when a person talks, sings, sneezes, coughs, or even simply breathes. Larger droplets, with sizes around 5-10 microns, are the most common. These droplets are still quite small, however. To compare, a human hair is about 70 microns in diameter. Even smaller droplets, those below 5 microns, are possibly more dangerous. These can become aerosolized and remain suspended in air for long periods.
Among the many types of masks in use (cloth masks, surgical masks, and N95 masks), only N95s can filter out aerosol-sized droplets. The investigators found face masks made of hybrid polymer materials could filter particles at high efficiency while simultaneously cooling the face. The fibers used in these special masks are transparent to infrared radiation, allowing heat to escape from beneath the mask. "There could be some relation between breathing resistance and the flow resistance of the face mask which will need to be studied for a face mask-wearing interval," said author Heow Pueh Lee.