Covid-19: A mask will help, but only if worn properly

New Delhi: As Covid-19 once again holds us in its vice-like grip, it’s time for a re-look at the latest scientific studies to determine the best protection against the pandemic and here I refer particularly to the face masks. Besides vaccination, social distancing, indoor ventilation, frequent and thorough hand wash, face masks are an integral part of the protection, and unlike when the pandemic first hit us, today, there is ample scientific evidence to show the importance of masks in controlling the spread of the virus.

Even more noteworthy are studies that have shown how the effectiveness of the mask is to a large extent dependent on the fit of the mask and how it is worn. Or to put it differently, even the best mask cannot give the protection that it promises, if it does not fit properly or is worn loose. Given the way most people in India wear their masks, this information really needs to be driven home.

A study titled “Comparing the fit of N-95, KN95, surgical and cloth face masks and assessing the accuracy of fit checking” and published in PLOS ONE in January 2021, for example, emphasises that a correct fit is absolutely critical to the level of protection offered by masks. After comparing various kinds of masks, the researchers observed : “While the importance of wearing face masks has been acknowledged, there remains a lack of understanding about the role of good fit in rendering protective equipment useful.”.

Another research paper published in the Physics of Fluids in 2021, amplifies this further. Since aerosols dispersed by an infected person is the source of transmission of the Covid-19 virus, engineering researchers at Waterloo University, Canada, measured , using a mannequin, the buildup of aerosol droplets exhaled from a person in a large unventilated room, using different kinds of masks. What they found was that the filtration efficiencies of masks in respect of exhaled air were much lower than the rated efficiencies because of poor fit and the resultant leakages from below the chin, around the cheeks and over the nose.

Surgical and cloth masks, with about 50 per cent rated efficiencies, for example, actually filtered only about 10-12 per cent of the exhaled aerosol droplets on account of their poor fit and the remaining aerosols got redirected mostly towards the top of the mask where it fits over the bridge of the nose and escaped, unfiltered. High efficiency masks with rated filtration efficiencies of 95 per cent on the other hand, filtered 46-60 per cent of the exhaled aerosols, again on account of gaps between the face and the mask, the study said..

The research paper, titled “Experimental Investigation of Indoor aerosol dispersion and accumulation in the context of covid-19: effects of masking and ventilation” concluded that “if worn correctly, high efficiency masks still offer significantly improved filtration efficiencies over the most commonly used surgical and cloth masks “.

Obviously, better fitted and third party certified high efficiency respirators that filter 94-95 per cent of airborne particles, offer the best protection in indoor settings with poor ventilation, but because of the cost factor, many experts recommend double masking as an alternative.

A research titled “Fitted Filtration Efficiency of double masking during the Covid -19 pandemic” , published in Jama Internal Medicine in April 2021, showed that wearing a disposable surgical mask underneath a re-usable cloth mask considerably improved the overall FFE range The experiment, using three volunteers, checked the FFE of cloth mask and a procedure mask used singly and in combinations.

The mean FFE range for a single cloth mask was 41 to 44 per cent, while that for surgical mask was 43-62 per cent. However, wearing a procedure mask under the cloth face mask produced a marked improvement in overall FFE , ranging from 66-77 per cent with cotton mask and 81 per cent with polyester gaiters. Here too, the paper emphasizes the importance of reducing leakages from the periphery of the mask when it points out that such double masking also minimized the leaks between the mask and the facial skin, including the bridge of the nose .

So remember, your mask should not only fit you well, but should be worn in such a way as to reduce to the bare minimum, the gaps between the face and the mask, particularly over the nose.