Surgical masks will not protect one from contracting the COVID-19 as they are intended to protect third parties and not the users, university Department of Electronic Systems Engineering lecturer Marc Anthony Azzopardi said.

“A surgical face mask is designed to limit the aerosols emitted from a surgeon’s mouth and nose from contaminating the surgical field. They protect the patient from the surgeon, and not the surgeon from the patient.

“The mask material has pores many times larger than a virus and is not tight-fitting to the face. Hence, they are not very effective at protecting the wearer from very fine dust, or indeed virus-laden aerosols. They are, however, somewhat effective at preventing one from touching the nose and face with possibly contaminated hands,” he said.

Azzopardi said respirators, on the other hand, were much better fitting to the face and meant to seal. They needed to be fit tested and should be used together with other personal protective equipment, particularly eyewear for maximum effectiveness.

Yet, high-performance respirators were actually “electrical devices” that worked using the physics of electrostatics to attract and then trap the tiniest of particles inside their non-woven electret polypropylene filters. 

Electret materials were dielectric materials that retained a semi-permanent electrical charge within them. As long as this electrical charge persisted inside the material making up a face respirator, very small particles (down to a few 10’s of nanometres) were reliably lodged within the mask.

This gave these respirators the 95% or higher filtration efficiency, without making it unduly difficult to breathe through. It made them suitable for handling hazardous dust and fibres, such as lead or asbestos.

Face respiratorsFace respirators

Both face masks and respirators, Azzopardi said, might become contaminated after use and must not be touched.

If touched, the hands must then be washed immediately and thoroughly. Removal and disposal also had to be performed very carefully, lest these masks and respirators became themselves a source of infection.

“In times of shortages, the temptation arises for reusing such disposable masks/respirators. Since these could have been contaminated, reuse is highly inadvisable. Research suggests that it may take many hours, possibly several days for viable virus concentrations to drop sufficiently to make used masks safe to handle or reuse.

“Moreover, washing a high-performance respirator with alcohol, water, detergent, or bleach damages these respirators irreversibly, by discharging the electret that makes them work. Autoclaving and other forms of heating also damages them. Medical practitioners in particular, should be especially careful,” he warned.

Azzopardi said that an experimental technique involving intense short-wavelength (253 nm), germicidal ultraviolet radiation (UV-C) shows promise for sterilisation with minimal mask damage, and has been researched by several groups around the world.

This is currently being evaluated at the University of Malta to mitigate the severe shortages of high-performance respirators, particularly for medical professionals.

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