University of Malta designs hardware to disinfect face respirators

In times of severe Personal Protective Equipment (PPE) shortages, healthcare workers are faced with a vexing dilemma: they can either throw away their precious face respirators after each shift, and quickly run out of them, or they could reuse them with the considerable risk that a contaminated respirator could itself become the cause of infection.

Therefore, until the market for PPE and ventilators adjusts to the vastly increased levels of demand, Malta’s engineering community can contribute by quickly finding interim technical solutions that can mitigate the immediate risks.

The Department of Electronic Systems Engineering has designed and built prototype equipment that uses short wavelength Ultraviolet Germicidal Irradiation (UVGI) and the concomitant generation of Ozone gas, to substantially reduce the viral bioburden of up to nine disposable face respirators concurrently in a few minutes, so that they may be re-used in greater safety by medical personnel facing shortages. Once delivered, the equipment will include interlocks that will prevent accidental exposure of staff to UVGI which is associated with severe eye and skin damage.

“Engineers are no strangers to the technology behind personal protective equipment, including respirators. These have been routinely used in a variety of high-risk industries for many decades, even before the study of microbiology came into existence. We can therefore share our collective expertise and systems-design training to contribute to the national COVID-19 effort. In an emergency, we can for example, develop such safe and practical disinfection equipment that minimises the reduction in the filtration performance of disposable respirators, and there is other live-saving equipment that we are currently working on.

“The ultimate effectiveness of COVID-19 disinfection protocols for locally available respirator types is, of course, for the Infection Control Specialists to determine. However, by working together we can keep our health workers safe and well supplied with the equipment they need.”

Up until Friday, in Italy, over 50 doctors have died from COVID-19 and more than 6400 health workers have been infected. This is far higher than the national rate of infection, and could only boil down to insufficient availability PPE and/or or inadequate PPE types, and/or incorrect use and reuse of the same PPE.

“After reviewing two decades of peer-reviewed research literature on disinfection methods for disposable PPE, we selected a promising solution that appears very effective in destroying most pathogens without destroying the PPE itself in the process. Published research shows that with UVGI, a wide range of pathogens, including viruses, are very efficiently inactivated. UVGI-treated respirators could thus be reused multiple times before they start visibly deteriorating. Until that happens, they seem to retain most of their air filtration effectiveness.”

This relatively simple and low-cost equipment can be quickly built in large numbers should the need arise. Each such unit can process over 400 specialised N95/FFP2 face respirators per day, and the prototype will be donated to the Department of Infection Control at Mater Dei Hospital for evaluation in the coming days.

Respirators are specialised face masks rated to international standards like NIOSH N95 and EN149 FFP2. They are generally not designed for re-use, but the United States Food and Drug Administration (FDA) have just issued an Emergency Use Authorization (EUA) for Reprocessing of Filtering Facepiece Respirators, provided that there is evidence to “demonstrate a robust ability to reduce bioburden on the masks” and that “repeated exposure to reprocessing cycles does not interfere with the filtration ability or breathability of the masks.”

The “electret” filtration media used in such respirators is easily damaged by common disinfection methods.

“The chronic global shortage of personal protective equipment is now one of the most urgent threats to our collective ability to save lives,” WHO chief Tedros Adhanom Ghebreyesus told a virtual news conference in Geneva.

This content was supplied by Dr Ing Marc Anthony Azzopardi, Department of Electronic Systems Engineering, University of Malta