2nd June 2020

CITER researchers investigate reusing PPE

Respiratory personal protective equipment (PPE) is an essential tool for protecting healthcare workers from exposure to respiratory pathogens. These items are typically single-use and so there is a continuing worldwide demand for large volumes of PPE. In a pandemic situation, reprocessing of respiratory PPE may be a useful approach for protecting workers in the event of disrupted supply.

Following a request from Welsh Government, we assembled a team of researchers from the School of Pharmacy & Pharmaceutical Sciences and the School of Engineering at Cardiff University to address the use of potential methods for PPE reprocessing.

We investigated two potential reprocessing methods, namely dry heat or microwave- generated steam, for their microbicidal effectiveness, but also for their compatibility with two types of respiratory PPE: Type-II surgical face masks and FFP2 (N95)-type respirators.

We first examined the microbicidal efficacy of these methods against dried inocula of bacteria associated with a porous surface. We then used protocols based on the principle of the standard tests EN14683:2019 and the EN14683:2019 to determine whether the reprocessing treatment affected the capability of these masks to prevent the penetration of bacterial aerosols and the penetration sodium chloride.

We found that dry heat treatment at 70oC, (25% relative humidity) for 90 min to be effective in decontaminating both surgical face masks and respirators without compromising their bacterial and NaCl filtration efficiency, while microwave-generated steam (1800 W, 90 seconds, 100 mL in a steam steriliser) was found to rapidly inactivate bacteria. Whilst the bacterial and NaCl filtration efficiency of respirators was unaffected by this treatment method, complete loss of bacterial filtration efficiency was observed for surgical face masks. Furthermore, we showed that the specific face masks mentioned above could be reprocessed 3 times with the appropriate methods mentioned above.

Overall the use of dry heat treatment 70oC, (25% relative humidity) for 90 min is potentially appropriate for reprocessing respirators and Type-II surgical face masks. Microwave- generated steam (1800 W, 90 seconds, 100 mL in a steam steriliser) is not appropriate for the reprocessing of Type-II surgical masks.

Combining our expertise in Pharmaceutical Microbiology and Engineering, we were able to provide a rapid initial solution that can be further investigated by Welsh Government and the industry.

Pascoe MJ1, Robertson A1, Crayford A2, Durand E2, Steer J2, Castelli A1,2, Wesgate R1, Evans SL2, Porch A2, Maillard J-Y1*

1Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, Wales, UK
2School of Engineering, Cardiff University, Cardiff, Wales, UK