Background: In the wake of the SARS-CoV-2 pandemic and unprecedented global demand, clinicians are struggling to source adequate access to personal protective equipment. Respirators can be in short supply, though are necessary to protect workers from SARS-CoV-2 exposure. Rapid decontamination and reuse of respirators may provide relief for the strained procurement situation. Method: In this study, we investigated the suitability of 70 C dry heat and microwavegenerated steam (MGS) for reprocessing of FFP2/N95-type respirators, and Type-II surgical face masks. Staphylococcus aureus was used as a surrogate as it is less susceptible than enveloped viruses to chemical and physical processes. Results: We observed >4 log 10 reductions in the viability of dry S. aureus treated by dry heat for 90 min at 70 C and >6 log 10 reductions by MGS for 90 s. After 3 reprocessing cycles, neither process was found to negatively impact the bacterial or NaCl filtration efficiency of the respirators that were tested. However, MGS was incompatible with Type-II surgical masks tested, as we confirmed that bacterial filtration capacity was completely lost following reprocessing. MGS was observed to be incompatible with some respirator types due to arcing observed around some types of metal nose clips and by loss of adhesion of clips to the mask. Conclusion: Considering the advantages and disadvantages of each approach, we propose a reprocessing personal protective equipment/face mask workflow for use in medical areas.

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Aircraft gas turbine engines produce ultrafine PM which has been linked to local-air-quality and environmental concerns. Regulatory sampling and measurement standards were recently introduced by ICAO to mitigate these emission of non-volatile PM (nvPM). Currently, reported nvPM emissions can significantly under-represent engine exit concentrations due to particle loss.A System-Loss-Tool (SLT) has been proposed to correct for particle loss in the standard sampling and measurement system permitting an estimation of engine exit concentrations for airport environment inventories.Thermophoretic and bend particle loss mechanisms are predicted in the SLT using expressions derived from the literature, which are not in all cases empirically validated to conditions representative of aircraft nvPM exhaust sampling methodologies. In this study, thermophoretic (Tgas≤910°C) and coiling-induced (≤3960°) particle loss were measured using sampling variables relevant to aerospace certification. Experiments were performed using laboratory generated solid particles (fractal graphite, cubical salt and spherical silica) bounding the upper and lower limits of aircraft soot morphology (i.e. particle effective density, mass-mobility exponent, primaryparticle-size). These were aerodynamically classified using a Cambustion Aerodynamic-Aerosol-Classifier (AAC) at electrical-mobility diameters ranging from 30-140 nm.The AAC was shown to efficiently classify salt and silica particles, producing monomodal distributions ≥25 nm electrical-mobility GMD, whilst classifying fractal graphite >40 nm electrical-mobility GMD (calculated as da≥20 nm) albeit generally displaying larger GSD's.Thermophoretic loss at ΔTgas of 0-880 K correlated well with the SLT for non-fractal particles with losses ≤39.2% measured, with higher depositions observed for graphite (4.1%) considered insignificant compared to overall measurement uncertainty. Coiling a 25 m sample line in compliance with ICAO standards induced negligible additional particle loss at flowrates relevant of aircraft exhaust sampling, in agreement with SLT-predicted bend losses. However, additional losses were witnessed at lower flowrates (≤13% at 30 nm), attributed to secondary flow diffusion loss induced by the coiling.

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