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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The project SAMPLE evaluated methods for measuring particle properties in the exhaust of aircraft engines with respect to the development of standardized operation procedures for particulate matter measurement in aviation industry. Filter-based off-line mass methods included gravimetry and chemical analysis of carbonaceous species by combustion methods. Online mass methods were based on light absorption measurement or used size distribution measurements obtained from an electrical mobility analyzer approach. Number concentrations were determined using different condensation particle counters (CPC). Total mass from filter-based methods balanced gravimetric mass within 8% error. Carbonaceous matter accounted for 70% of gravimetric mass while the remaining 30% were attributed to hydrated sulfate and noncarbonaceous organic matter fractions. Online methods were closely correlated over the entire range of emission levels studied in the tests. Elemental carbon from combustion methods and black carbon from optical methods deviated by maximum 5% with respect to mass for low to medium emission levels, whereas for high emission levels a systematic deviation between online methods and filter based methods was found which is attributed to sampling effects. CPC based instruments proved highly reproducible for number concentration measurements with a maximum interinstrument standard deviation of 7.5%.

A centrifugal particle mass analyzer and a modified differential mobility spectrometer were used to measure the mass and mobility of particulate matter emitted by CFM56-5B4/2P, CFM56-7B26/3, and PW4000-100 gas turbine engine sources. The mass-mobility exponent of the particulate matter from the CFM56-5B4/2P engine ranged from 2.68 to 2.82, whereas the effective particle densities varied from 600 to 1250 kg∕m 3 , depending on the static engine thrust and sampling methodology used. The effective particle densities from the CFM56-7B26/3 and PW4000-100 engines also fell within this range. The sample was conditioned with or without a catalytic stripper and with or without dilution, which caused the effective density to change, indicating the presence of condensed semivolatile material on the particles. Variability of the determined effective densities across different engine thrusts, based on the scattering about the line of best fit, was lowest for the diluted samples and highest for the undiluted sample without a catalytic stripper. This variability indicates that the relative amount of semivolatile material produced was engine thrust dependent. It was found that the nonvolatile particulate matter, effective particle density (in kilograms per cubic meter) of the CFM56-5B4/2P engine at relative thrusts below 30% could be approximated using the particle mobility diameter (d me in meters) with 11.92d 2.76−3 me . Nomenclature C = mass-mobility scaling component D m = mass-mobility exponent d me = particle mobility diameter k = mass-mobility prefactor M = suspended particle mass concentration m = particle mass n = particle number concentration