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PE RSONAL PROT ECT IVE EQUIPMENT


be decontaminated in the event of a crisis. British manufacturers are now on the case and national bodies have conducted their own validation work on decontamination processes. “The big question is, are we ready for phase two? Only time will tell,” she concluded.


Practicalities of PPE reprocessing Brian Crook, from the microbiology team at HSE Science and Research Centre, went on to discuss the practicalities of PPE reprocessing and the lessons learned for the future. In response to PPE shortages, he explained that the Government had set up a Reuse Rapid Review Panel to consider possible options.


The panel concluded that the highest priority and likelihood of success was the reuse of surgical gowns and FFP3 respirators. While a separate workstream was set up for surgical gowns, Crook was part of an expert team that looked at the reuse of FFP3 respirators. They concluded that: l Autoclaving was probably too destructive; l Heat treatment was also probably too destructive;


l The best options were fumigation methods;


l Hydrogen peroxide was most promising.


Vaporised hydrogen peroxide (VHP) was considered to be well established, with known efficacy, and was already used in many hospital Trusts. FFP3 respirators could be fumigated and returned to the original user, but the process needed to be validated and it was important to ensure that fumigation did not dimmish the effectiveness of the PPE. Bioquell had already conducted research for Health Canada investigating the possible use of VHP to fumigate N95 respirators, and the Microbiology Team at the HSE Science and Research Centre had loan of a


Bioquell ProteQ VHP machine, so there was an opportunity to test fumigation of FFP3 respirators, relevant to the European market. The team decided to use similar methods to the Canadian study.


Testing of VHP Five brands of FFP3 respirators, from three different suppliers, were tested – including three valved and two unvalved types. A controlled environment test chamber was used and the ProteQ VHP machine was set up to hospital parameters and adjusted to the room configuration. The FFP3s were suspended for maximum VHP penetration, and Geobacillus stearothermophilus spores were put onto steel discs and inserted in between the layers of material of the FFP3s. This provided a biological indicator. Up to 10 of each FFP3 type was put through either 10 or 20 cycles of VHP fumigation with untreated FFP3s kept for comparison. The mean VHP delivery for all cycles was 773.5ppm (range 650- 926.9ppm). The biological indicators used in the first five cycles were then analysed


for spore survival compared to unexposed controls and colour change chemical indicators were used to cross reference the biological indicators. After each fumigation cycle, each mask was put on a ‘Sheffield Head’ manikin to mimic wear, including strap stretching. The FFP3s were visually assessed after decontamination cycle 2, 4,7, 11, 14 and 20 for any possible defects including: misshapen respirators, damaged material and obvious deterioration in strap integrity, strap attachments, valves and nose pieces. The masks were also tested for off- gassing of hydrogen peroxide using PortaSens to monitor levels straight after fumigation and after a period of aeration and storage. One set of each FFP3 type was put through filter penetration testing, using a salt aerosol challenge to look for any increased leakage through 10 and 20 cycle FFP3s, compared to untreated ones. In addition, a ‘portacount’ quantitative fit test of 10 and 20 cycle FFP3s was performed and compared to untreated ones, on volunteers.


Results


The results showed there was a >4 log kill in 46/50 of the tests (92%). There were some initial set up problems with the placement of the biological indicators for the first run, leading to shadowing and reduced kill (<4 log) in three sets of samples. Crook also pointed out that the spores used in the test were much more resilient to any decontamination method than enveloped viruses.


In terms of FFP3 damage, the tests found strap breakage for three respirators after 2, 7 and 11 cycles. The nose piece material parted from the main respirator fabric for 12 respirators, mostly after 11 cycles, although similar problems were also found with some untreated respirators.


The team did find off-gassing with hydrogen peroxide at significant levels of between 2.5 and 14.1 ppm, two hours


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