key: cord-0736839-jzeuwax1 authors: Rohit, Anusha; Rajasekaran, Shankar; Shenoy, Suchitra; Rai, Sumit; I, Karunasagar; Kumar D, Suresh title: Reprocessing of N95 masks: our experience from a resource limited setting in India date: 2020-12-29 journal: Int J Infect Dis DOI: 10.1016/j.ijid.2020.12.070 sha: d65b65d2d01010ea736f2be9f1e895d767bcb57c doc_id: 736839 cord_uid: jzeuwax1 OBJECTIVES: Due to the surge in the demand for N95 masks during the current pandemic of Covid-19, and considering the situation in countries grappling with acute shortages in N95 masks, we investigated the possibilities of decontamination and reuse. METHODS: Three N95 masks of different makes (A, B and C), were subjected to 6 decontamination methods, namely UV irradiation, Isopropyl alcohol (IPA) dip, Plasma sterilization ( Sterrad®), Ethylene Oxide (ETO, 3M®), Dry heat sterilization and Moist heat sterilization. The integrity of the N95 masks were assessed by measuring their particle filtering efficiency at particle size range between 0.3 and 0.5 microns. RESULTS: All the masks decontaminated with ETO and plasma sterilization retained over 95% particle filtering efficiency. Masks decontaminated using IPA dip and Autoclaving showed a drop and UV irradiation, showed variations in particle size efficiency degradation, post decontamination. CONCLUSIONS: We recommend plasma sterilization for decontamination of N95 masks in low resource settings. ETO was not recommended due to hazards associated with handling of ethylene oxide, though the filtering efficiency was retained. Since the UV irradiation method showed variations in our results, we recommend that evaluation of UV decontamination for N95 masks needs to be done on a case-to-case basis. COVID-19 has been an unanticipated pandemic of unprecedented magnitude, which has highlighted pitfalls in logistics and supply chain management of PPE and N95 masks early in the outbreak in many countries and institutions. WHO has brought out guidelines for rational use of PPE which indicates that healthcare workers exposed to aerosol generating procedures while handling COVID infected persons need to use respirator N95 or FFP2 masks or equivalent (WHO, 2020). The need for mask usage by the general population was added only recently by CDC but it has been quite clear early in the course of pandemic (CDC, 2020; Heinzerling et al., 2020) that N95 masks are required during aerosol generating procedures, splashes and sprays in the Intensive Care Units (ICUs) and Emergency Rooms (ERs). Early in the pandemic most hospitals in India were not prepared for the surge in demand for N95 masks. This was probably the case in several low and middle income countries (LMIC). Most suppliers also had diverted all masks to China as there was an exponential increase of cases in Wuhan, in February and India still had only a handful of cases involving those who had travelled back from China, Middle East or Europe. Ideally, N95 respirators and FFP2 masks are intended for single use. But due to the short supply of PPEs, we decided to start looking for alternatives to extend the use and reuse of N95 masks. No guidelines were present in early March on extended use and there were anecdotal methodologies from Nebraska Medicine (2020) and Duke's University (Schwartz et al., 2020) on reprocessing of masks. Extended use was defined as continuous use of the N95 mask when attending to more than one patient in a ward for more than one shift. Re-use of mask was defined as reprocessing the mask by various techniques recommended (sterilization or high level disinfection) and extended use following reprocessing. We decided to study the decontamination of masks using six methods that have been suggested by CDC for decontamination and reuse of filtering facepiece respirators (FFP) before formulating the SOP for extended use and reuse. Six N95 masks each from three different makes/ model numbers (A, B and C) were subjected to six decontamination methods that included UV radiation exposure, Isopropyl alcohol dip, Ethylene oxide, Autoclave, Plasma sterilization and Dry heat sterilization. The processing details are as in Table 1 . All experimental runs were in triplicate. The particle filtering efficiency of the mask for particles in the size range of 0.3 to 0.5 microns was measured before and after the mask decontamination procedure to study for any degradation in the filtering efficiency. Each mask was folded and clipped around its periphery and made into a chamber (like a bulb) leaving a small opening for the entry of the sampling tube of the "Particle concentration measuring instrument. A "METONE" air borne particle counter with a measuring range between 0.3 to 10 microns and flow rate of 28.3 litres per minute (1 cfm) was used for particle concentration measurement. This is a particle counter that is used for particle concentration measurements used for clean room classification in accordance to ISO 14644 standard. An airtight seal was provided around the sample suction tube to avoid ambient air from bypassing the mask and getting into the particle counter. The inbuilt vacuum pump of the particle counter was used to draw air through the mask (from the ambient). The flow rate through the mask was 28.3 litres per minute (1 cfm). The sampling time for each reading was 1 minute. A one minute flushing (purge) time was allowed to obtain stable and correct readings. The ambient air particle concentration in the test lab environment was considered the Upstream (USC) concentration value, which was the average of three individual readings. The particle concentration inside the mask was considered as the Downstream The degradation in the particle filtering efficiency of the mask post the decontamination process was studied by measuring the particle filtering efficiency before decontamination (Ebd) and the particle filtering efficiency after decontamination (Ead) and calculating the degradation percentage. Percentage filtering efficiency degradation of the mask is calculated as Dfe = [{(Ebd -Ead) / Ebd}*100]. All results were statistically analyzed to calculate the process mean and process Standard Deviation (SD). All methodologies were run with the respective quality controls. Filtering efficiency of the masks were studied for particle challenge falling between the size range 0.3 to 0.5 microns. Results are presented in Table 2 . Physical deformity was noticed in many of the face masks subjected to the dry heat sterilization procedure and hence the results are not provided in full. Irradiation by UV showed a wide variation in the results (81.71% for mask A, 91.11 for mask B and 95.92% for mask C), which could be due a wide variety of factors attributed to the individual makes / models. The process standard deviation ( Table 2 ) was highest for UV treatment (8.07) followed by IPA dip (2.62), autoclaving (2.23). Lowest standard deviation was with ETO treatment (0.44) and plasma sterilization was J o u r n a l P r e -p r o o f close to this (0.67). We recommend that evaluation of UV as an irradiation method for N95 masks needs to be done on a case-to-case basis. The IPA dip and Autoclaving methods showed a significant decrease in the Particle filtering efficiency post the decontamination procedure and hence we do not recommend these methods as suitable for decontamination of N95 masks. Though the filtering efficiency of N95 mask after ethylene oxide treatment was the highest, with lowest degradation, there are concerns about its use due to risks for staff and handlers. Hence the method was not considered further. N95 masks subjected to Plasma sterilization yielded filtering efficiency of 96.20% for Mask A, 94.91% for Mask B and 96.35% for Mask C (Table 2) , with second lowest degradation in comparison to the other decontamination methods. Hence, this was considered a good option for developing a protocol for N95 mask reuse. Based on the results, a protocol for extended use and re-use was created and circulated. Each user was given an N95 mask along with plasma sterilizer cover. Each user was given instructions for extended use and reuse. Extended use referred to wearing the same N95 mask for repeated encounters with patients without removing the PPE in between encounters for up to 5 days. Each person has to wear right fitting masks as FIT test is not performed before going into patient care area. The user was advised to never touch the front of the mask. Extended use of the mask was not recommended following an aerosol generating procedure in a known Covid-19 positive patient. The mask was to be removed after hand washing by holding ear loops. The front of the mask is presumed to be contaminated so the user was advised to remove slowly and carefully. We aimed to look at the best method to extend the use and attempt to decontaminate and reuse N95 masks to deal with the sudden increase in the demand for masks. All methods were based on previous experience with these techniques in the past. The importance was the safety of the user in terms of the protection offered by the mask. Though the impact of the pandemic has been relatively delayed in India with fewer deaths, prudent use of medical supplies is an urgent need considering the behavior of the pandemic so far of overwhelming the healthcare facilities as has been seen in Europe & US with exponential increase in cases. The stigma associated with the disease has also seen a steep increase in the demand for PPE such as N95 masks. According to Kobayashi et al (2020), a detailed review of policies from 27 countries on the extended use and reuse of N95 masks showed that 5 countries allowed extended use, which included Canada, France, Mexico, New Zealand and Sweden and 2 countries allowed reuse of masks, which included Germany and Netherlands. Three countries allowed both reuse and extended use and included Brazil, European region and the United States of America. The recommended methods included dry heat at 65-70°C, exposure to hydrogen peroxide vapours, Ultra violet light irradiation and moist heat. However, our study showed that the integrity of the filters was best maintained by ETO, and plasma sterilization (using H2O2 vapors). The exposure to heat in the hot air oven, as per our testing was probably for too long at a very high temperature, which destroyed the integrity of the mask, immaterial of the make and model. Extended use according to our policy ranged from 12 hours to 40 hours depending on the usage. Schwartz et al (2020) showed that exposure to vapours of hydrogen peroxide was a proven method of decontamination for reuse of N95 masks and called for an increased need to improvise and adapt given the situation of a global pandemic. They also called for each facility validating its own technique when they used Bioquell Z-2 and Bioquell ProteQ systems and hence we had to devise, improvise and formulate our policies given the current situation. Autoclaving the masks did not perform well with all the three makes/ models used in our experiment, unlike the studies from Netherlands by P.de. Man et al ( which accepted autoclaving as a simple method for decontamination of N95 masks, but it is useful to note that those experiments by P.de. Man et al were specific to a particular make and model of the mask and hence we feel those results cannot be generalized. Another study by Ma Qx et al (2020) autoclaved masks for 5 minutes and found it to be a useful technique to ensure decontamination A study by Viscusi et al (2009) which included 5 techniques of decontamination of N95 masks found the results to be make / model specific. However, their results showed that UV, H2O2 vapour exposure and ETO were most promising techniques for decontamination. They raised concerns over ETO and H2O2 vapour exposure due to throughput capabilities. But in our experiment, results of UV were make and model specific, but Plasma sterilization and ETO sterilization seemed to be stable methods across the make / models tested. To conclude, experiments to check the filtering efficiency of the N95 masks, post decontamination are necessary before formulating policies for resuse and extended use. Since the healthcare worker's safety is paramount given the large number of health care workers affected worldwide, we recommend extended use and guarded recommendation on reuse of N95 masks. Based on our experimental results, plasma sterilization was a preferred option for decontamination of N95 masks during non-availability of supplies. J o u r n a l P r e -p r o o f information/search-fda-guidance-documents/enforcemen-policy-face-masks-and-respirators-during- Standard Operating Procedure (SOP) for extended use of N95 mask for personal safety of Health Care Workers (HCW) at AIIMS Strategies for Optimizing the Supply of N95 Respirators Evaluation of five Decontamination Methods for Filtering Facepiece Respirators Enforcement Policy for Face Masks and Respirators during the Coronavirus Disease (COVID-19) Public Health Emergency Rational use of Personal Protective Equipment (PPE) for Coronavirus disease (COVID19) Sterilization of disposable face masks by means of standardized dry and steam sterilization processes; an alternative in the fight against mask shortages due to COVID-19 Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports The authors declare that they have no known competing financial interestsor personal relationships that could have appeared to influence the work reported in this paper. The authors are thankful to the Management Board of Madras Medical Mission for permission to use facilities for carrying out this work.Funding: This work did not receive funding from any source, public or private. Ethical approval: Not applicable since this is a laboratory study not involving any clinical samples or human and animal subjects.