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Disinfection of reusable elastomeric respirators by health care workers: A feasibility study and development of standard operating procedures

Open AccessPublished:March 25, 2015DOI:https://doi.org/10.1016/j.ajic.2015.02.009

      Highlights

      • Reusable face masks may be needed during a respiratory illness pandemic.
      • An easily deployed, reliable mask disinfection procedure is needed.
      • We developed standard operating procedures for mask disinfection.
      • Health care workers following manufacturers' instructions made multiple errors.
      • Health care workers following the standard operating procedures made no errors when disinfecting masks.

      Background

      This was a feasibility study in a Department of Veterans Affairs Medical Center to develop a standard operating procedure (SOP) to be used by health care workers to disinfect reusable elastomeric respirators under pandemic conditions. Registered and licensed practical nurses, nurse practitioners, aides, clinical technicians, and physicians took part in the study.

      Methods

      Health care worker volunteers were provided with manufacturers' cleaning and disinfection instructions and all necessary supplies. They were observed and filmed. SOPs were developed, based on these observations, and tested on naïve volunteer health care workers. Error rates using manufacturers' instructions and SOPs were compared.

      Results

      When using respirator manufacturers' cleaning and disinfection instructions, without specific training or supervision, all subjects made multiple errors. When using the SOPs developed in the study, without specific training or guidance, naïve health care workers disinfected respirators with zero errors.

      Conclusion

      Reusable facial protective equipment may be disinfected by health care workers with minimal training using SOPs.

      Key Words

      In the event of a pandemic spread by the respiratory route, a shortage of N95 respirators may be encountered. Spot shortages of N95 respirators occurred during the 2009-2010 influenza pandemic.
      • Murray M.
      • Grant J.
      • Bryce E.
      • Chilton P.
      • Forrester L.
      Facial protective equipment, personnel, and pandemics: impact of the pandemic (H1N1) 2009 virus on personnel and use of facial protective equipment.
      • Beckman S.
      • Materna B.
      • Goldmacher S.
      • Zipprich J.
      • D'Alessandro M.
      • Novak D.
      • et al.
      Evaluation of respiratory protection programs and practices in California hospitals during the 2009-2010 H1N1 influenza pandemic.
      If supplies of N95 respirators are exhausted during an epidemic, reusable elastomeric respirators may be used to protect health care workers from respiratory infection. The Veterans Health Administration (VHA) has stockpiled 3 models of reusable elastomeric respirators in several sizes to be used if a shortage of N95 respirators occurs. The Institute of Medicine, Centers for Disease Control and Prevention, and Food and Drug Administration have recently held stakeholder meetings, in part, to assess the current and potential future role of elastomeric respirators in health care settings.

      Centers for Disease Control and Prevention. NIOSH personal protective technology program healthcare stakeholder meeting. 2013. Available from: http://www.cdc.gov/niosh/npptl/resources/certpgmspt/meetings/06182013/healthcareinvitationlttr06182013.html. Accessed January 29, 2015.

      To reuse respirators safely, protocols for cleaning and disinfection after use must be developed. The procedures should be broadly applicable to the challenging conditions that may exist in a pandemic of infection spread by the respiratory route. Sterilization of respirators prior to reuse would provide the maximum level of safety, but sterilization in a central processing department poses many practical problems. Limitations imposed by temperatures which can be used on respirators and the delicacy of some of the components make steam sterilization impossible. Low-temperature sterilization methods (eg, ethylene oxide, radiation) also may damage respirator components.

      3M. Cleaning reusable respirators and powered air purifying respirator assemblies. Available from: http://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSuH8gc7nZxtUPYten8_BevUqe17zHvTSevTSeSSSSSS–&fn=RR%20and%20PAPR%20cleaning%20Ebola%20appro. Accessed November 7, 2014.

      Intermediate-level disinfection of respirators would be adequate to destroy influenza and most respiratory viral pathogens.
      • Rutala W.A.
      • Weber D.J.
      the Healthcare Infection Control Practices Advisory Committee (HIPAC)
      Guideline for disinfection and sterilization in healthcare facilities.
      One approach would be for each health care worker to take responsibility for cleaning, disinfecting, and storing their elastomeric respirator according to a standardized protocol.
      Respirators must fit the face of the individual wearer, and fit testing is required by the Occupational Safety and Health Administration (OSHA). To achieve proper fit for the broad range of facial shapes and sizes, the VHA has purchased half-face elastomeric respirators from 3 different manufacturers. Each manufacturer provides its own instructions for cleaning and disinfecting the respirator.

      3M. Cleaning reusable respirators and powered air purifying respirator assemblies. Available from: http://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSuH8gc7nZxtUPYten8_BevUqe17zHvTSevTSeSSSSSS–&fn=RR%20and%20PAPR%20cleaning%20Ebola%20appro. Accessed November 7, 2014.

      Scott. Scott Excel user's instructions. Available from: https://www.scottsafety.com/en/us/DocumentandMedia1/Engineering/UserManuals/UserManuals/595203-01_B.pdf. Accessed December 5, 2014.

      The OSHA and, more recently, the National Institute for Occupational Safety and Health (NIOSH) have also issued guidelines for cleaning and disinfecting respirators. Both agencies advise that manufacturers' instructions for cleaning and disinfecting respirators should be followed.

      United States Department of Labor, Occupational Safety & Health Administration. Respirator cleaning procedures. Available from: https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=9782&p_table=STANDARDS. Accessed January 29, 2015.

      National Institute for Occupational Safety and Health. Suggested respirator cleaning and sanitation procedures. Available from: http://www.pcocinsurance.com/2011PCOCsafetyCD/NIOSH/NIOSH_RESPIRATOR_CLEANING_SANITATION.pdf. Accessed January 29, 2015.

      The effectiveness of a dilute solution of hypochlorite (household bleach) for killing influenza on respirators has been demonstrated.
      • Subhash S.S.
      • Cavaiuolo M.
      • Radonovich Jr., L.J.
      • Eagan A.
      • Lee M.L.
      • Campbell S.
      • et al.
      Effectiveness of common healthcare disinfectants against H1N1 influenza virus on reusable elastomeric respirators.
      Bleach is also effective against a broad range of other health care–associated pathogens.
      • Rutala W.A.
      • Weber D.J.
      the Healthcare Infection Control Practices Advisory Committee (HIPAC)
      Guideline for disinfection and sterilization in healthcare facilities.
      Bleach is readily available from a number of sources, making it attractive for use in an emergency setting such as a respiratory infection pandemic or high-consequence outbreak.
      Pandemic conditions would be likely to cause personnel shortages, which may require health care facilities to use large numbers of temporary health care workers. We aimed to provide a standard method for disinfecting elastomeric respirators that could be rapidly implemented with minimal training, would be feasible under pandemic conditions, and would adhere to manufacturers' recommendations for each respirator type in the VHA cache.

      Methods

      Subjects

      The study was approved by the Colorado Multiple Institutional Review Board. Subjects provided written informed consent for participation. Subjects were registered and licensed practical nurses, nurse practitioners, aides, clinical technicians, and physicians. A total of 21 subjects were recruited. Six subjects tested manufacturers' instructions for cleaning and disinfection of a respirator and repeated the process 2 weeks later using a different respirator and the NIOSH guidelines, 6 subjects participated in development of the standard operating procedures (SOPs) for each respirator type, and 9 subjects tested the final SOPs. Subjects had no previous experience with elastomeric respirators and were blinded to the research aim to compare processes. They were informed that the purpose of the project was to develop cleaning protocols for elastomeric respirators. The six subjects who participated in development of the initial SOP, and the nine subjects who tested the final SOP were completely naive; they were not involved in any of the earlier testing.

      Respirators

      New respirators were provided from the VHA cache for the study. Tested models were 3M model 7501 (3M, Saint Paul, MN), Scott 7421 (Scott Safety, Monroe, NC), and Sperian Survivair 1050 (Honeywell Safety, Smithfield, RI).

      NIOSH's and manufacturers' instructions

      The manufacturers' and NIOSH's instructions made no mention of using personal protective equipment (PPE) to protect subjects from disinfectants when cleaning and disinfecting respirators. To protect the subjects in the study from accidental exposure to bleach when attempting to follow manufacturers' or NIOSH's instructions, a test disinfectant solution was made by mixing tap water and red dye instead of hypochlorite. This allowed for mistakes to be made and splash potential to be recorded without danger to the participants should they elect not to use PPE on their own.
      All materials needed to clean and disinfect respirators were placed in a room near a large sink, faucet, and hospital air source. Subjects were told that they would be cleaning a soiled respirator contained in a large plastic bag located on a counter near the sink. A paper copy of the applicable instructions (both the manufacturers' and NIOSH's instructions) was provided at the point of use. A container labeled chlorine bleach was pointed out, and subjects were told that red dye had been added to the bleach to check for splashes. Subjects were informed that no additional instructions would be given during the study session and no questions would be answered; however, they could ask questions or make comments or suggestions. Subjects were also informed that their voice would be recorded and video would be taken of their hands during each study session. This allowed observers reviewing the sessions to note times involved in each step, tasks completed correctly or incorrectly, and questions or comments made by the subjects.

      Development of new SOPs

      After observing a high error rate in subjects' disinfection technique when using manufacturers' and NIOSH's instructions, SOPs were developed for each respirator model. An iterative process was used to design, test, redesign, and retest SOPs. Incremental knowledge gained with each design was used to improve instructions, which were crafted to maximize ease of use and minimize errors.
      • Rubin J.
      • Chisnell D.
      Handbook of usability testing.
      • Jolly J.D.
      • Hildebrand E.A.
      • Branaghan R.J.
      Better instructions for use to improve reusable medical equipment (RME) sterility.
      • Anderson J.
      • Gosbee L.L.
      • Bessesen M.
      • Williams L.
      Using human factors engineering to improve the effectiveness of infection prevention and control.

      Cleaning and assessing head straps for loss of elasticity

      Manufacturers' instructions stated that straps should be removed prior to disinfection of the respirator. Because of concern for contamination of straps when worn by subjects caring for patients with respiratory viral infection and the need to include them in the disinfection process, we tested the effect on the straps of repeated exposure to the disinfection solution. Prior to any disinfection treatment, each strap was stretched to its maximum length, and the applied pressure was measured with a luggage scale (Travelon, Elk Grove, IL). The luggage scale was tested for reproducibility of measurements. On 20 independent replicates, the scale gave a mean weight ± SD of 13.54 ± 0.14 kg. Straps were soaked in hypochlorite disinfection solution for the prescribed time and then air dried daily for 45 days. After this, the straps were measured under application of the same amount of force applied at baseline.

      Statistical analysis

      The proportion of subjects who made errors when following manufacturers' and NIOSH's instructions was compared with those using the final SOPs. Fisher exact test was used to test significance of the differences. All tests were 2 tailed. Calculations were performed in GraphPad Prism (GraphPad Software, La Jolla, CA). P values <.05 were considered significant.

      Results

      Evaluation of manufacturers' and NIOSH's instructions

      The manufacturers' and NIOSH's instructions did not make mention of wearing PPE to prevent exposure to disinfectants when cleaning and disinfecting respirators. After each cleaning and disinfection episode, examination of all 21 subjects and their environment demonstrated test disinfectant solution on gowns, the floor, and around the sink.
      All manufacturers' instructions were printed in a small font, which made them difficult to read. In addition, the manufacturers' instructions for 3M and Scott did not specify contact time for disinfectant solutions, and both of their masks floated in the disinfection solution, compromising the process as written.
      Subjects noted that the NIOSH's instructions made no mention of PPE and did not give disinfection times.

      Process observations and development of the optimized SOPs

      To carry out the optimized procedure, a sink with space to accommodate two 2-gallon buckets was needed. Using an immersible thermometer to fill exactly 1 or 2 gallons at a specific temperature proved problematic and time-consuming because subjects would empty some of the water and fill with more hot or cold as needed. To solve this problem, the SOPs specified that subjects were not to don PPE until the buckets were filled with water only; therefore, they could judge its temperature with bare hands and then don PPE before adding detergent and bleach. Both manufacturers' and NIOSH's instructions gave a maximum temperature but not a minimum. The temperature of warm water was defined to be between 85°F and 110°F.
      The 3M and Scott respirators floated in the disinfectant solution, leaving portions of the respirator with inadequate contact time with disinfectant. This problem was solved by using tongs to turn the mask in the solution to remove air bubbles and then placing the tongs on the mask to weigh it down and keep it submerged.
      During initial studies of manufacturers' and NIOSH's instructions, vigorous scrubbing on the inside of the mask occasionally dislodged or displaced the delicate inhalation valves. To correct this problem, instructions for gentle handling were included in the SOPs. Workers found it difficult to reattach filters to the 3M and Scott respirators. The Scott mask and filters are both black, as are the small arrows to indicate placement. Minutes were lost while subjects tried to reattach filters.
      There were 11 distinct errors made during the process (Table 1). Therefore, the 6 subjects who tested the manufacturers' instructions had a total of 66 opportunities for error and committed 31 errors. When using the NIOSH's instructions they made 22 errors in 66 opportunities.
      Table 1Errors made during disinfection of elastomeric respirators
      Errors madeManufacturers' instructionsNIOSH's instructionsInitial SOP, first attemptInitial SOP, second attemptFinal SOP, first attemptFinal SOP, second attempt
      PPE not used5/6 (83%)5/6 (83%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Unable to remove filters3/6 (50%)0/6 (0%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Removed inhalation valves2/6 (33%)1/6 (17%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Poured detergent directly onto brush3/6 (50%)0/6 (0%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Poured detergent directly onto mask1/6 (17%)0/6 (0%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Poured undiluted bleach directly on mask1/6 (17%)0/6 (0%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Did not immerse mask in soapy water4/6 (67%)2/6 (33%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Did not clean filter covers or splash guards4/6 (67%)4/6 (67%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Immersed filters in soapy water or disinfectant0/6 (0%)2/6 (33%)0/6 (0%)0/6 (0%)0/9 (0%)0/9 (0%)
      Did not mix disinfection solution correctly4/6 (67%)2/6 (33%)1/6 (17%)0/6 (0%)0/9 (0%)0/9 (0%)
      Did not complete disinfection step correctly4/6 (67%)6/6 (100%)1/6 (17%)0/6 (0%)0/9 (0%)0/9 (0%)
      Did not complete all steps correctly6/6 (100%)
      Manufacturers' instructions versus final SOP (P < .002).
      6/6 (100%)
      NIOSH instructions versus final SOP (P < .002).
      2/6 (33%)0/6 (0%)0/9 (0%)0/9 (0%)
      Total errors made on first attempt/opportunities for error31/66 (47%)22/66 (33%)0/99 (0%)0/99 (0%)
      NIOSH, National Institute for Occupational Safety and Health; PPE, personal protective equipment; SOP, standard operating procedure.
      Manufacturers' instructions versus final SOP (P < .002).
      NIOSH instructions versus final SOP (P < .002).

      Performance of the final SOPs

      There were zero errors in 99 opportunities among the 9 naïve subjects who tested the final SOPs. The temperature of all cleaning and disinfecting solutions prepared by subjects using the final SOPs was between 85°F and 110°F.
      The mean time ± SD needed to complete cleaning and disinfection using the SOPs for the first time was 23 ± 3.3 minutes and 16.1 ± 2.5 minutes on the second attempt.

      Impact of disinfection process on straps

      After daily treatment with the disinfection process for 45 days, the Sperian respirator strap stretched 3.9% longer than baseline, the 3M respirator strap stretched 7.1% more than baseline, and the Scott respirator strap did not change.

      Discussion

      This study demonstrates that clear and concise SOPs for cleaning elastomeric respirators can be developed using iterative design concepts. Input from subjects who are the likely end users contributed to the final design of the SOPs. Reliance on manufacturers' instructions or NIOSH's instructions alone was associated with a large number of errors. Naïve health care workers performed error-free cleaning and disinfection of elastomeric respirators using the final SOPs that were developed.
      In the event of a respiratory viral infection pandemic, the health care system must be prepared to act quickly and effectively to protect health care workers. During the 2009 influenza pandemic, spot shortages of disposable N95 respirators were encountered, prompting the VHA to stockpile reusable elastomeric respirators in preparation for a future pandemic. Stockpiles of PPE are useful only if health care workers are prepared to use them properly. This study provides SOPs for cleaning elastomeric respirators that can be deployed in many health care settings, using supplies that are readily available from numerous sources.
      There is a growing recognition that human factors engineering can be used to improve efficiency and accuracy in health care operations. We sought to apply human factors principles to pandemic preparations. A human factors study of SOPs developed for endoscope cleaning has demonstrated improved adherence to manufacturers' guidance when SOPs were developed and implemented.
      • Jolly J.D.
      • Hildebrand E.A.
      • Branaghan R.J.
      Better instructions for use to improve reusable medical equipment (RME) sterility.
      Our results with the SOPs for elastomeric respirator cleaning and disinfection were similar, showing significantly fewer errors when following our SOPs than when using manufacturers' or NIOSH's instructions.
      SOPs may be written with a goal of good initial performance to ensure that workers perform at a high level on initial efforts. If the goal of the SOP is training and transition to independence from the SOPs, a more abstract instruction set may be used, sacrificing initial performance.
      • Eiriksdottir E.
      • Catrambone R.
      Procedural instructions, principles, and examples: how to structure instructions for procedural tasks to enhance performance, learning, and transfer.
      Our goal was to ensure highly accurate initial performance of the process under challenging conditions with minimal training. Therefore, we wrote detailed procedural instructions with pictures.
      Our study has several limitations, including the relatively small number of subjects and the single-center design. Selecting the proper volume of bleach requires attention to detail because chlorine concentrations are not standard among commercial products. Bleach purchased from hospital supply firms had hypochlorite concentrations of 5.25%-6.0%. Bleach purchased from retail stores for consumer use had a hypochlorite concentration of 8.25%. If supply shortages during a pandemic force hospitals to use consumer markets, the hypochlorite concentration of the product selected must be carefully assessed. Our initial objective was to create a single SOP that could be used for all respirator types during a pandemic spread by the respiratory route. We were unable to accomplish this because each manufacturer specified a different concentration of bleach for its respirator. Users may insert the proper volume of bleach (Table 2) into the SOPs (Fig 1). A disadvantage of bleach disinfection of respirators that has been noted by others is the residual chlorine odor. When chlorine off-gassing was quantified, it was found to be very low after air drying the respirator overnight.
      • Viscusi D.J.
      • Bergman M.S.
      • Eimer B.C.
      • Shaffer R.E.
      Evaluation of five decontamination methods for filtering facepiece respirators.
      Measurements of changes in elasticity after exposure to disinfection conditions did not include subjects wearing the respirators. Therefore, the impact of stretching the straps between exposures to bleach was not assessed. The minimal changes in elasticity that we identified could be mitigated by adjusting the straps.
      Table 2Bleach concentrations
      Final hypochlorite concentrationVolume of 5.25% bleach in 2 gallons waterVolume of 8.3% bleach in 2 gallons water
      200 ppm 0.02% hypochlorite1 oz (30 mL)20 mL
      400 ppm 0.04% hypochlorite2 oz (60 mL)40 mL
      800 ppm 0.08% hypochlorite4 oz (120 mL)80 mL
      1,250 ppm 0.125% hypochlorite6.25 oz (188 mL)126 mL
      5,000 ppm 0.5% hypochlorite 1:10 bleach/water dilution25 oz (750 mL)500 mL
      Figure thumbnail gr1a
      Fig 1Standard operating procedure. PPE, personal protective equipment; SOP, standard operating procedure.
      Figure thumbnail gr1b
      Fig 1Standard operating procedure. PPE, personal protective equipment; SOP, standard operating procedure.
      The SOPs were developed for a single health care worker to disinfect a single respirator at one time. The amount of time required for health care workers to disinfect a respirator averages 16 minutes on the second attempt. Application of these SOPs to a large number of health care workers completing their duty at the same time may result in excessive wait times for a single sink. This could be addressed by staggering shifts or by providing multiple work areas for cleaning and disinfection. Filling and mixing the solutions in buckets for each disinfection episode was the most time-consuming part of the procedure. This could be remedied with the use of laboratory water bath for cleaning and disinfection solutions. By making warm soapy water and disinfecting solutions every 8-12 hours and keeping them at a constant temperature, health care workers would be able to clean and disinfect the respirators more quickly and efficiently.
      Development of optimized SOPs solved many of the problems encountered by subjects using manufacturers' instructions. Still, some issues may require redesign of respirators. For example, subjects had difficulty reattaching filters on some brands of respirators after cleaning and disinfection. Arrows to indicate correct filter placement could be added by these manufacturers in a color which could be distinguished from the masks and filters to facilitate correct reattachment.
      New modalities, such as special washers-sterilizers, which would not damage elastomeric respirators, countertop ultraviolet light disinfections units, or even designated rooms with ultraviolet light to hang clean respirators, could be considered in the future.
      The final concentrations of bleach used in the SOPs were selected to adhere to manufacturers' recommendations, which ranged from 50-400 ppm. The concentration previously tested and shown to inactivate influenza virus was 1,000 ppm. Tests of elastomeric respirators treated with these higher concentrations of bleach have not been reported. 3M has published online guidance stating that the 5,000-ppm concentration may be used for their respirator and advising users to carefully examine the respirator for damage with each use.

      3M. Cleaning reusable respirators and powered air purifying respirator assemblies. Available from: http://multimedia.3m.com/mws/mediawebserver?mwsId=SSSSSuH8gc7nZxtUPYten8_BevUqe17zHvTSevTSeSSSSSS–&fn=RR%20and%20PAPR%20cleaning%20Ebola%20appro. Accessed November 7, 2014.

      Bleach may be used to disinfect respirators contaminated with other agents (eg, Ebola, Bacillus anthracis). However, there are numerous additional considerations that would need to be included in SOPs for safe disinfection of these pathogens, including additional PPE to protect workers from higher bleach concentrations, contact time, bleach concentration, and pH. Our final SOPs deviate from manufacturers' instructions to remove the strap before disinfection. We demonstrated that daily exposure of the straps to the cleaning and disinfection process for 45 days resulted in minimal change (<10%) in the elasticity of the straps. We believe complete disinfection of the respirator includes disinfection of the straps, and we designed the SOPs to reflect this.
      In summary, we have designed and tested SOPs for elastomeric respirators that can be rapidly deployed in the event of a large-scale airborne infectious disease outbreak.

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