Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators

Abstract

Background: Coronavirus disease 2019 (COVID-19) has significantly impacted the health of millions of people around the world. The shortage of personal protective equipment, including N95 respirators, in hospital facilities has put frontline healthcare professionals at high risk for contracting this virus.

Aim: To develop a reproducible and safe N95 respirator reprocessing method that satisfies all presented regulatory standards and that can be directly implemented by hospitals using existing available equipment.

Methods: A non-toxic gravity steam reprocessing method has been developed for the reuse of N95 respirators consisting of 30 min of steam treatment at 121°C followed by 30 min of heat drying. Samples of model number 1860, 1860s, 1870+, and 9105 N95 respirators were either collected from hospitals (for microbiology testing) or purchased new (for functionality testing), with all functionality tests (i.e. filter efficiency, fit evaluation, and strap integrity) performed at the Centers for Disease Control and Prevention using standard procedures established by the National Institute for Occupational Safety and Health.

Findings: All tested models passed the minimum filter efficiency of 95% after three cycles of gravity steam reprocessing. The 1870+ N95 respirator model is the most promising model for reprocessing based on its efficient bacterial inactivation coupled with the maintenance of all other key functional respirator properties after multiple reprocessing steps.

Conclusions: The gravity steam method can effectively reprocess N95 respirators over at least three reprocessing cycles without negatively impacting the functionality requirements set out by regulators. Enabling the reuse of N95 respirators is a crucial tool for managing both the current pandemic and future healthcare crises.

Keywords: COVID-19; Filtration; N95 respirators; Reprocessing; Reuse; Steam.

Graphical abstract

Figure 1

Proposed gravity steam reprocessing (packaged medical devices in sealed peel pouches not containing N95 respirators are not shown). (1) Start: the sterilizer is loaded, the chamber door is sealed, and program timer is started. (2) Purge: steam flows through the chamber to displace air and preheat the load. (3) Conditioning: trapped air within the load is removed through a series of five positive pressure pulses. (4) Heat-up: the chamber/load is heated to the exposure temperature. (5) Exposure: the temperature is maintained at the exposure temperature for a set time (121°C, 30 min). (6) Exhaust: the chamber pressure is reduced to atmospheric pressure or below. (7) Drying: samples are left to dry for the selected drying time (30 min). (8) Stop: end of reprocessing process.

Figure 2

Process chart for microbiology testing on used N95 respirators.

Figure 3

Inoculation sites for the tested respirator models; 1860, 1860s, 1870, and 9105.

Figure 4

Process chart for functionality testing of used N95 respirators.

Figure 5

Filtration efficiency of three N95 respirator models before and after three full cycles of gravity steam reprocessing. ∗∗P < 0.004; ns, not significant.

Figure 6

Overall manikin fit factors for three N95 respirator models before and after three full cycles of gravity steam reprocessing. ∗∗P < 0.004; ns, not significant.

Figure 7

Strap integrity (based on tensile force exerted by the strap following a pre-stretch protocol) for the top strap and the bottom strap for three N95 respirator models before and after three full cycles of gravity steam reprocessing. ∗P = 0.027; ∗∗∗P = 0.000022; ns, not significant.