Decontamination of N95 Respirators With Vaporized Hydrogen Peroxide Effective, Study Finds

For decontaminated respirators, researchers assessed fit on human subjects and examined filtration efficiency.

N95 respirators can be safely and effectively decontaminated with vaporized hydrogen peroxide (VHP) over 25 reprocessing cycles, a new research article says.

In the early months of the coronavirus pandemic, N95 respirators were in short supply, which created a safety concern, particularly for healthcare workers. Decontamination is one strategy to address shortages of N95 masks.

The new research article, which was published by American Journal of Infection Control, is based on data collected at a large tertiary care academic center in Boston from June 15 to Aug. 31, 2020.

Over the course of the study, the researchers tested a total of 35 3M^TM brand N95 respirators for fit and seal. From the 35, seven of the N95 respirators were tested for filtration efficiency.

There are several aspects in the methods of the research.

• The primary goal of the study was to determine whether the function and effectiveness of decontaminated N95 respirators was comparable to unprocessed respirators. "Function was defined as continued filtration efficiency greater than or equal to 95% of airborne particles of 0.3-micron or greater diameter. Effectiveness was defined as passing user seal check after every reprocessing cycle and retention of both qualitative and quantitative fit," the study's co-authors wrote.
   
• Male and female human subjects were used for fit testing rather than mannequins.
   
• A Bioquell BQ-50 hydrogen peroxide vapor generator was used to conduct the VHP decontamination.
   
• If a respirator was visibly soiled, it was removed from the study.
   
• To ventilate the respirators and the processing room, fans were used to push natural air through the room and open windows.

The testing generated two key data points.

• All decontaminated N95 respirators met benchmarks for function and effectiveness. The decontaminated N95 respirators passed 25 user seal checks as well as eight quantitative and four qualitative fit tests.
   
• Decontaminated N95 respirators achieved filtration efficiencies of at least 95%.

"VHP reprocessing appears to be a safe, viable means to augment N95 respirator supply in future epidemics. However, successfully implementing large-scale reprocessing requires multidisciplinary teams to ensure disinfection efficacy and end-user safety, as well as significant logistical support," the study's co-authors wrote.

Additional insights

N95 respirators decontaminated with VHP are comparable to unprocessed respirators, the lead author of the study told HealthLeaders.

"Based on the findings of our study, the specific brand of N95 respirators we looked at had equivalent filtration efficiency, fit, and seal to that of new N95 respirators even after 25 cycles of VHP reprocessing. To evaluate for significant degradation, we conducted a visual inspection of the N95 respirators for physical wear and tear after each decontamination cycle before participants donned them. If we saw anything suspicious, we were to dispose them per protocol. Reassuringly, we never had to dispose any of the N95 respirators we tested," said Christina Yen, MD, an infectious disease attending physician at UT Southwestern Medical Center in Dallas and associate director of antimicrobial stewardship at Clements University Hospital in Dallas.

Although the decontamination period lasts only 40 to 45 minutes, the overall process can take more than two hours, Yen said.

"This is because there are other important steps involved to ensure efficacy and safety. First, the vaporization of liquid hydrogen peroxide; second, the settling of gaseous hydrogen peroxide onto the N95 respirators; and finally, an aeration phase to ensure that all and any residual hydrogen peroxide gas breaks down into water vapor and oxygen. The final phase prevents the gas from lingering on the masks, which can cause skin irritation to the wearer," she said.

In assessing N95 decontamination, using human subjects is superior to using mannequins, Yen said. "Participants have a range of facial structures unlike mannequins. People also have differences in their baseline N95 respirator fit. Our team felt it was important to consider these real-world variations when conducting this study and assess whether they would impact fit and seal."

There are three primary elements of a conversation with healthcare workers about the safety and effectiveness of N95 respirator VHP decontamination, she said.

"First, organizational leadership's support of the use of VHP decontamination ensures that the technology has been vetted by multiple stakeholders and experts; this helps ensure safety and accountability when implementing this technology. Second, clear, routine messaging within the organization lets healthcare workers know that, while VHP decontamination of N95 respirators is still an area of active research, safety and efficacy are being prioritized and that usage of this technology is based on the latest, high-quality evidence with their wellbeing in mind. Finally, healthcare workers need to feel empowered to share their concerns about the technology and safety. Otherwise, organizations will not know what type of education, information, or gaps of knowledge are present among their healthcare workers," Yen said.

Photo Credit: Mochamad Faizal Adam