Researchers from Duke University assessed whether N95 respirators could be decontaminated using hydrogen peroxide vapor.
Study design
The method tested in this paper involves specialized equipment to vaporize hydrogen peroxide, which permeates all layers of the N95 to kill pathogens, including viruses, without degrading the N95 material or integrity. This hydrogen peroxide method was first utilized during the Ebola virus outbreak in 2015 to decontaminate patient rooms and ambulances. At that time no research data was available on decontaminating PPE.
An FDA-funded project previously validated the decontamination of N95 respirators with the Bioquell Hydrogen Peroxide Vapor device for over 50 cycles with the reuse limiting factor being the elastic straps that started to show degradation. The authors tested if this method could eliminate pathogens while maintaining function and proper respirator fit in health care providers.
Outcomes
The integrity and elastic of the N95 respirators were maintained for 30 cycles. The limiting step was the aeration of the N95, which was more than half of the time needed to decontaminate but can be accelerated with air evacuation systems. While waiting hours for the respirators to aerate, the biological agent can be tested to verify decontamination.
The study increased confidence among health care providers on the decontamination process because the quality assurance step did not allow the N95s to be released until the hydrogen peroxide was less than 0.1 ppm (10 times below acceptable OSHA levels), and the biological agent proved to not grow in culture. As a bonus, the process leaves no residue because the hydrogen peroxide is converted to water and oxygen during the aeration process. This method of this protocol is accessible to healthcare entities who can then choose this as a means to reuse their N95s.
Limitations
The study did not use SARS-CoV-2 as the biological agent, but the agent used here is more resistant to sterilization than the enveloped virus that causes COVID-19. Only 1 type and model of respirator was used in the study. The respirators were limited by the degradation of the elastic on the respirators to 30 cycles in prior studies, and the study did not test whether the respirators could tolerate 50 cycles.
Droplet and aerosol tests were not performed in this study, but prior studies have already validated that the integrity of the N95s is maintained after 50 cycles with droplet and aerosol testing. The study did not compare other decontamination methods such as ethylene oxide, ultraviolet light, Gamma radiation, hydrogen peroxide plasma, E-beam irradiation and alcohol soaking. However, these methods are either toxic or degrade the integrity of the N95s thus causing it to fail filtration tests.
Clinical significance
This study makes 4 valid points:
- The protocol is effective at the target organism.
- The hydrogen peroxide protocol in this study does not damage the N95 respirator.
- This decontamination method does not affect the respirator's fit.
- The process does not expose the user to toxic residue.
These 4 points yielded a high degree of confidence in its users. The published study clearly helps entities by sharing its methods and protocols. Many facilities can implement this protocol because the main items needed are a device that can produce hydrogen peroxide, a hydrogen peroxide sensor, a dedicated room and staff to perform the process of decontamination and quality assurance. This facility is admirable because they did not downgrade safety of health care providers because of supply chain problems. As a result, health care providers can perform their jobs with confidence.