A research team from the Mass General Brigham COVID Innovation Center has published a preprint study on medRxiv detailing the process they used to validate a vaporized H2O2 (VHP) system for the emergency decontamination and reuse of N95 respirators.

The team, which was led by Ebru Oral, PhD, and Orhun Muratoglu, PhD, from the Harris Orthopaedics Laboratory at Massachusetts General Hospital, in collaboration with a team led by Anthony Griffiths, PhD, at Boston University’s NEIDL, found that treating respirators with one standard cycle of VHP sterilization (Steris LTS‐V) was feasible in terms of providing effective decontamination of the SARS-COV-2 virus while preserving the fit and filter efficiency of the respirators.

A VHP system provided by the Battelle Memorial Institute and several low temperature sterilization systems by Steris have obtained an Emergency Use Authorization for this application. These systems are approved for use for 20 and 10 decontamination cycles, respectively.

Partners HealthCare is now hosting a Battelle CCDS Critical Care Decontamination System in Somerville capable of decontaminating up to 80,000 N95 masks for reuse each day.

Details of the validation process—including the specific scientific parameters used to confirm decontamination, fit and filter integrity—can be found in the preprint study.

To learn more about the team and their efforts to identify and validate new strategies for safely reusing personal protective equipment (PPE), please read the Q&A with the study team below.

Q: What was the process you used to identify and validate techniques for decontaminating N95 masks? What were the key considerations?

A: We explored mainly well-established decontamination technologies used in the hospital setting to sterilize medical devices, keeping in mind that any successful process needed to preserve the fit and filtration efficiency of a new respirator and show a significant reduction in bioburden with minimal chemical residue.  Keep the following in mind:

  • Fit is how a respirator’s shape conforms to a user’s face and creates a seal so that no air/particulates can enter the user’s nose or mouth without going through the respirator
  • Filtration efficiency is a measure of the respirator’s ability to filter out particles; an N95 mask must filter out greater than 95% of all particles larger than 0.3 µm
  • Bioburden reduction is a measure of how much the decontamination technique kills pathogens, particularly the SAR-CoV-2 virus. Since aerosolized hydrogen-peroxide is a widely used decontamination method, we know that it kills pathogens that are much more robust than the SAR-CoV-2 virus. Strips of bacterial spores (the most resistant microorganisms) are included in each run with the technique to validate the highest level of decontamination
  • Residue analysis ensures that there is no significant amount of hydrogen peroxide left on the mask that could be harmful for users to inhale on any subsequent re-wears of the mask

Finally, we also considered the number of respirators per day that needed to be decontaminated and how the logistics of the process would work within the hospital’s existing supply chain. 

The vaporized hydrogen peroxide process fit all four of these safety criteria and is a high-throughput process that can handle large numbers of respirators.

Q: Why was it important to validate in-house any proposed technique for decontaminating masks, regardless of who developed it?

A: Under normal conditions, N95 respirators are single use items not meant to be decontaminated for reuse. In this emergency, hospitals have had to repurpose existing decontamination technologies for N95 reuse. 

Since our primary goal was to ensure the safety of our health care workers, it was imperative to verify that the decontaminated respirators met the same FDA-specifications as a new respirator.

To do this, we needed to validate our in-house decontamination process. We tested the decontaminated respirators to confirm that each of the safety criteria were passed. If a method failed a validation test, it was dropped from consideration.

The expertise that we gained from conducting our own research allowed us to move quickly and decisively when commercial opportunities like the Battelle system were presented to us. Since we had done our due diligence, we were confident in the science behind the process itself and were able to act quickly in securing the dispatch of a Battelle system to Boston.

Q: What is the message to other hospitals and health care systems across the globe that are looking for ways to safely disinfect PPE for reuse?

A: The Mass General Brigham team is working with a dedicated consortium of researchers and clinician to solve the N95 decontamination problem. The results of our collaborative discussions are found on www.n95decon.org.  The website discusses a number of effective decontamination methods, so a hospital or health care system can evaluate each method to determine what will work best for their system based on available equipment and infrastructure. 

Unless a commercially validated system is chosen, hospitals should validate their choice of in-house decontamination methods for filtration efficiency, fit test, bio-burden reduction and any potential harmful residue.

Q: What is the message to health care workers in New England who are worried about the shortage of adequate PPE such as N95 masks?

A: The Mass General Brigham team’s singular focus is to find a workable, effective solution that addresses the shortage of N95 respirators for healthcare workers at Mass General Brigham hospitals, greater Boston-area hospitals and all of New England. The team is composed of dedicated researchers who are concerned about the safety of health care workers and patients.

We have been assisted by a virtual working group, a collection of over 150 amazing scientists, engineers and clinicians who are located not just in Boston but over the entire United States and even some in Europe. The group has been meeting daily to exchange information and share new results collaboratively. 

Many researchers are asking the same questions and are doing similar validation experiments.  When we put these results together, there is overwhelming evidence that some technologies—like vaporized hydrogen peroxide—work well and others—like soaking a respirator in ethanol—don’t work at all.

The common conclusions provide confidence that the decontamination methods are safe and effective because they are backed by the corroborating findings of large numbers of scientists.

Q: What are the next steps for your team?

A: Primarily, our team is continuing to monitor the vapor hydrogen peroxide disinfection efforts closely to make sure they continue to function as expected. We are also finishing up some analyses on alternate techniques, such as moist and dry heat and UVC methods to understand feasibility for hospital systems with different needs and resources.

We are hoping to assist with implementation in other hospitals in and outside the country where shortage of N95 masks could put health care workers at risk.