Characterization of a novel, low-cost, scalable ozone gas system for sterilization of N95 respirators and other COVID-19 related use cases.

  1. Nikhil Dave
  2. Katie Sue Pascavis
  3. John Patterson
  4. Michael Kozicki
  5. David Wallace
  6. Abhik Chowdhury
  7. Morteza Abbaszadegan
  8. Absar Alum
  9. Pierre Herckes
  10. Zhaobo Zhang
  11. Josh Chang
  12. Clinton Ewell
  13. Tyler Smith
  14. Mark Naufel

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Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an elusive and highly pathogenic agent, has resulted in the ongoing COVID-19 pandemic affecting numerous populations worldwide. New studies investigating the tenacity of SARS-CoV-2 have highlighted its ability to persist on a myriad of surfaces for several days, including gowns and shoes. As a result, there is a global need for sterilization of a variety of potentially-contaminated items, ranging from clothing to personal protective equipment like face coverings. To this end, we have designed and constructed a cost-effective, scalable, and sustainable sterilization system that uses ozone gas to inactivate viral particles. We sought to determine the efficacy of the system in the sterilization of viral particles as well as its ability to sterilize N95 respirators for reuse. N95 respirators inoculated with P22 bacteriophage and sterilized in the ozone system showed a 6-log 10 reduction in viral load when treated at 25 ppm for 150 minutes. Further, N95 respirators treated with five 150-minute cycles at 35 ppm for a total concentration-time product (CT) of 26,250 ppm min in the ozone system showed comparable filtration efficiency to untreated N95 respirators in a 50 to 200 nmr particulate challenge filtration test. Interestingly, the surgical N95 respirators tested showed complete inactivation of fluid resistance and degradation of the elasticity of polyisoprene straps after five cycles in the sterilization system. Taken together, these data suggest that while our ozone system may negatively affect certain protective aspects of surgical N95 respirators, it does effectively sterilize viral particles and can be utilized for a multitude of other use cases, including sterilizing polypropylene face coverings after potential SARS-CoV-2 contamination. In addition to providing long-term environmental benefits, deployment of this system during the ongoing pandemic reduces the risk of COVID-19 community transmission while conserving monetary resources otherwise spent on the continuous purchase of disposable face coverings.

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  1. ScreenIT

    SciScore for 10.1101/2020.06.24.20139469: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Finally, the real-world limitations of ozone sterilization for personalized protective equipment (PPE) and other items must be considered. While shoes and other items demonstrated no visible degradation after sterilization (see Supporting Information), outside wear and contamination could decrease the durability of ozone-treated items. Precautions against wear of use, such as examining sterilized articles for deformation or sterilizing for less than the validated number of cycles, should be taken. Another consideration for real-world use is the potential impact of ozone gas on human health. For safety, OSHA requires ozone gas exposure to remain below .1 ppm over an 8-hour, time-weighted average [22]. We have shown that in a typical occupied space with limited ventilation, ozone concentrations 15 minutes after each treatment cycle remain much lower than maximum the OSHA permissible exposure limit (PEL), indicating the safety of the described system (see Supporting Information) [22]. Nevertheless, after a treatment cycle, one should turn their head away from the system when opening the chamber, allow the gas to disperse for 10 minutes before removing any items, and only open the system in a well-ventilated space [23].

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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  2. Version published to 10.1101/2020.06.24.20139469v1 on medRxiv