Evaluation of Facial Protection Against Close-Contact Droplet Transmission

  1. Thomas B. Stephenson
  2. Courtney Cumberland
  3. Geoff Kibble
  4. Christopher Church
  5. Sheila Nogueira-Prewitt
  6. Sebastian MacNamara
  7. Delbert A. Harnish
  8. Brian K. Heimbuch

Reviewed by

Read the full article See related articles

Listed in

Log in to save this article

Abstract

Background

Face shields are used as an alternative to facemasks, but their effectiveness in mitigating the spread of SARS-CoV-2 is unclear. The goal of this study is to compare the performance of face shields, surgical facemasks, and cloth facemasks for mitigation of droplet transmission during close contact conditions.

Methods

A novel test system was developed to simulate droplet transmission during close contact conditions using two breathing headforms (transmitter and receiver) placed 4 feet apart with one producing droplets containing a DNA marker. Sampling coupons were placed throughout the test setup and subsequently analyzed for presence of DNA marker using quantitative PCR.

Results

All PPE donned on the transmitter headform provided a significant reduction in transmission of DNA marker to the receiver headform: cloth facemask (78.5%), surgical facemask (89.4%), and face shield (96.1%). All PPE resulted in increased contamination of the eye region of the transmitter headform (9,525.4% average for facemasks and 765.8% for the face shield). Only the face shield increased contamination of the neck region (207.4%), with the cloth facemask and surgical facemask resulting in reductions of 85.9% and 90.2%, respectively.

Conclusions

This study demonstrates face shields can provide similar levels of protection against direct droplet exposure compared to surgical and cloth masks. However, all PPE tested resulted in release of particles that contaminated surfaces. Contamination caused by deflection of the user’s exhalation prompts concerns for contact transmission via surfaces in exhalation flow path (e.g., face, eyeglasses, etc.).

Article activity feed

  1. ScreenIT

    SciScore for 10.1101/2021.02.09.21251443: (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:
    All simulation studies have limitations based on the conditions and test parameters selected. Breathing patterns and droplets produced by individuals will vary dramatically from person to person in real-world settings. A manikin was used for PPE use in this study, where actual fit on humans may impact the amount of air leakage around the devices. The study was performed in a non-ventilated setting, which may have influenced transmission of particles and to a lesser degree, droplets. Samples were also taken directly in front of the transmitter headform only – additional research is needed to assess the spread of droplets at various angles. Larger sample sizes would likely improve the statistical robustness and help overcome the inherent variability of aerosol testing. An assessment of PPE on the receiver headform would also likely produce informative results for public health measures. For this study, the simulation of droplet transmission in a real-world scenario was balanced with designing a reproduceable method, enabling comparisons of various types of PPE. The focus of this study was to evaluate the effectiveness of PPE at mitigating the spread of respiratory droplets when simulating the CDC close contact condition: a minimum of 15 minutes of contact at less than 6 feet. All PPE tested were shown to be similarly effective at reducing droplet transmission up to 4 feet directly in front of the source, but were also shown to cause self-contamination. Variation in the location...

    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

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2021.02.09.21251443v1 on medRxiv