Evaluation of Facial Protection Against Close-Contact Droplet Transmission

BackgroundFace 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. MethodsA 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. ResultsAll 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. ConclusionsThis 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 users exhalation prompts concerns for contact transmission via surfaces in exhalation flow path (e.g., face, eyeglasses, etc.).