Development of an animatronic headform test method for determining the efficacy of medical masks and barrier face coverings—part 1: total filtration efficacy

The effectiveness of face coverings against respiratory viruses is crucial for public health but often lacks realistic performance assessments of protection and comfort. In this study, a system-level test method was developed using an animatronic headform to incorporate fit and dynamic wear into the assessment of total filtration efficacy of medical masks and barrier face coverings. Six commercially available products were evaluated, including an N95 respirator as the control. Total filtration efficacy was calculated from differential particle counts recorded inside and outside of face coverings each minute. The baseline method was able to statistically differentiate between products to a difference in means of 5% at a particle size of 0.3 μm optical diameter. The 16 and 28 L/min sinusoidal flow rates significantly impacted total filtration efficacy, as did the influence of headform movement and duration of wear for select products. There were statistical differences between operators at both flow rates for the KN95 and surgical style masks that were difficult to don consistently, highlighting the variability in performance due to fit. However, the product type remained the most significant cause of variance in the method at 66.10%, demonstrating that the headform test method was able to repeatedly and reproducibly evaluate the efficacy of various face coverings. Furthermore, there were significant decreases in filtration when the facepiece was not sealed properly due to poor fit. This highlights the importance of evaluating these source control devices, including barrier face coverings and public use of medical masks, as they are intended to be worn to incorporate their fit into the reported results.