Development of an animatronic headform test method for determining the efficacy of medical masks and barrier face coverings—part 2: validation study

There is a need for a realistic method to evaluate the performance of barrier face coverings and medical masks in the wake of growing respiratory concerns among the general public. In this study, the previous animatronic headform test method was optimized to evaluate the total filtration efficacy and breathing resistance of 12 products during a 10-minute simulated fit test. These products included three respiratory devices, three medical masks, and six barrier face covering styles. The revised method was able to differentiate between products with total filtration efficacies ranging from 14% to 93%, down to a difference in means of 2% at 0.3 μm optical diameter. The impact of fit was illustrated by the increase in total filtration efficacy and breathing resistance across all three medical masks when the ear loops were tightened. The coefficient of variation for each product fell below 20% at 0.3 μm optical diameter, indicating good measurement stability. A second operator conducted an intra-lab validation to determine the method's reliability. This analysis confirmed the improved repeatability and reproducibility of the headform test method, which was shown to effectively evaluate the total filtration efficacy of respiratory products as a system in a controlled laboratory setting. However, more research is needed to improve the sensitivity of the breathing resistance measurements. Comparison to the ASTM F3502-21 Standard Specification for Barrier Face Coverings highlighted the differences between evaluating these products as a sealed system or as they are intended to be worn, with an overall decrease in total filtration efficiency and breathing resistance due to leakage when evaluated on the headform.