ABSTRACT
Surgical and community face masks are used worldwide to reduce the transmission of respiratory infections in indoor environments. Performance parameters for these loose-fitting devices are mainly focused on material filtering efficiency, while, differently from face respirators, there are no standard methods for measuring the fraction of air leaking at the face seal. This study quantifies the total filtration efficiency (TFE), a parameter based both on filter efficiency and air leakage, of 50 face mask models with the aim of understanding the role of several mask design features on TFE performance. An instrumented head form equipped with sensors for measuring volumetric airflow and differential pressure was used to simulate the air exhalation from the mouth of a person wearing a face mask. A response surface method (RSM) was used to model the TFE experimental data. Results showed that TFE values ranged over a wide interval (from 5% to 73%), with better values at higher flow rates. A significant positive correlation was found between TFE and filter breathability. The presence of a nosepiece (NP) showed to increase the TFE on average from 4% to 6%, according to the flow rate. Significant improvements were associated only to nosepieces incorporating a metallic wire. The RSM model evidenced that the increase in the number of the filter layers and the use of a meltblown layer result in higher TFE only when a nosepiece is in place. Differently, the benefit of the nosepiece is less marked for masks made of highly breathable filters. To improve overall mask performance, the design of loose-fitting face masks should carefully compromise between breathability and filtration efficiency of the filter materials. The addition of a metallic nosepiece helps improving the TFE by limiting the air leaking at the face seal. © 1963-2012 IEEE.
ABSTRACT
Face masks are used worldwide to reduce COVID-19 transmission in indoor environments. Differently from face respirators, there are no standards methods for measuring the fraction of air leaking at the face seal of loose-fitting masks such as medical and community masks. This study applies a recently developed method to quantify air leakage at the face seal to 14 medical and community mask models with the aim to understand the role of mask design and filter properties in air leakage. An instrumented head-form equipped with sensors for measuring volumetric airflow and differential pressure was used to simulate the air exhalation from the mouth of a person wearing a face mask. Results showed that the fraction of leaking air at the face seal is not negligible and can range from 10% to 95% according to mask model. The higher the exhaled airflow rate and the lower the amount of leaking fraction. A strong correlation was found between leaking fraction and filter breathability, indicating that a better breathability can lower air leakage. Highly breathable filtering materials should be employed in the production of medical and community face masks to maximize user comfort and minimize the fraction of exhaled air leaking unfiltered at the face seal. © 2022 IEEE.
ABSTRACT
COVID-19 pandemic caused several million deaths worldwide since the beginning of 2020. One of the most effective activities to contrast its diffusion is the execution of mass testing campaigns to track the virus spread. To design an efficient logistic system for such purpose, it is important to correctly plan the clinic layout and size the medical resources involved in the swab testing campaign, to avoid long patient queues or personnel underutilization. This paper describes the development of an original logistics simulation model to support the planning and design of clinics for the walk-in mass testing campaign against COVID-19 performed by South Tyrol Health Agency in just one weekend in November 2020 which involved more than 350’000 citizens. The developed model represents the targeted physical system considering all the different phase of such healthcare process. Furthermore, the duration of the multiple process phases is statistically distributed according to a large dataset collected during the COVID-19 testing campaign for touristic operators conducted in September and October 2020 in South Tyrol. The simulation model virtually evaluates the swab testing clinics with different parameters to determine the best scenario to be implemented. It concerns the number of medical resources allocated, the necessary clinic spaces and the time spent inside the clinic by each patient. The obtained results suggest that the so-defined configuration is distinguished by an average throughput of 8.8 minutes per patient. This clinic prototype has been replicated and set-up all over South-Tyrol territory to reach the targeted number of tested citizens. Indeed, 362’050 people were effectively tested from 20th to 22nd November 2020 leveraging 184 clinics and about 1400 healthcare co-workers, both medical and non-medical personnel. 3’615 Covid-positive people were detected and the virus transmission index of this Province fell from 1.22 to 0.74 just in the following 2 weeks. © 2021, AIDI - Italian Association of Industrial Operations Professors. All rights reserved.
ABSTRACT
Six Italian non-accredited laboratories participated to an interlaboratory study aimed at measuring Differential Pressure (DP) and Bacterial Filtration Efficiency (BFE) of three face-mask models using methods in-line with EN 14683 standard. Methodological non-conformities were annotated. Repeatability and reproducibility on quintuplicate samples were calculated according to ISO 5725-2. Sample stability was also assessed. Laboratories were ranked according to the total standard deviation over all samples and proficiency was evaluated using z-score according to ISO 13528. Although some non-conformities were present, performances for the DP measurements were always acceptable. One laboratory had to revise the bacterial suspension preparation for the BFE test. Overall, non-accredited laboratories working during pandemic emergency performed satisfactorily. Sample-to-sample variability impacted measurement repeatability. BFE values above 98% showed good repeatability (≤1.0%) and reproducibility (≤6.1%), but high BFE uncertainty was associated to community masks. Our findings suggest that relevant face-mask conformity standards should consider uncertainty of BFE and DP measurements. © 2021 The Authors