The role of filter breathability in reducing the fraction of exhaled air leaking from surgical and community face masks

Chiera, Silvia; Cristoforetti, Alessandro; Benedetti, L.; Borro, Luca; Mazzei, Lorenzo; Nollo, Giandomenico; Tessarolo, Francesco

doi:10.1109/memea54994.2022.9856516

Cited by 1 publication

(5 citation statements)

References 21 publications

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“…Experimental data showed that TFE increases at higher flow rates, coherently over all the tested masks. This behavior confirmed our previous results on a smaller number of mask models [27], and it is consistent with the opposite behavior observed for the fraction of air leaking at the face seal, that is reduced at higher flowrates [43], [58]. This is a consequence of the complementary role of Qmask and Qleak in (1) and the role of Qmask in the definition of Fmask (5) and TFE (6).…”

Section: Discussionsupporting

confidence: 91%

“…The surface response model confirmed this trend, producing a large negative linear coefficient associated to DP. This reinforced the concept that highly breathable materials can improve the mask efficiency, facilitating the passage of the airflow through the mask filter and avoiding leakages, supporting the results previously obtained by [43]. It is interesting to note that no significant difference in TFE existed between community and surgical masks, with some CMs (e.g., CM03) showed higher TFE values than many of the SMs tested in this study.…”

Section: Discussionsupporting

confidence: 88%

“…Indeed, although many CMs have moderately lower BFE values than a typical SM, most of them, in our mask sample, were also characterized by far lower DP values. As previously reported [43], breathability has a strong correlation with the fraction of airflow leaking at the face seal, since leakage is facilitated when the airflow encounters a high filter resistance [24], [60]. As leakage is complementary to Fmask, which is the dominant factor on TFE, a better breathability may significantly enhance TFE.…”

Section: Discussionmentioning

confidence: 58%

“…However, in the experimental conditions of Phase II, values of RII mask were determined by using (4) for 14 measurements of ΔPII and QII mask (every 10 L/min in the airflow range from 30 L/min to 160 L/min). To take into account minor variations of mask resistance at different air pressure, the analytical profile of RII mask as a function of ΔPII was modelled by fitting a first order polynomial curve on the calculated RII mask data, as previously detailed in [43]. Based on the linear regression model, the values of RI mask were predicted for the ΔPI corresponding to QI tot equal to 30 L/min, 90 L/min, and 160 L/min.…”

Section: Discussionmentioning

confidence: 99%

“…Since there is a lack of information on how the intrinsic variability among mask samples could affect measurement uncertainty, replicated measurements appear the most reliable experimental approach to estimate the confidence of any newly introduced mask performance parameter. This strategy has been pursued in previous pilot studies by Chiera et al for measuring leakage and the total filtration efficiency (TFE), mainly focusing on the influence of wearing styles and mask breathability on the overall mask performance [27], [43].…”

Section: Introductionmentioning

confidence: 99%

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Measuring Total Filtration Efficiency of Surgical and Community Face Masks: Impact of Mask Design Features

Chiera

Cristoforetti

Benedetti

et al. 2023

IEEE Trans. Instrum. Meas.

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Surgical and community face masks are used worldwide to reduce the transmission of respiratory infections in indoor environments. Performance parameters for these loosefitting devices are mainly focused on material filtering efficiency, while, differently from face respirators, there are no standards 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 flowrates. A significant positive correlation was found between TFE and filter breathability. The presence of a nosepiece showed to increase the TFE on average from 4 % to 6 %, according to the flowrate. 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 loosefitting face masks should carefully compromise between breathability and filtration efficiency of the filter materials. The addition of a metallic nosepiece help improving the TFE by limiting the air leaking at the face seal.

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