Fitted filtration efficiency and breathability of 2-ply cotton masks: Identification of cotton consumer categories acceptable for home-made cloth mask construction

Abstract

The objective of this study was to characterize commercially-available cotton fabrics to determine their suitability as materials for construction of cloth masks for personal and public use to reduce infectious disease spread. The study focused on cottons because of their widespread availability, moderate performance and they are recommended for inclusion in home-made masks by international health authorities. Fifty-two cottons were analyzed by electron microscopy to determine fabric characteristics and fabric weights. Sixteen fabrics were selected to test for breathability and to construct 2-ply cotton masks of a standard design to use in quantitative fit testing on a human participant. Cotton mask fitted filtration efficiencies (FFEs) for 0.02–1 μm ambient and aerosolized sodium chloride particles ranged from 40 to 66% compared with the mean medical mask FFE of 55±2%. Pressure differentials across 2-ply materials ranged from 0.57 to > 12 mm H2O/cm2 on samples of equal surface area with 6 of 16 materials exceeding the recommended medical mask limit. Models were calibrated to predict 2-ply cotton mask FFEs and differential pressures for each fabric based on pore characteristics and fabric weight. Models indicated cotton fabrics from 6 of 9 consumer categories can produce cloth masks with adequate breathability and FFEs equivalent to a medical mask: T-shirt, fashion fabric, mass-market quilting cotton, home décor fabric, bed sheets and high-quality quilting cotton. Masks from one cloth mask and the medical mask were re-tested with a mask fitter to distinguish filtration from leakage. The fabric and medical masks had 3.7% and 41.8% leakage, respectively. These results indicate a well fitted 2-ply cotton mask with overhead ties can perform similarly to a disposable 3-ply medical mask on ear loops due primarily to the superior fit of the cloth mask which compensates for its lower material filtration efficiency.

A systematic review of passing fit testing of the masks and respirators used during the COVID-19 pandemic: Part 1-quantitative fit test procedures

“…Thirteen studies reported that there were significant differences in passing fit test rates of masks or respirators [ 39 – 41 , 65 , 69 , 77 , 94 , 108 , 111 , 127 – 131 ]. In the study by Martelly et al, the significant level was not reported; however, due to the considerable difference between the two studied respirators, it could be considered as a statistically significant difference in terms of FF (7.0 vs. 143) [ 129 ].…”

“…Also, it seems that the respirator model or brand must be considered as one of the factors influencing fitting characteristics in order to ensure optimal respiratory protection for the users. For example, in the study by Drouillard et al [ 39 ], the average FFE of the control medical mask (55.3%) was lower than that of the fabric mask (64.97%), whereas the Bandana masks exhibited lower FFEs (39.8%-48.1%). It would appear that the material characteristics, such as fabric weight and pore size were significant factors influencing FFE.…”

Advanced and Smart Textiles during and after the COVID-19 Pandemic: Issues, Challenges, and Innovations

“…At the same time, further research showed that non-woven materials commonly provided better air permeability and filtration efficiency combined than woven materials alone [ 22 ], as well as strong resistance to mechanical or sweat exposure [ 23 ], which explains the wide application of melt-blown non-woven fabrics in air filtration [ 24 ]. A quality factor and other models based on structural parameters of woven textiles were developed, which indicated that nanofibers in a less densely packed formation achieve an optimal compromise of both values, as opposed to the macro-fibrous structure of typical woven textiles [ 25 , 26 ] ( Figure 1 B). Certainly accelerated by the pandemic, electrospinning and similar methods were identified as promising techniques to produce nanofibrous filter materials, which not only satisfy the filtration efficiency and permeability criteria [ 20 , 27 , 28 , 29 ] but also offer other benefits, such as transparency [ 30 ], reuse after washing or disinfection [ 31 , 32 ], and antimicrobial or antiviral functionalization [ 33 , 34 , 35 ].…”

Physiological Workload Analysis on the Use of Face Masks during Physical Activities

“…Furthermore, cloth masks are usually made from various types of woven and non-woven fabrics, which have lower filtration standards and breathability requirements. The filtration efficiency of the mask depends on the diameter of the fiber or yarn, the tightness of the weave, and manufacturing process [13].…”