Correction

This article refers to:

Designing better cloth masks: The effect of fabric and attachment-style on discomfort

Article title: “Designing Better Cloth Masks: The Effect of Fabric and Attachment-Style on Discomfort”

Authors: J. Mumma, F. Liu, N. L. Ng, J. Morgan, L. Morgan, and P. Gannon

Journal: Journal of Occupational and Environmental Hygiene

Bibliometrics: Volume 20, Number 1, pages 23–32

DOI: https://doi.org/10.1080/15459624.2022.2145013

Tables 1 and 2 were published with incorrect pressure drop results, affecting discussion of the reported data in the “Results and discussion” and “Discussion” sections of the article.

Table 1. Filtration efficiency and pressure drop for unwashed samples of fabric.

Fabric	Overall filtration efficiency (%)	Pressure drop (Pa)	Pressure drop (mmH2O)
Flannel	64	220	22.4
Muslin	27	100	10.2
Twill	50	250	25.5
Quilter	34	170	17.3
Poplin	39	200	20.4

Table 2. Comparison of filtration efficiency and pressure drop after 1 and 10 washing and drying cycles.

Fabric	Number of washing/drying cycles	Overall filtration efficiency (%)	Pressure drop (Pa)	Pressure drop (mmH2O)
Flannel	1	80	360	36.7
	10	77	250	25.5
Twill	1	63	260	26.5
	10	62	250	25.5

The correct versions of Tables 1 and 2 and the affected text are reproduced.

Results and discussion

Table 1 shows the results for the unwashed samples of cotton fabric. Out of the five samples, flannel had the highest overall filtration efficiency (M = 64%; SD = 1%), followed by twill (M = 50%; SD = 1%). These results are consistent with previous studies showing that three-layered material samples have an overall filtration efficiency of approximately 50% for sub-micron particles (Joo et al. 2021). Although pressure drops measured in this work are also comparable to previous studies using multi-layered samples (Hao et al. 2020; Drewnick et al. 2021; Joo et al. 2021), all unwashed samples, except muslin, exceeded the ASTM F3502-21 recommended limit of 15 mmH₂O (Table 1) for airflow resistance in barrier face coverings.

Table 2 shows the filtration efficiency and pressure drop of the highest performing fabrics after being washed once (1×) and washed ten times (10×). For flannel, the filtration efficiency of the sample increased by 13% and 16% for the 1x and 10x washed samples, respectively. For twill, the filtration efficiency increased by 12% and 13% for the 1× and 10× washed samples, respectively. The increased efficiency (Higgins et al. 2003) is likely to be attributable to changes in the material area density or microscopic structures from washing and drying. However, the pressure drop of both fabrics after being washed 1× and 10× again exceeded the ASTM F3502-21 recommended limit of 15 mmH₂O (Table 2). Although no fabric achieved a high filtration efficiency without a high pressure drop, we retained flannel and twill to assess the effect(s) of fabric on user discomfort and behavior in Study 2 as flannel (36.7 mmH₂O) and twill (26.5 mmH₂O) differed markedly in pressure drop after one laundering cycle (Table 2).

Discussion

Cloth masks have been used to reduce community transmission during the current pandemic and can be used during future outbreak situations. Although not as effective as other types of masks, such as tight-fit-ting respirators (e.g., N95s; Andrejko 2022), cloth masks offer greater protection than wearing no mask at all (Lindsley et al. 2021) and have the unique advantages of being easily accessible to the public, affordable, and reusable (CDC 2022). However, little attention has been paid to the impact of mask designs on their effectiveness as source control (Bhattacharjee et al. 2020; Liao et al. 2021). In the present studies, two common design parameters of cloth masks were varied to ascertain their effect(s) on the subjective discomfort and frequency of problematic mask-wearing behaviors, which detract from the effectiveness of cloth masks as source control.

These findings have both practical and scientific significance; regarding the former, results of human subjects testing showed that adults found masks made of flannel or twill to be similarly breathable, whereas children found flannel to be more breathable than twill. However, children touched their masks more frequently when wearing flannel masks. For adults, ear loops were less comfortable than ties and were more often associated with greater face- and mask-touching. Thus, the use of ties (rather than loops) is generally supported whereas flannel or twill were both comparable for adults, but neither fabric was clearly better for children. These recommendations should be balanced with how these design decisions affect mask performance (i.e., outward-leakage), which the present studies did not assess.