Table 3.

Comparison of the filtration performance of masks made of different materials [16]

Sample	Flow rate: 1.2 CFM
	Filter efficiency (%)		Pressure differential
	< 300 nm average ± error	> 300 nm average ± error	ΔP (Pa)
N 95	85 ± 15	99.9 ± 0.1	2.2
Surgical mask	76 ± 22	99.6 ± 0.1	2.2
Cotton quilt	96 ± 2	96.1 ± 0.3	2.7
Quilter’s cotton (80TPI), 1 layer	9 ± 13	14 ± 1	2.2
Quilter’s cotton (80TPI), 2 layers	38 ± 11	49 ± 3	2.5
flannel	57 ± 8	44 ± 2	2.2
Cotton (600TPI), 1 layer	79 ± 23	98.4 ± 0.2	2.5
Cotton (600TPI), 2 layers	82 ± 19	99.5 ± 0.1	2.5
Chiffon, 1 layer	67 ± 16	73 ± 2	2.7
Chiffon, 2 layers	83 ± 9	90 ± 1	3.0
Natural silk, 1 layer	54 ± 8	56 ± 2	2.5
Natural silk, 2 layers	65 ± 10	65 ± 2	2.7
Natural silk, 4 layers	86 ± 5	88 ± 1	2.7
Cotton/chiffon	97 ± 2	99.2 ± 0.2	3.0
Cotton/silk	94 ± 2	98.5 ± 0.2	3.0
Cotton/flannel	95 ± 2	96 ± 1	3.0

TPI = Threads per inch