Table 1.

Summary of recent research on filtration efficiency for different layer of face mask

Sr. no	Mask type	Material	Layers	Filtration efficiency (%)	Reference
1	Commercial 3-ply mask	Polypropylene filter layer	Single	76 ± 22	[13]
2	3-ply face mask modified into respirators	Polypropylene and Halyard Quickcheck H300	Single layer	70.08 ± 0.48	[17]
			Double layer	86.60 ± 1.91
			Triple layer	93.84 ± 0.37
3	Fabric mask	Quilter’s cotton (80 TPI),	Single	9 ± 13	[18]
			Double	38 ± 11
		Cotton (600 TPI),	Single	79 ± 23
			Double	82 ± 19
		Natural silk	Single	54 ± 8
			Double	65 ± 10
			Quadruple	86 ± 5
4	Nanofibrous filters	Polyvinylidene fluoride (PVDF) electrospun filter	Single	≥ 95.7	[19]
5	N95 respirator	Polypropylene filter layer	Single	94.4	[20]