Table 1.

Evaluation of Reference and Common Materials’ Filtration Properties^a

material	source	structure	basis weight (g·m−2)	bulk density (basis weight/thickness) (g·m−2·μm−1)	initial filtration efficiency (%)	initial pressure drop (Pa)	filter quality factor, $Q$ (kPa−1)
Personal Protection Materials
polypropylene 1	particulate FFR	meltblown (nonwoven)	25	0.17	95.94 ± 2.00	9.0 ± 2.0	162.7 ± 21.3
polypropylene 2	medical face mask	meltblown (nonwoven)	26	0.21	33.06 ± 0.95	34.3 ± 0.5	5.0 ± 0.1
polypropylene 3	medical face mask	meltblown (nonwoven)	20	0.20	18.81 ± 0.50	16.3 ± 0.5	5.5 ± 0.1
Household Materials
polypropylene 4 (PP-4)	interfacing material, purchased as-is	spunbond (nonwoven)	30	0.26	6.15 ± 2.18	1.6 ± 0.5	16.9 ± 3.4
cotton 1 b	pillow cover	woven	116	0.57	5.04 ± 0.64	4.5 ± 2.1	5.4 ± 1.9
cotton 2 b	clothing (t-shirt)	knit	157	0.37	21.62 ± 1.84	14.5 ± 2.1	7.4 ± 1.7
cotton 3 b	clothing (sweater)	knit	360	0.45	25.88 ± 1.41	17.0 ± 0.0	7.6 ± 0.4
polyester	clothing (toddler wrap)	knit	200	0.38	17.50 ± 5.10	12.3 ± 0.5	6.8 ± 2.4
silk	napkin	woven	84	0.54	4.77 ± 1.47	7.3 ± 1.5	2.8 ± 0.4
nylon	clothing (exercise pants)	woven	164	0.70	23.33 ± 1.18	244.0 ± 5.5	0.4 ± 0.0
cellulose 1	paper towel	bonded	42.9	0.33	10.41 ± 0.28	11.0 ± 0.0	4.3 ± 2.8
cellulose 2	tissue paper	bonded	32.8	0.39	20.2 ± 0.32	19.0 ± 1.0	5.1 ± 3.2
cellulose 3	copy paper	bonded	72.8	0.76	99.85 ± 0.02	1883.6 ± 39.3	1.5 ± 0.2

^aAll materials were tested in samples of three unless denoted. Uncertainties denoted here represent the standard deviation between the samples. Materials in bold were further studied to investigate if the simple triboelectric charging can positively impact the filtration properties. For the particulate FFR sample, the meltblown is independently procured for usage in FFRs as it is difficult to obtain enough sample to test with the filter tester.

^bIndicates this sample did not have enough material and data is presented in samples of two.