. 2021 Mar 17;16(3):e0247575. doi: 10.1371/journal.pone.0247575

Table 1. Preliminary testing of filtration systems (42 CFR Part 84 (30 L/min)).

System		Seal Resistance (kPa)^†	Expected (kPa)	Particles passed (count/cm³) ^*	Flow constant (L/min)
Mask	Filter	Seal Resistance (kPa)^†	Expected (kPa)	Particles passed (count/cm³) ^*	Flow constant (L/min)
SFM	3M 5N11–2 ply	-1.3	< -250	1288	30 +/- 4
SFM	3M 5N11–2 ply	-1.0	< -250	2040	30 +/- 4
SFM	3M 5N11–3 ply	-2.5	< -250	3495	30 +/- 4
Sewn Mask	Halyard H400–2 ply	-4.2	< -250	271	30 +/- 4

†The expected seal resistance is negative, with < -250 kPa indicating an adequate seal.

*The no. of particles passing through in an ideal filtration system is < 20 per cubic cm in volume.