Table 3.

Loss of filtering efficiency after 4 months of samples stored at room temperature (0.5–1.0 $\mathsf{\mu }$m and 1.0–0.0 $\mathsf{\mu }$m).

Particle Diameter Range 0.5–1.0 $\mathsf{\mu }$m                    Particle Diameter Range 1–10 $\mathsf{\mu }$m
Sample	Thickness ($\mathsf{\mu }$m)	Filtration Efficiency (%) 1	Filtration Efficiency (%) 2	Loss of Efficiency (%) 2	Filtration Efficiency (%) 1	Filtration Efficiency (%) 2	Loss of Efficiency (%) 2
M1	230	98.1	96.3	1.7	99.9	99.8	0.1
M2	210	96.5	92.5	4.0	99.9	99.8	1.1
M3	110	93.1	86.1	7.0	98.3	98.5	0.0
M4	110	95.2	82.4	12.8	99.7	97.8	1.9
M5	100	89.5	85.5	4.0	97.2	98.2	0.0
M6	190	93.9	82.5	8.5	98.8	98.6	0.2

¹ Initial values. ² After 4 months.