Table 2.

Loss of filtering efficiency after 4 months of samples stored at room temperature (0.01–1.0 $\mathsf{\mu }$m particle size range).

Particle Diameter Range 0.01–1.0 $\mathsf{\mu }$m
Sample	Thickness ($\mathsf{\mu }$m)	Filtration Efficiency (%) 1	Pressure Drop (mbar) 1	Filtration Efficiency (%) 2	Pressure Drop (mbar) 2	Loss of Efficiency (%) 2	Filtration Efficiency (%) 3	Pressure Drop (mbar) 3	Loss of Efficiency (%) 3
M1	230	89.9	0.80	87.8	0.86	2.4	87.4	0.88	2.9
M2	210	85.5	0.64	85.1	0.76	0.5	80.9	0.68	5.4
M3	110	78.85	0.40	77.1	0.52	2.2	59.3	0.66	24.8
M4	110	76.6	0.42	65.0	0.36	15.0	63.1	0.70	17.5
M5	100	71.2	0.40	67.7	0.42	4.9	58.3	0.64	18.1
M6	190	82.5	0.46	70.0	0.46	15.2	63.5	0.70	23.0

¹ Initial values. ² After 2 months. ³ After 4 months.