For gas filtration in a vent application, YES, Pall sterilizing grade gas filters can be used in both directions.
For gas filtration, Pall offers the following sterilizing grade gas filters:
Emflon® II V002PV
Acro® 50 (6074270)
These filter devices feature a symmetrical filter media construction, where two layers of membrane of the same pore rating are used in the manufacturing of the final filter cartridge or capsule.
When a filter of a symmetrical media construction is used for venting purposes, in either forward or reverse flow direction, the gas flow and any contaminants will travel through a torturous path of the same characteristic and length as in the forward direction. This will lead to the same retention efficiency in either flow direction.
Based on the symmetric media construction the filter will thus act as a sterile barrier when venting in either flow direction. Therefore, Pall Emflon® II V002PV, Emflon PFR, Emflon HTPFR, Acro® 50 (6074270) and Acrodisc® KM292HP filters can be used for bi-directional flow applications under this venting mode of filtration.