There is no general rule to this and depends on the filter application.

The user should qualify the filter change-out frequency for their specific application, but this should never exceed Pall claims for cumulative sterilization cycles and/or the maximum differential pressure.  These specificationswere established by Pall in controlled laboratory conditions with filters that were not exposed to any process (including manufacturing or production) conditions.

The filter lifetime and change-out should be based on a risk assessment by the user for their specific application including relevant validation/qualification data.

For example, the impact of a post-use integrity test failure of the filter should be considered.

For gas filtration in compressed gas, tank vent, or utilities setting, industry best practice is to replace the filter under a pre-defined preventative maintenance schedule (i.e. at a minimum of 12-month cycle).

For critical applications, single use is recommended to eliminate the risks of cross contamination between batches.

For more information, please see Pall Publication:

USTR2660 Considerations Re-Use Sterilizing-Grade Filters

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

Emflon PFR

Emflon HTPFR

Acro® 50 (6074270)

Acrodisc® KM292HP

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.

Pall manufactures different membrane filters for gas filtration. We use either Polytetrafluoroethylene (PTFE) filter membrane or Polyvinylidene Fluoride (PVDF) modified, for such a purpose.

In our Pall Allegro™ single-use systems, the method to sterilize these systems is by gamma irradiation.

The Polytetrafluoroethylene (PTFE) filter membrane, is incompatible with gamma irradiation, so it could not be used as a gas filter in our Single-Use Systems.

The Polyvinylidene Fluoride (PVDF) modified is compatible with gamma irradiation and for this reason is the device to be used with our Single-Use-Systems.

Pall Emflon II V002 sterilizing grade filters uses a filter membrane made of polyvinylidene difluoride (PVDF).

Pall Emflon® HTPFR filter cartridges are specifically designed for the sterile filtration of gas in critical applications in the biopharmaceutical and biotechnology industries, where the following environmental conditions maybe present:

High-temperature applications where the gas to be filtered exceeds 60ºC in continuous operation, including autoclave, fermentation inlet air, aseptic packaging/blow-fill-seal and hot Water For Injection (WFI) tank vents.

Ozonated-water tank vent applications

Oxygen-enriched applications in fermenter or bioreactor applications where improved aeration enables higher product yield.

Pall Emflon® HTPFR incorporate a double-layer (0.2 μm) of inherently hydrophobic, Pall-manufactured polytetrafluoroethylene (PTFE) membrane. The polypropylene hardware is specially formulated with protective anti-oxidants and the filter’s support and drainage layers are made of polyphenylsulphide (PPS) polymer to minimize combustibility. Oxidation-resistant membrane and cartridge components allow extended use in air/vent service up to 100°C and for shorter periods up to 120°C.

For more information, please see Pall Publications:

Safety Considerations for Gas Filtration in High-Temperature and Oxygen Enrichment Applications
Sterile Vent Filtration on Ozonated Water Tanks
Sterilizing Filtration of Enriched and Pure Gaseous Oxygen Employed in Cell Culture Applications