Filter integrity testing is a non-destructive method of evaluating whether a membrane filter remains within defined physical test limits. Depending on the membrane and filter configuration, integrity can be evaluated using methods such as Diffusion / Forward Flow, Bubble Point, Water Flow / Water Intrusion or pressure-based testing.
In critical pharmaceutical and biotechnology filtration, integrity-test acceptance criteria should not be treated as arbitrary instrument limits. They should correspond to the exact membrane-filter configuration and the validated filtration process. For sterilizing filtration, the physical integrity-test specification is normally established in relation to the filter's validated microbial-retention performance.
A membrane integrity test evaluates a measurable physical property of the installed filter. The result is compared with an acceptance limit defined for the specific membrane and filter configuration.
An integrity test can identify behaviour that falls outside the specified limits and may indicate membrane damage, an installation problem, an incorrect wetting condition or another issue affecting the filter system.
For critical membrane filtration, the relevant acceptance criteria should be established for the exact filter type and process. In sterilizing filtration, integrity-test specifications should correlate with the validated microbial-retention capability of the filter.
An integrity test verifies filter behaviour against defined physical limits. It does not by itself establish that an entire process, batch or finished product is sterile. Sterility assurance depends on the complete validated manufacturing process.
Different integrity tests measure different physical behaviour. The appropriate method depends on membrane wetting, membrane type, filter area, process application and the test specification defined for the filter.
| Test method | What is measured | Typical membrane / application direction |
|---|---|---|
| Diffusion / Forward Flow | Gas flow through a properly wetted membrane at a defined pressure below the Bubble Point. | Commonly used with suitable wetted membrane filters in critical liquid-filtration applications. |
| Bubble Point | Pressure behaviour associated with displacement of wetting liquid from the largest effective membrane pores. | Suitable wetted membrane filters where a validated Bubble Point specification is available. |
| Water Flow Test / WIT | Water movement or intrusion behaviour through a hydrophobic membrane under defined pressure conditions. | Suitable hydrophobic membrane filters, particularly selected PTFE gas and vent filters. |
| Pressure Hold / Pressure Decay | Change in pressure within a defined test system over time. | Filter or system testing where a validated pressure-based method and acceptance limit apply. |
| Combined Diffusion + Bubble Point | Diffusion behaviour followed by Bubble Point evaluation within one test sequence. | Compatible filter configurations where both parameters are part of the test specification. |
During a Diffusion or Forward Flow test, a suitably wetted membrane is subjected to gas pressure below its Bubble Point. Gas can dissolve in the wetting liquid, diffuse through the liquid-filled membrane structure and emerge downstream.
The measured flow is compared with the specified maximum value for the exact filter. Excessive flow can indicate loss of integrity or another condition that requires investigation.
Read the Diffusion / Forward Flow Guide →A Bubble Point test progressively increases gas pressure on the upstream side of a properly wetted membrane. At sufficient pressure, wetting liquid is displaced from the largest effective membrane pores and gas flow changes accordingly.
The measured result is compared with the applicable minimum Bubble Point specification for the filter configuration.
Read the Bubble Point Guide →Hydrophobic membranes such as suitable PTFE filters resist spontaneous wetting by water. A water-based integrity test can therefore evaluate water movement through or into the membrane structure under controlled test conditions.
In current Filtra integrity-testing terminology this is referred to as the Water Flow Test (WFT); the method has also been widely known as the Water Intrusion Test (WIT).
Read the Water Intrusion / WFT Guide →Pressure-based methods monitor pressure change within a defined test volume over a specified period. Depending on the configuration, this can be used to assess filter or system pressure behaviour.
Pressure Hold or Pressure Decay should not automatically be treated as interchangeable with membrane-specific Diffusion, Bubble Point or WFT testing. The method and acceptance criteria must match the validated application.
Many membrane integrity tests depend directly on the wetting condition of the membrane. Incomplete or inconsistent wetting can alter the measured result even when the membrane itself is physically intact.
Hydrophilic membranes such as suitable PES configurations can be wetted with an appropriate compatible liquid before tests such as Diffusion / Forward Flow or Bubble Point.
The wetting liquid, wetting procedure, temperature and filter specification can affect the test result. The validated procedure for the exact membrane filter should therefore be followed.
Hydrophobic membranes such as suitable PTFE filters naturally resist water wetting. Water-based WFT / WIT methods can therefore provide an integrity-testing route without first fully wetting the hydrophobic membrane with a low-surface-tension liquid.
The correct method still depends on the filter manufacturer's validated test specification and the actual process configuration.
For compatible applications, the it-02 and ita-02 platforms can be configured with optional automatic wetting equipment. Automated wetting controls the wetting sequence before integrity testing and can improve repeatability while reducing manual handling.
Separate wetting configurations can be used for capsule and cartridge filters according to the required setup.
Integrity-test timing depends on the manufacturing process, filter function, regulatory context and validated control strategy. Pre-use and post-use testing answer different questions and should not be treated as interchangeable.
A pre-use integrity test can verify that the installed filter is within its specified integrity limits before the filtration process begins.
The exact timing relative to sterilisation and installation depends on the process design and applicable requirements.
PUPSIT verifies the integrity of the sterilised filter assembly before use. This requires a process layout that allows the test to be performed while preserving the intended sterile downstream process.
In EU GMP Annex 1 applications, PUPSIT is specifically addressed for sterilizing filtration, together with risk-based provisions for situations where testing after sterilisation is not practically possible.
Post-use testing evaluates whether the filter remains within its defined integrity limits after the filtration operation and can detect loss of integrity that may have occurred during processing.
Both systems provide automated membrane integrity testing, but their physical format serves different workflows. The it-02 is a compact hand-portable tester; the ita-02 is a complete trolley-based mobile production workstation.
The it-02 is a compact approximately 11.5 kg integrity tester designed to be carried to the filter or test point. Battery and mains operation support flexible use across laboratories, cleanrooms and production locations.
Supported test functions include Diffusion / Forward Flow, Bubble Point, combined Diffusion + Bubble Point, Water Flow Test, pressure testing and volume measurement. Compatible capsule and other small-format filters can be tested directly.
View it-02 →
The ita-02 is an approximately 55 kg wheeled test system designed to be rolled between production stations as a complete integrity testing workstation.
It supports Diffusion / Forward Flow, Bubble Point, combined testing, WFT, pressure-based testing and upstream-volume measurement, with optional automatic wetting and other application-specific hardware.
View ita-02 →| Selection point | it-02 | ita-02 |
|---|---|---|
| Mobility | Hand-portable mobile tester | Wheeled mobile trolley system |
| Approx. weight | 11.5 kg | 55 kg |
| Typical movement | Carried to the test point | Rolled between production stations |
| Capsule testing | Yes | Yes |
| Battery operation | Yes | Yes |
| Automatic wetting | Optional configuration | Optional configuration |
| Best fit | Flexible laboratory, cleanroom and production testing where the tester is carried to the filter. | Routine multi-location production testing where a complete mobile workstation is preferred. |
Integrity testing must reflect the installed filter configuration. Capsule filters, cartridges in sanitary housings and filters integrated into single-use assemblies can require different connections, wetting methods, upstream volumes and test procedures.
Compatible capsule filters can be connected directly to the integrity tester or tested as part of a defined assembly. The correct test program should use the membrane-specific wetting procedure, pressure and acceptance limits.
Explore Capsule Filters →Membrane cartridges installed in sanitary housings can be tested through suitable upstream and downstream connections. System volume, venting, drainage and wetting all influence the practical test setup.
Explore Membrane Cartridges →In single-use systems, the filter can be integrated with tubing, connectors, bags and other process components. Integrity-testing access and venting should therefore be considered when the fluid path is designed, particularly where pre-use testing or PUPSIT is required.
Single-Use Bioprocess Solutions →In pharmaceutical and biotechnology environments, the test result is only one part of the integrity-testing workflow. Test-program control, traceable reports, equipment calibration, user procedures and qualification can also be important to the site's quality system.
Repeatable test programs reduce manual parameter entry and allow validated test settings to be associated with defined filter configurations.
it-02 and ita-02 support storage of more than 12,000 test results and can generate electronic records for review and archiving workflows.
Periodic calibration helps ensure that pressure and flow measurements remain within the specified performance of the instrument. Annual calibration is recommended for the current systems.
Qualification documentation and support can be incorporated according to the selected system and project requirements, including IQ/OQ documentation and PQ support.
Where electronic integrity-test records fall within a regulated electronic-record workflow, system selection should consider the site's requirements for record security, traceability, access control, review and retention.
The it-02 and ita-02 platforms are designed to support requirements associated with 21 CFR Part 11. Final compliance, however, depends on the complete validated system, procedures, user administration and quality environment in which the equipment is used.
Start with the filter and validated test procedure rather than with the instrument. The tester must support the membrane, test method, pressure range, physical connections, reporting workflow and production environment required by the application.
| Selection question | What to define |
|---|---|
| What filter is being tested? | Membrane material, capsule or cartridge format, filtration area, housing or assembly configuration and applicable filter specification. |
| Which test method is required? | Diffusion / Forward Flow, Bubble Point, WFT/WIT, pressure-based testing or a defined combination. |
| How must the membrane be prepared? | Wetting liquid, wetting procedure, temperature, venting, draining and any optional automatic-wetting requirement. |
| Where will testing take place? | Laboratory, cleanroom, production floor, mobile multi-location workflow or a hazardous-area installation requiring dedicated equipment. |
| How is the filter connected? | Direct capsule connection, tubing set, sanitary housing, single-use assembly or customised test interface. |
| What records are required? | Test reports, program control, electronic data, printer output, qualification documents and integration with site procedures. |
| What qualification is required? | Calibration, IQ/OQ documentation, PQ support, commissioning and operator training as applicable. |
Hazardous process environments involving solvents or potentially explosive atmospheres can require dedicated equipment designed for the applicable classified area.
Hydrophobic filter testing can require suitable pressure vessels, wetting equipment or specialised test arrangements according to the filter and selected procedure.
Capsules, sanitary housings and custom process systems can require different adapters, tubing sets and upstream or downstream connection arrangements.
Provide the filter type, membrane, filter size, applicable test limits, required test method, production environment and documentation requirements. Filtra can help evaluate the appropriate test setup and equipment configuration.
Filter integrity testing is a non-destructive procedure used to evaluate whether a membrane filter remains within defined physical test limits. The appropriate method and acceptance criteria depend on the membrane, filter configuration and validated application.
No. Integrity testing verifies filter behaviour against defined physical limits. In sterilizing filtration, those limits can be correlated with validated microbial-retention performance, but product sterility depends on the complete validated manufacturing process.
Diffusion or Forward Flow testing measures gas flow through a suitably wetted membrane below its Bubble Point. Bubble Point testing evaluates pressure behaviour associated with displacement of wetting liquid from the largest effective membrane pores. The applicable method and limits depend on the exact filter specification.
Water Flow Testing, historically also referred to as Water Intrusion Testing, is a water-based integrity-test method used with suitable hydrophobic membrane filters. It is commonly associated with hydrophobic PTFE gas and vent filtration applications.
Diffusion and Bubble Point measurements depend on the membrane being wetted according to the specified procedure. Incomplete or inconsistent wetting can alter the measured result even when the filter itself is physically intact.
PUPSIT means Pre-Use Post-Sterilization Integrity Testing. It refers to integrity testing of the sterilised filter assembly before the critical filtration process begins. Whether and how PUPSIT applies depends on the process and applicable regulatory requirements.
Post-use integrity testing can verify whether a critical filter remains within its specified integrity limits after filtration. The exact requirement and procedure should follow the validated process and applicable quality or regulatory requirements.
Yes. Compatible capsule membrane filters can be tested directly or as part of a defined filtration assembly using the appropriate membrane-specific test program, wetting procedure and acceptance limits.
Both are mobile integrity-testing systems. The it-02 is a compact hand-portable tester that can be carried to the test point. The ita-02 is a wheeled mobile trolley system designed as a complete production testing workstation.
Yes. The it-02 and ita-02 can be configured with optional automatic wetting equipment for compatible capsule or cartridge filter applications.
The it-02 and ita-02 are designed to support requirements associated with regulated electronic-record workflows, including requirements associated with 21 CFR Part 11. Final compliance depends on the complete validated system, procedures, user controls and applicable quality environment.
The current it-02 and ita-02 documentation recommends annual calibration. Site procedures, usage and quality requirements should also be considered when establishing the calibration programme.
