Overview of integrity tester for sterilization grade filters

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Sterilization grade filtration is often used to remove microorganisms such as bacteria, ensuring the sterility of the final product. Integrity testing is a necessity for critical sterilizing grade filtration processes.

A series of integrity tests are usually carried out using an integrity tester to ensure the integrity of the filter cartridge, the hygienic sterility of the pharmaceutical industry, and the safety of the user’s life. In this article, we will analyze integrity testers and discuss how they work.

What is an integrity tester

What is an integrity tester?

Integrity Testers, also known as Cartridge Integrity Testers, utilize internationally recognized integrity testing technology to test and certify the integrity of cartridges used to filter liquids and gases in the pharmaceutical industry.

A series of integrity tests, including bubble point test, pressure retention test, diffusion flow test, water intrusion test to determine its filtration performance, can determine whether there are defects in the filtration material, whether the pore rate is in line with the specifications, is widely used in the pharmaceutical companies, filter material production enterprises.

Integrity testing technology in the pharmaceutical industry, filter integrity testing is a necessary requirement of the filtration process.

The U.S. Food and Drug Administration (FDA) in the aseptic product manufacturing guide (2004) clearly stipulates: “For a filtration system consisting of one or more filters, its validation should include microbial challenge testing and integrity testing under the worst conditions.”

Immediately after use, the integrity of a decontamination filter must be checked and documented using an appropriate method. Commonly used methods are the blistering point test, the diffusion flow test or the pressure retention test.

Preparation for integrity testing: wetting

Prior to integrity testing it is necessary to ensure that the test filter material has been fully wetted.

Manual wetting is generally accomplished by placing the filter material in the wetting solution for approximately 20 minutes, lifting the filter material every 3 minutes to remove air bubbles so that atmospheric pressure can press the wetting force into the membrane pores.

The product wetting solution is not water, nor a product or process fluid, but a solvent, and the results of integrity tests on the same filter material after product wetting may be different because of the difference in surface tension coefficients of the wetting solution.

The solubility and diffusivity of the test gas in the diffusion stream can also cause inconsistent results. For this system, the recommended wetting solution is a mixture of hydrocarbons, anhydrous ethanol, or 60% isopropanol and water.

Due to the molecular gravitational force of interfacial tension, the infiltrating liquid is firmly locked into the microporous interstices of the filter material.

Introduction to Test Procedures

Introduction to Test Procedures

There are many ways to test the integrity of a filter, and some common and effective tests are discussed below. Of course, no matter which test method you use, the test involves ensuring that the filter is properly wetted.

The fluid involved in wetting is usually water, except for hydrophobic filters, which use alcohol or water mixtures. This is shown below.

Bubble Point Test

When the gas pressure on the high-pressure side of the sample is greater than the capillary pressure and surface tension within the sample membrane pores released from the other side of the sample, the capillary pores of the wetting solution will be pressed out by the gas pressure to the sample of the low-pressure side of the pressure at this time the pressure on the high-pressure side of the sample that is regarded as the bubble point pressure, the phenomenon should be the sample appeared the first series of continuous bubbles.

Diffusion flow test

The forward flow diffusion test is mainly used by filter manufacturers as the final test before product release. In this method, a known gas is introduced into one side of the membrane and the time it takes for the gas to diffuse to the other side is measured. Unusually fast diffusion rates may indicate filter damage.

Holding Pressure Test

The Holding Pressure Test evaluates integrity by pressurizing the system and monitoring the change in pressure over time. This is a relatively simple integrity test for filters used in less critical applications. Using the same air/nitrogen source and an accurate pressure gauge, it calculates the pressure decay after a specified time interval, thus indicating potential leakage.

Water Intrusion Test

Water Intrusion Test

After the upstream pressure is stabilized, for intact filters, water upstream of the filter membrane intrudes into the membrane under pressure, water evaporates at the two-phase critical surface within the membrane, and the resulting water vapor will pass through the membrane to the downstream side of the filter so that the reduction in the amount of water upstream of the filter will result in a drop in pressure, and the tester can directly measure the gas flow rate required to maintain constant pressure upstream. Under normal operating conditions, filter integrity is confirmed when the measured flow rate is below the verified flow limit for this filter.

Benefits of the Integrity Tester

In the realm of quality control and testing, the Integrity Tester has emerged as a pivotal tool, offering a myriad of advantages for manufacturers and producers. Among its notable features, efficiency, high accuracy, non-invasiveness, and reliability stand out as key contributors to streamlining processes and ensuring the quality of production.


Sanitek’s S1.0 Integrity testers are able to quickly and accurately test gas tightness. In most cases, these testers can even automate the testing process, saving testers’ time and effort. This efficiency is vital for manufacturers and producers as it helps them save time and resources and increase productivity.

High Accuracy

Integrity testers are sometimes referred to as leak readers” because of their ability to detect very small leaks. This accuracy allows for more comprehensive testing of the airtightness of equipment or containers, thus ensuring the quality of the production process.


In the past, many equipment or vessel leak testing methods required destructive testing. Such testing methods not only tend to damage the test object, but also affect its operation and function. However, integrity testers do not require destructive testing. They can be mounted non-intrusively next to or above the test object and scan the test area to test the airtightness of the equipment or container. This test method is very useful in maintaining the integrity of the test object and is ideal for testing large, complex or inaccessible equipment or containers.


Integrity testers often use digital technology and algorithms to analyze and evaluate test results. This approach provides testers with reliable test results, allowing manufacturers and producers to control the quality of their products with greater confidence.

Wide range of industries

Integrity Testers are used in a wide range of industries to ensure the tightness and performance of equipment, containers or systems. Integrity testers play a key role in pharmaceutical, food and beverage, chemical, medical device manufacturing, aerospace and electronics manufacturing.


Integrity testers are often used to carry out a series of integrity tests to ensure the integrity of the cartridge, the hygienic sterility of the pharmaceutical industry, and the safety of the user’s life.

Sanitek Filter is a trusted filter manufacturer. Our team of professionals will identify the right integrity tester for your process and provide assistance with installation, training and validation as needed. Please contact us for more details on integrity testing.

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