One of the oldest and most intuitive leak tests is the bubble test. The package is placed into a chamber filled with water. In basic applications the package is simply compressed. Using modern bubble test devices, the head space is evacuated, the package inflates and leaks become visible as a stream of bubbles.

Suitable for
Modified atmosphere packages or packages with compressed air; vacuum packages (with optional equipment, e.g. LEAK-MASTER^® EASY by WITT)

Pros
Intuitive use
Low initial costs
Localisation of the leak

Cons
Limits when detecting microleaks
Possibility of human error
Destructive test, package can’t be sold after testing
No digital documentation for quality assurance

>LEAK-MASTER^® EASY leak testing

Widely used for leak testing of modified atmosphere packaging (MAP) are devices that operate with test gases. Solutions for sample or in-line leak testing are available. In either case the test product is placed in a test chamber, and the chamber is evacuated. In the event of a leak, gas flows from the modified atmosphere package. Highly sensitive gas sensors detect even the smallest leaks with measurements taken within a few seconds. The package will not be damaged, and with modern equipment, the operation is simple. Furthermore, all leak test data, e.g. date, time, name, product and tester, is recorded and digitally archived for documentation purposes.

CO₂ is a suitable trace gas, as it is already included in most modified atmosphere packages. Alternatively, helium or hydrogen can be used to detect very small leaks. However, both must be introduced into the packaging and are expensive and complicated to handle. The use of hydrogen as test gas also complicates the residual oxygen measurement, as the oxygen test devices are usually sensitive to hydrogen.

Using test gases also allows in-line leak detection. Market leading CO₂-based leak test devices offer a test frequency of up to 15 cycles per minute.

Suitable for
Modified atmosphere packages or packages with compressed air.

Pros
Short measurement time
Detection of microleaks
Non-destructive leak testing
In-line testing with 100%-control
Intuitive operation
Full digital documentation of quality assurance

Cons
No localisation of the leak

>LEAK-MASTER^® PRO leak testing
>LEAK-MASTER^® MAPMAX leak testing

The pressure differential test (or pressure-rise method under vacuum) also depends on air or gas inside the package. The product is placed in a chamber, and the chamber is evacuated. If there is a leak, gas will escape from the package. In contrast to the trace gas method, the sensor does not directly detect the gas, but only a change in pressure in the test chamber. This method can be used only for sample leak testing. Digital documentation is possible.

Suitable for
Modified atmosphere packages or packages with compressed air

Pros
Short measurement time
Non-destructive leak testing
Full digital documentation of quality assurance

Cons
No localisation of the leak
No in-line testing possible
Selection of the appropriate test method

To select a suitable method for leak testing, the following questions have to be answered:

• What type of packaging is to be leak tested? For example: vacuum packaging, modified atmosphere packaging (MAP), packs with compressed air
• Is a non-destructive leak test required?
• Is enough gas inside the package?
• What detection limit is required? What leak size has to be determined?
• Is sample leak testing or in-line leak detection required?

When is a package really leak-tight? There is no clear answer to this question. Various overviews of leak-tightness classes provide different definitions of leak-tightness. More important is the question: How leak-tight must your packaging be? The answer depends on a complex combination between packaging, product and desired shelf life.