Bubble testing is a widely used method to detect leaks and determine the integrity of a package. This method is commonly used in various industries such as healthcare, food, and pharmaceuticals to ensure that the package contents reach their destination without any damage or contamination. Bubble testing involves submerging a package in water and observing for bubbles, indicating a leak or breach of the sterile barrier.

Now when you hear the phrase “bubble testing,” a specific technique might immediately come to your mind. But what bubble testing actually is and means can vary drastically by industry and product.

There are different types of bubble testing techniques, such as bubble emission testing, direct-pressure, and vacuum-box technique. Each one is very different from the other, and we’ll cover what each of those methods are in this article. It is important to use the right type of bubble testing for specific applications to ensure accurate and reliable results.

What is Bubble Emission Testing?

Bubble emission testing, also known as bubble leak testing, is a non-destructive, whole-package integrity test that can quickly identify leaks in flexible and rigid packaging, such as Tyvek pouches or thermoformed trays.

At a scientific level, bubble emission testing is a method used to detect leaks in flexible packaging materials such as bags, pouches, and plastic films. The test involves placing the sample in a water-filled vacuum chamber and creating a pressure differential between the inside of the package and the surrounding vacuum chamber.

To create the pressure differential, the Vacuum Chamber is drawn into a vacuum, and the pressure drops atmospheric levels. The package is at (or around) Atmospheric pressure, and is now at a higher pressure level than the Vacuum Chamber.

If there is a leak in the package, the higher pressure air/gas inside the package will escape through the leak into the lower pressure vacuum chamber. Since the Vacuum Chamber is filled with water, air bubbles will form at the location of the leak.

This test is commonly used for evaluating the sterile barrier integrity of packages and is an essential component of validation activities. Bubble emission testing can help ensure that packages are protected during transit or storage, making it an important quality control step for many manufacturers.

Benefits of Bubble Testing

It Identifies the Location of Leaks

Bubble testing is a highly effective method for identifying leaks in packages. It offers several advantages over other testing methods, including the ability to identify the location of a leak, not just the presence of a leak. This is a critical benefit because it enables manufacturers to quickly locate the source of the problem and take corrective action, reducing waste and increasing product quality.

It’s Fast

In addition to its ability to pinpoint the location of leaks, bubble testing is also incredibly fast. In some cases, the test can be completed in less than 30 seconds. This is a significant advantage for manufacturers who need to test large numbers of packages quickly and efficiently. Bubble testing can be easily automated, which further reduces the time and cost of testing.

It’s Versatile

Another benefit of bubble testing is its versatility. The method can be used to test a wide range of package types, including bottles, tubes, and bags. This means that manufacturers can use a single testing method for all of their packaging needs, simplifying the testing process and reducing costs.

It’s Non-Destructive

Furthermore, bubble testing is a non-destructive method of testing. This means that packages can be tested without damaging them, allowing manufacturers to test a representative sample of their products without sacrificing quality or wasting materials.

What Bubble Testing is Not

It’s important to note that bubble testing is not limited to package leak detection. Direct-pressure and vacuum-box techniques, for example, are used for leak testing on components like piping systems and tanks. At FlexPak, however, our equipment is specifically designed for package leak detection using the bubble emission test (ASTM 3078).

This test requires any part or package to be placed inside the leak detector, making it unsuitable for testing large piping systems such as weld inspection testing. We at FlexPak prioritize continuous improvement and a package-first approach, ensuring that customers have the right equipment for their unique package designs.

Direct-Pressure Technique

Bubble testing is often associated with package leak detection, but there are other forms of bubble leak testing as well. The direct-pressure technique is one such method that involves pressurizing a component with gas and submerging it in a solution or applying a solution to the outside. If there is a leak, bubbles will form because the leaking gas passes through the solution. This technique is commonly used on piping systems to find leaks in threaded connections and welds.

Vacuum-Box Technique

Another common form of bubble leak testing is the vacuum-box technique, which is used on components where access to one side of the weld is obstructed and cannot be directly pressurized. In this technique, a solution is applied to a pressure-boundary surface, and a differential pressure is created across it, leading to bubble formation if there is a leak. One of the most common applications of this technique is to test the welds of tank floors.


Bubble emission testing is a critical part of ensuring package integrity during transit or storage. At FlexPak, our expertise and equipment provide high-quality package leak detection services that are designed to meet the unique needs of each customer. By using the bubble emission test, you can quickly and accurately identify leaks in your packages, ensuring that they are protected and secure.