Bubble Leak Test for Packaging under ASTM F2096 and D3078
By Lim Xu, Export Manager
A bubble leak test finds gross leaks in a package by creating a pressure difference across the package wall and watching for bubbles under liquid. ASTM F2096 and ASTM D3078 describe the two common ways to set up that pressure difference.
What is a bubble leak test?
A bubble leak test is a visual check. Gas inside the package escapes through a leak path and shows up as a steady stream of bubbles in the surrounding water or test fluid.
Both ASTM methods are written for gross leaks, not fine leaks. F2096 covers the detection of gross leaks in packaging, and D3078 covers gross leaks in flexible packaging that contains a headspace gas.
The bubbles also show where the leak is. Marking that spot helps when you trace a fault back to a seal, a channel or a hole in the material.
ASTM F2096 and ASTM D3078 compared
The two methods create the pressure difference from opposite sides of the package wall. F2096 raises the pressure inside the package, while D3078 lowers the pressure around it.
| Point | ASTM F2096 | ASTM D3078 |
|---|---|---|
| How the pressure difference is made | Air is fed into the package while it is under water | A vacuum is drawn over the package in a transparent chamber |
| Packages named in the scope | Tray and pouch packages | Flexible packaging that contains a headspace gas |
| Stated sensitivity | Down to 250 µm (0.010 in.) with an 81 % probability | Limited to 1 × 10⁻⁵ atm cm³/s, or less sensitive |
F2096 also notes that its sensitivity has not been evaluated for porous materials other than spunbonded polyolefin, or for nonporous packaging. Keep that in mind before you use its sensitivity value for another material.
D3078 relies on the gas already inside the pack. A package with little or no headspace gives the method very little gas to form bubbles.
Questions about a model or a test? Email Amy Zhao, Export Manager, at [email protected].
Running the test step by step
For the D3078 vacuum method, the chamber needs a vacuum-tight cover, a vacuum gauge, an inlet from the vacuum source and an outlet to atmosphere. D3078 sets out the full test procedure, so follow the standard for the actual test. The steps below are a general outline of a vacuum bubble test, not a copy of D3078:
- Let the packages and the immersion fluid reach normal room temperature.
- Use an immersion fluid that does not degrade the package.
- Hold the package under the fluid in the transparent chamber and close the cover.
- Draw the vacuum to the level and for the time set in your procedure.
- Watch the package for bubbles during the hold, then vent the chamber.
- Record what you see for each package, including where bubbles appeared.
For the F2096 method, an air supply is put into the package and the package is held under water. It is then inflated to a predetermined pressure while the operator looks for a steady stream of bubbles.
Test laboratories commonly establish the minimum test pressure for each package before routine testing. In lab practice, higher pressure tends to make the test more sensitive, and lower pressure makes it less sensitive.
Our MFY-01 vacuum seal tester runs the ASTM D3078 bubble emission method in a vacuum chamber.
How sensitive is a bubble test?
ASTM D3078 puts its sensitivity limit at 1 × 10⁻⁵ atm cm³/s (1 × 10⁻⁶ Pa m³/s). It adds that an interlaboratory test showed the method can be even less sensitive than that.
D3078 also warns that small leaks may not be detected. Viscoelastic effects in the product or trapped air can block a small opening, and product pushed by the pressure inside the pouch can plug a small leak.
The size of leak you can find depends on the product inside, the packaging material and the test parameters you choose. A setting that works for one pack does not prove the same sensitivity on another.
For F2096, the scope gives a sensitivity down to 250 µm (0.010 in.) with an 81 % probability. Both values describe gross leaks, so treat a bubble test as a screen for larger defects.
If you need to look for smaller leaks, compare other methods as well. Our article on the vacuum decay leak test explains one pressure based option.
Limits of the bubble method
USP <1207> sorts leak test technologies into deterministic and probabilistic groups. It prefers deterministic methods when other method selection criteria allow.
The chapter also makes clear that no one leak test suits every package. A leak test method is developed for a specific package and product, then confirmed in validation.
Before you rely on a bubble test, check these points:
- The package holds enough gas to form bubbles under the test conditions.
- The pressure or vacuum level has been set with packages of known condition.
- The operator can see the whole package surface through the fluid.
- The defect size you need to find is within the gross leak range.
Frequently asked questions
Is a bubble leak test destructive?
ASTM F2096 is destructive, because the package has to be entered to supply the internal air pressure. ASTM D3078 tests the closed package inside a vacuum chamber, so no entry into the package is needed for the test itself.
Can ASTM F2096 be used on large or unusual packages?
ASTM F2096 says it may suit large or long packages that cannot go into the apparatus of other package integrity methods. It also calls the method extremely useful in a test laboratory where no common package material or size exists.
Talk to our factory team
We sell direct from our factory, so you work directly with our factory team. Questions about a model or a test? Email Amy Zhao, Export Manager, at [email protected].