Seal Integrity Testing: Why It Matters and How It Prevents Leaks

Sealing technology plays a critical role in industrial and consumer packaging. From medical devices to food packaging, seals are responsible for preventing leaks, maintaining sterility, and protecting product quality throughout distribution.

Because so much responsibility rests on a small sealing area, even minor defects can have outsized consequences. That’s why seal integrity testing exists — to verify that a package remains fully sealed under real-world conditions, not just in theory.

Seal integrity testing sits at the core of modern package integrity testing programs, helping manufacturers catch failures before they become recalls, compliance issues, or safety risks.

Why Seal Integrity Testing Is So Important

Seal integrity testing allows defects to be detected early — before products leave the facility or reach consumers. In regulated industries like healthcare and pharmaceuticals, this testing is essential for verifying sterile barrier systems and ensuring patient safety.

For example, in medical packaging, even microscopic seal leaks can compromise sterility. That’s why seal integrity testing is a foundational requirement in sterile barrier system testing and ISO-compliant packaging programs.

Beyond defect detection, seal integrity testing also supports:

• Regulatory compliance
• Brand protection
• Shelf-life validation
• Recall prevention

In food packaging, it plays a key role in HACCP programs, where leak detection often serves as a critical control point.

Seal Integrity vs. Seal Strength: An Important Distinction

Seal integrity and seal strength are often confused — but they measure very different things.

• Seal strength measures how much force a seal can withstand before separating.
• Seal integrity measures whether the seal prevents leaks under expected conditions.

A seal can be strong but still leak. Conversely, a seal can maintain integrity without having extreme peel strength. This distinction is explained further in our breakdown of seal integrity vs. seal strength — and it’s why integrity testing is essential even when seals pass strength tests.

Common Seal Integrity Testing Methods

Different packages, products, and industries require different testing methods. The right approach depends on package design, product sensitivity, and applicable ASTM or ISO standards.

Below are some of the most widely used seal integrity testing methods.

Bubble Leak Testing (ASTM D3078)

Bubble leak testing is one of the most common visual methods for detecting seal failures.

The sealed package is submerged in water inside a vacuum chamber. When vacuum is applied, air escapes through any compromised areas, forming visible bubbles. This method is effective for detecting gross leaks and is widely used in food, medical, and consumer packaging.

Related reading:

• Bubble leak testing ASTM D3078 mistakes
• How to perform a bubble leak test

Gross Leak Detection by Internal Pressurization (ASTM F2096)

For pharmaceutical and medical packaging, ASTM F2096 provides a more sensitive approach to gross leak detection.

This method pressurizes the package internally and detects escaping air through submerged testing. It allows for precise identification of channels, seal defects, and substrate holes — often with greater sensitivity than traditional bubble testing.

Learn more:

• ASTM F2096 gross leak testing
• ASTM F2096 testing for medical packaging

Altitude Simulation Testing (ASTM D6653)

Packages often experience extreme pressure changes during air transport. Altitude simulation testing replicates these conditions to evaluate whether seals can withstand ascent, descent, and sustained altitude exposure.

This testing method is especially valuable for:

• E-commerce packaging
• Medical devices
• Flexible packaging shipped by air

Related standard:

• ASTM D6653 altitude testing

Dry Chamber Leak Testing (ASTM D5094)

Dry chamber testing is performed without liquid and is ideal for packages containing liquids, such as bottles, sachets, or containers with threaded or lug-style closures.

When pressure is applied, leaks are identified by visible liquid escaping onto absorbent material inside the chamber. This approach helps avoid contamination and simplifies cleanup for liquid-filled packages.

How Seal Integrity Testing Fits into a Complete QA Program

Seal integrity testing should not exist in isolation. It works best when integrated into a broader packaging quality control strategy.

When combined with:

• Seal inspection
• Package leak detection
• Leak testing to prevent recalls

…it becomes a proactive system for protecting product integrity rather than reacting to failures after the fact.

Why FlexPak Focuses on Visual Leak Detection

At FlexPak, we design seal integrity testing solutions that don’t just confirm if a package leaks — but show exactly where it leaks.

Our patented visual leak detection systems support:

• Food packaging
• Pharmaceutical packaging
• Medical device packaging

By providing clear, repeatable results in under 30 seconds, our testing methods help QA teams make confident decisions without guesswork.

If you’re evaluating equipment options, our guides on choosing the right leak tester and leak detection equipment by package type can help you determine the best fit.

Final Takeaway

Seal integrity testing is one of the most important safeguards in modern packaging. It verifies that seals perform under real-world conditions, protects consumers, and prevents costly failures before they happen.

When implemented as part of a comprehensive package integrity program, seal integrity testing helps manufacturers ship products with confidence — knowing every seal is ready for the job.