A single pinhole leak—smaller than a grain of sand—can trigger a recall that costs your company millions and damages customer trust for years. The challenge isn’t whether you need a leak tester. It’s knowing which one actually catches the leaks that matter for YOUR packages, before they ship.
Whether you’re packaging fresh proteins, pharmaceuticals, or snack foods, choosing the wrong leak testing method means either missing critical defects or wasting time and money on equipment that doesn’t fit your needs. This guide breaks down exactly what each type of leak tester does, which packages it works for, and how to match the right testing method to your production—so you can protect your products and your reputation.
What Does a Leak Tester Actually Do?
A leak tester detects holes, seal failures, and micro-cracks in packaging using methods like bubble emission, pressure change, or altitude simulation. For flexible packaging, detection sensitivity typically reaches approximately 250 microns—about the width of two human hairs—identifying defects that cause spoilage, contamination, or recalls before products leave your facility.
Unlike industrial leak testing used in automotive or HVAC applications, packaging leak testers focus specifically on seal integrity. They answer two critical questions:
- Is there a leak? — Pass/fail determination for quality control
- Where is the leak? — Pinpointing the exact defect location for process improvement
The best leak testers for packaging don’t just tell you IF there’s a problem. They show you WHERE that problem is, so you can trace it back to the sealing equipment, operator error, or material defect causing it.
Most flexible packaging applications use ASTM-compliant test methods, which provide standardized, repeatable procedures that satisfy auditor requirements and customer specifications. The four main methods each work differently—and each fits different package types.
4 Leak Testing Methods for Packaging Explained
1. Bubble Emission Testing (ASTM D3078)
How it works: Submerge the package in water inside a vacuum chamber. As the chamber pressure drops, air escapes from any leak points—and you watch bubbles form at the exact defect location.
Detection sensitivity: Approximately 250 microns (practical limit under typical test conditions)
Test time: 30 seconds or less
Best for: Flexible pouches, bags, sachets, stick packs, and most food packaging
Why it matters: Bubble emission is the most widely used method for flexible packaging because it’s visual, fast, and shows you exactly where the leak is. When bubbles stream from a corner seal, you know immediately that your sealing equipment needs attention at that station.
2. Altitude Simulation Testing (ASTM D6653)
How it works: Recreate the pressure changes packages experience during air transport or shipping over mountain passes. The test chamber simulates altitudes up to 14,000 feet, stressing seals to reveal weaknesses.
Detection sensitivity: 250 microns
Best for: Packages shipped by air, products distributed across varying elevations, snack bags and chip packaging
Why it matters: A seal that holds at sea level may fail when pressure drops during a flight to Denver. Altitude simulation catches these failures before your customer opens a bag of crushed, stale chips.
3. Dry Chamber Testing
How it works: Similar to bubble emission, but designed for liquid-filled packages. The package sits in a dry chamber on absorbent material while pressure changes force any leaking liquid to become visible—without submerging your product in water.
Detection sensitivity: Approximately 250 microns
Best for: Liquid dairy pouches, sauce packets, beverage pouches, any liquid-filled flexible package
Why it matters: You can’t dunk a milk pouch in water and then sell it. Dry chamber testing gives you bubble emission-level detection without contaminating or damaging your product.
4. Internal Pressurization Testing (ASTM F2096)
How it works: Instead of pulling a vacuum around the package, you pressurize FROM WITHIN. Air is injected into the package, and any leaks allow that air to escape—detected either visually (bubbles when submerged) or through pressure decay measurement.
Detection sensitivity: 250 microns (bubble method) or higher with pressure decay
Best for: Medical device packaging, pharmaceutical blister packs, sterile barrier systems
Why it matters: Medical and pharma packaging requires documentation that seals meet specific integrity standards. Internal pressurization supports compliance with ISO 11607 and USP <1207> while giving QA teams a daily-use tool for batch testing.
Which Leak Tester Fits Your Package Type?
Here’s the decision framework most leak tester guides don’t give you. Match your package type to the right method:
| Package Type | Recommended Test Method | ASTM Standard | Detection Sensitivity |
| Flexible pouches (food) | Bubble Emission | D3078 | 250 microns |
| Vacuum-sealed meat/cheese | Bubble Emission + VAC attachment* | D3078 | 250 microns |
| Stick packs & sachets | Bubble Emission | D3078 | 250 microns |
| Liquid-filled pouches | Dry Chamber | — | ~250 microns |
| Snacks shipped by air | Altitude Simulation | D6653 | 250 microns |
| Medical/sterile packaging | Internal Pressurization | F2096 | 250 microns |
| Pharma blister packs | Internal Pressurization or High-Sensitivity | F2096 or F2338 | 250 or 50 microns |
*Vacuum-sealed packages can be tested via ASTM D3078 bubble emission—they just need to be inflated with air prior to testing using a VAC attachment.
The key insight: Most flexible food packaging works with bubble emission testing (ASTM D3078). It’s the most versatile, most visual, and fastest method for everyday QA. You only need specialized methods when your package type demands it—liquid contents, altitude exposure, or sterile barrier requirements.
ASTM Standards for Leak Testing: What You Need to Know
ASTM standards aren’t just bureaucratic checkboxes. They’re your proof that testing was done correctly, consistently, and in a way that auditors, customers, and regulators recognize.
Here’s what each standard actually means for your operation:
ASTM D3078 — The bubble test. Tells you if there’s a leak AND shows you where. The workhorse standard for flexible food packaging. Detection typically down to approximately 250 microns.
ASTM F2096 — Internal pressurization for medical and pharma seals. Required for sterile barrier validation. Supports compliance with ISO 11607.
ASTM D6653 — Altitude simulation. Tests how seals perform under shipping pressure changes. Essential if your products fly or cross mountain ranges.
Dry Chamber Testing — A variation of bubble emission for liquid-filled packages. Same detection capability, but keeps liquid products dry and sellable.
ASTM F2338 — Vacuum decay testing reaching single-micron sensitivity. Used when standard 250-micron detection isn’t tight enough for your application—typically pharma and medical devices requiring deterministic test methods per USP <1207>.
When a customer or auditor asks “How do you test package integrity?”, citing the specific ASTM standard gives them confidence that your QA process follows recognized, repeatable methodology. Learn more about ASTM testing methods.
5 Questions to Ask Before Buying a Leak Tester
Not all leak testers work for all applications. Before you invest, get clear answers to these questions:
1. What package types will you test? Flexible pouches, rigid trays, vacuum-sealed bags, and liquid-filled sachets each have optimal test methods. A leak tester built for rigid containers won’t help with flexible film pouches. See compatible package types.
2. Do you need to test vacuum-sealed packages? Standard bubble emission requires air inside the package. If you’re testing vacuum-sealed products, you need a VAC attachment that inflates packages before testing—or you’ll get no results.
3. Which ASTM standard does your customer or industry require? Food manufacturers typically need ASTM D3078. Medical device companies often require F2096 and ISO 11607 documentation. Know your requirement before you buy.
4. How fast do you need results? Bubble emission delivers results in 30 seconds or less. If you’re testing hundreds of packages per shift, cycle time matters. Some methods take longer—make sure the equipment matches your production pace.
5. Do you need to see WHERE the leak is, or just IF there’s a leak? Pressure decay methods tell you pass/fail. Bubble emission shows you the exact location. If you’re troubleshooting seal quality issues, visual confirmation saves hours of guesswork.
Your Next Step: Finding the Right Fit
Choosing a leak tester isn’t about finding the most expensive equipment or the most features. It’s about matching the right method to YOUR packages, YOUR industry requirements, and YOUR production needs.
The fastest path to the right answer? Share your package dimensions and testing requirements with a specialist who’s helped thousands of manufacturers solve this exact problem.
Step 1: Tell us what you’re packaging and what industry you’re in. Step 2: We recommend the ideal unit and any add-ons (like VAC attachments for vacuum-sealed products). Step 3: You get results in 30 seconds or less—with the confidence that comes from ASTM-compliant testing.
Ready to protect your products? See Which Unit Fits Your Package →
FlexPak has helped food, pharmaceutical, and medical device manufacturers prevent leaks for over 25 years. Our team responds within 24 hours with personalized recommendations based on your specific package type and testing needs.