Your seals passed every test on the production floor. The bubble test showed no leaks. Quality control signed off. Then the complaints started rolling in from customers on the West Coast, and suddenly you’re staring at photos of pouches that look like they exploded from the inside. The seals didn’t fail because they were weak. They failed because you tested them at sea level, and your product flew at 35,000 feet. This is precisely the scenario that ASTM D6653 was designed to prevent, and understanding this standard could be the difference between confident shipments and costly customer complaints.
The reality is that most QA teams don’t think about altitude until it becomes a problem. And by then, the damage is done. Products arrive compromised, customers lose trust, and the finger-pointing begins. Was it the sealing equipment? The film supplier? The warehouse conditions? More often than not, the answer is simpler and more frustrating: nobody tested for altitude.
What Is ASTM D6653 and When Does It Apply
ASTM D6653 is a test method that determines how pressure changes at high altitude affect packaging systems. The official title is “Standard Test Methods for Determining the Effects of High Altitude on Packaging Systems by Vacuum Method,” which sounds complicated until you understand what it actually does. The test places your package inside a vacuum chamber and gradually reduces the pressure to simulate what happens when that package travels on a cargo plane or gets trucked over a mountain pass.
Here’s why this matters more than most people realize. According to the ASTM D6653 standard documentation, packaged products transported via feeder aircraft networks can experience altitudes as high as 19,000 feet. At that elevation, the external air pressure drops significantly while the pressure inside your sealed package stays exactly where it was when you sealed it on the production floor. That pressure differential creates stress on your seals that ground-level testing simply cannot replicate.
When does ASTM D6653 apply to your operation?
The standard applies whenever your products face significant pressure changes during distribution. This includes air freight shipments, which is obvious, but it also covers ground transportation over mountain passes in regions like Colorado, the Sierra Nevada, or anywhere with elevation changes exceeding 4,000 feet. If your snack bags end up in Denver retail stores, your pet food ships to distributors in Salt Lake City, or your pharmaceutical products fly overnight across the country, altitude simulation testing should be part of your QA protocol.
The test also comes into play during packaging development and engineering phases. Rather than waiting for field failures to identify seal weaknesses, proactive QA teams use ASTM D6653 to validate new package designs before they ever hit production. This approach catches problems early when fixes are cheap and reputations are intact.
How Altitude Affects Flexible Package Seals
The physics behind altitude-related seal failures is straightforward once you see it in action. When you seal a flexible package at your facility, you’re trapping air inside at whatever atmospheric pressure exists at your location. For most production facilities in the United States, that’s somewhere around 14.7 PSI at sea level or slightly less at higher elevations.
Now imagine that sealed package loaded onto a cargo plane. As the aircraft climbs, the external pressure drops. The air inside your package doesn’t know this is happening. It maintains its original pressure, which means the pressure differential between inside and outside keeps growing as altitude increases. Your package starts to inflate like a balloon because the internal pressure is now greater than the pressure pushing back from outside.
This inflation puts tremendous stress on your seals. For flexible packaging with heat seals, this stress concentrates at the weakest points of the seal line. Micro-channels that passed bubble testing at ground level can open up under altitude pressure. Seals that seemed perfectly adequate now stretch, deform, and eventually breach.
What makes this particularly frustrating for QA managers is the intermittent nature of the failures. Not every package fails. Some survive because they happened to have slightly stronger seals. Others fail spectacularly. The inconsistency makes root cause analysis difficult and often leads teams down the wrong path investigating equipment issues or operator error when the real culprit was altitude exposure all along.
Research from Clemson University’s packaging program has explored the relationship between seal strength and pressure differentials in flexible pouches. The findings confirm what field experience suggests: seals that pass peel strength tests can still fail burst tests under pressure because the failure mechanisms are different. A seal might have adequate strength to resist pulling apart but insufficient integrity to withstand internal pressurization from all directions simultaneously.
Who Needs Altitude Simulation Testing
The short answer is anyone shipping flexible packaging by air or over mountainous terrain, but the practical answer requires more nuance. Some industries face higher stakes than others, and some distribution patterns create more exposure than others.
Food manufacturers shipping snacks, chips, and puffed products sit at the top of the risk list. These packages already contain trapped air as part of their protective cushioning for the product. That air expands at altitude, and the result is often dramatic package bulging or outright bursting. Major snack brands have learned this lesson and now require altitude simulation testing as part of their supplier qualification process. If you’re a co-packer producing for national brands, expect ASTM D6653 compliance to show up in your customer audits.
Meat and seafood processors using modified atmosphere packaging face similar challenges. The gas flush that extends shelf life becomes a liability at altitude if seals can’t contain the expanding atmosphere. A single leak compromises the entire value proposition of MAP packaging, and altitude-induced failures often don’t become apparent until the product is already in the retail case showing signs of premature spoilage.
Pet food manufacturers shipping to distribution centers across varying elevations encounter altitude effects regularly. The kibble itself doesn’t care about pressure changes, but the packaging certainly does. Odor leaks from failed seals trigger customer complaints even when the product inside remains technically safe to use. Brand perception takes a hit that no amount of quality product can fully recover.
Medical and pharmaceutical packaging operates under even stricter requirements. Sterile barrier systems that breach at altitude compromise patient safety, and the regulatory implications of such failures extend far beyond product replacement costs. The FDA and international regulatory bodies expect manufacturers to demonstrate that packaging maintains integrity throughout the distribution environment, and altitude exposure is explicitly part of that environment for air-shipped products.
The comparison below highlights which testing approach fits different operational scenarios:
| Scenario | Primary Test Method | When to Add ASTM D6653 |
| Local distribution only, no elevation changes | ASTM D3078 (bubble emission) | Not typically required |
| Regional distribution including mountain states | ASTM D3078 + D6653 | Always recommended |
| National distribution via ground freight | ASTM D3078 + D6653 | If routes cross elevations above 4,000 ft |
| Air freight shipping (any distance) | ASTM D3078 + D6653 | Always required |
| Export to international markets | ASTM D3078 + D6653 | Required for air freight, recommended otherwise |
| Medical/pharma with sterile claims | ASTM D6653 + F2096 | Required as part of package validation |
How to Run an ASTM D6653 Test Step by Step
Running an ASTM D6653 test requires the right equipment and a methodical approach. The standard provides flexibility in test parameters to match real-world distribution conditions, but the core procedure remains consistent.
Step 1: Prepare your test specimens. Select packages that represent actual production conditions, not hand-made samples or carefully prepared specimens that don’t reflect what comes off your sealing equipment day to day. The standard recommends testing a minimum of three specimens to generate meaningful data, though many QA programs test larger sample sizes for statistical confidence. Condition the packages at 23°C ± 2°C for at least 24 hours before testing if your facility cannot maintain consistent conditions.
Step 2: Set up the vacuum chamber. Your chamber needs to accommodate the test specimens with extra room for expansion during the test. This is important because packages will inflate as pressure drops, and a chamber that’s too small will produce inaccurate results or potentially damage the specimens before they reach target altitude. Verify that your vacuum gauge reads accurately across the 0 to 100 kPa range and that all valves operate smoothly.
Step 3: Establish your target altitude and ramp rate. The standard recommends increasing vacuum at approximately 1,000 feet (about 300 mbar) every 30 to 60 seconds until you reach your target altitude. For products shipped via feeder aircraft, 19,000 feet represents the maximum expected exposure. For ground freight over mountain passes, 14,000 feet covers most North American routes. Choose parameters based on your actual distribution environment rather than defaulting to maximum values that don’t reflect reality.
Step 4: Hold at target altitude. Once you reach the target pressure, maintain it for 60 minutes. This duration allows time for any latent seal weaknesses to manifest. Some seal failures occur immediately upon reaching altitude, while others develop gradually as materials creep under sustained stress. The 60-minute hold captures both failure modes.
Step 5: Observe and document results. Watch for bulging, distortion, audible leaks, or visible seal separation during the test. After the hold period, gradually return the chamber to atmospheric pressure and remove specimens for inspection. Document any permanent deformation, seal channel opening, or product contamination that occurred during the test. Photographs of failed specimens provide valuable reference for troubleshooting and process improvement.
What does a passing result look like?
A package passes ASTM D6653 when it maintains seal integrity throughout the altitude simulation without leakage, permanent deformation that compromises function, or structural failures that affect product protection. The standard emphasizes qualitative assessment, meaning there’s no single numerical threshold that defines pass or fail. Instead, you evaluate whether the package would still protect the product adequately after experiencing the simulated distribution conditions.
Common Mistakes That Skew Altitude Test Results
Even experienced QA teams make errors that compromise the validity of their altitude simulation testing. Understanding these pitfalls helps you generate data you can actually trust.
Testing non-representative samples tops the list of common mistakes. It’s tempting to pull packages specifically for testing that look particularly good or that came from a well-monitored production run. The problem is that these samples don’t represent your actual output. Real-world failures come from the packages that slipped through with marginally acceptable seals, not from your best work. Random sampling from normal production provides data that actually predicts field performance.
Using incorrect altitude parameters creates false confidence. If your products ship to Albuquerque but you test at 5,000 feet because that’s what someone set the chamber to years ago, you’re missing the 6,000+ feet of elevation that Albuquerque actually sits at, plus any additional altitude from the truck route getting there. Map your distribution network and test to the highest elevation your products realistically encounter.
Rushing the pressure ramp causes seal failures that wouldn’t occur in actual transport conditions. Aircraft don’t climb from sea level to cruising altitude in 30 seconds. When you increase vacuum too quickly, you create shock loading on seals that exceeds what they’d experience in real distribution. Follow the 30 to 60 second per 1,000 feet guideline unless you have specific data suggesting your products experience faster pressure changes.
Skipping the hold time misses slow-developing failures. Some seal weaknesses only manifest after sustained pressure exposure as materials relax and micro-channels open up. If you reach target altitude and immediately begin depressurization, you might pass packages that would fail in actual flight conditions where they spend hours at reduced pressure.
Failing to document environmental conditions makes troubleshooting impossible later. Temperature and humidity both affect seal performance, and if you don’t record conditions during testing, you can’t correlate test results with potential seasonal variations in field failures. Consistent documentation turns individual tests into trend data that actually improves your process.
Choosing the Right Equipment for ASTM D6653
Altitude simulation testing equipment ranges from basic manual chambers to fully automated systems with programmable profiles and digital data logging. The right choice depends on your testing volume, documentation requirements, and integration with other package integrity tests.
At minimum, you need a vacuum chamber capable of withstanding approximately one atmosphere of pressure differential, a vacuum gauge with appropriate range and accuracy, and inlet and outlet tubes with manual valves for controlling the pressure ramp. The chamber must be sized to accommodate your largest package format with room for expansion during testing. Transparent chambers allow visual observation during the test, which helps identify exactly when and where failures occur.
For higher-volume operations or those with strict documentation requirements, automated systems offer significant advantages. Programmable altitude profiles ensure consistent test conditions across operators and shifts. Digital data logging creates records that satisfy auditor expectations and enable statistical process control. Some systems integrate altitude simulation with bubble emission testing, allowing you to check for seal breaches at altitude by filling the chamber with water and watching for bubbles under vacuum conditions.
What detection sensitivity should you expect?
Altitude simulation testing per ASTM D6653 can detect leak paths down to approximately 250 microns when combined with visual observation or bubble emission methods. This sensitivity level catches gross leaks and significant seal failures but may miss very small defects that only cause problems over extended storage periods. For applications requiring higher sensitivity, consider supplementing ASTM D6653 with ASTM F2338 testing, which can detect defects down to 50 microns.
The decision between in-house testing and external lab services depends on your volume and expertise. External labs offer calibrated equipment, experienced operators, and certifications that carry weight with customers and auditors. In-house testing provides faster turnaround, lower per-test costs at volume, and the ability to test during production rather than waiting for scheduled lab appointments. Many operations use both: in-house testing for routine monitoring and external labs for validation studies and customer qualification requirements.
FlexPak altitude simulation equipment brings this testing capability directly to your plant floor, eliminating the delays and logistics of sending samples to external facilities. When you can test during production, you catch problems before product ships rather than learning about them from customer complaints weeks later.
Ready to stop guessing whether your seals will survive shipping?
If altitude-related failures have cost you customers, caused complaints, or simply kept you up at night wondering what’s happening to your products in transit, it’s time to add ASTM D6653 testing to your QA program. Get a response within 24 hours on equipment that fits your package formats and testing requirements. Your seals work hard on the ground. Make sure they work just as hard at 19,000 feet.