A pallet of vacuum-sealed meat pouches leaves a processing plant in Nebraska at 6 AM. By noon, that shipment is sitting in a FedEx feeder aircraft climbing to 19,000 feet with no pressurized cargo hold. The atmospheric pressure outside the packages drops from about 14.7 psi at sea level to roughly 7 psi. Inside those pouches, the trapped air expands with nowhere to go. Seals that held perfectly on the production floor start to flex, stretch, and in some cases fail completely.
The product arrives at its destination looking fine on the outside, but marginal seals have already been stressed beyond their limits. Microscopic channels may have opened in the seal area, compromising package integrity in ways that won’t be obvious until weeks later. Nobody catches it until customer complaints roll in.
This scenario plays out more often than most QA teams realize. Industry analyses of air-shipped goods consistently show that pressure-related closure and seal failures account for a significant share of in-transit packaging problems, particularly in plastic and metal containers. Glass packaging is also affected, though at lower rates. The altitude test exists precisely to prevent these failures before they happen, yet it remains one of the most underutilized tools in package integrity programs.
What Happens to Packages at High Altitude
Understanding why packages fail at altitude requires a quick look at basic physics. At sea level, the atmosphere exerts about 14.7 pounds of pressure per square inch on everything around us, including the outside of your sealed packages. When that package travels upward, whether in an aircraft or over a mountain pass, the external pressure drops while the internal pressure stays the same.
At 10,000 feet, external pressure falls to approximately 10 psi. At 19,000 feet, the operating ceiling for many feeder aircraft, it drops to around 7 psi. This creates a pressure differential that pushes outward against seals, closures, and flexible packaging materials. Think of what happens to a bag of chips when you drive through the mountains. That same expansion force is acting on your product packaging, but with much higher stakes.
Flexible pouches and bags are particularly vulnerable because they can physically expand. Modified atmosphere packaging (MAP), which relies on precise gas mixtures inside the package, faces a double threat. The pressure differential can stress seals while simultaneously disrupting the protective gas balance that keeps products fresh. Medical device packaging and pharmaceutical containers face sterility risks from even the smallest breach.
The effects aren’t always obvious. A seal may survive altitude exposure without visibly bursting, but the stress can open microscopic channels in marginal seal areas that allow slow oxygen ingress or moisture penetration. Products that appear intact on arrival may already be compromised in ways that won’t become apparent until shelf-life testing fails or, worse, until the product reaches consumers.
What Is an Altitude Test and How Does It Work
An altitude test, defined by ASTM D6653, simulates the reduced atmospheric pressure packages experience during high-altitude transport. Rather than loading products onto an aircraft and hoping for the best, the test recreates those conditions in a controlled environment using a vacuum chamber.
Sealed packages are placed inside the chamber, and the surrounding pressure is gradually reduced to match conditions at a target altitude. As the chamber pressure drops, it mimics the reduced atmospheric pressure encountered during air freight or high-elevation ground transport. Any weaknesses in seals, closures, or packaging materials are revealed under controlled stress.
A typical ASTM D6653 procedure includes conditioning samples at specified temperatures, commonly around 23°C or 5.6°C. The pressure is then reduced at a controlled rate to simulate ascent. Once the target pressure is reached, it is held for 60 minutes to apply sustained stress to the package. Afterward, the chamber is returned to atmospheric pressure and packages are inspected for deformation, leakage, or seal failure.
The value of this test lies in its predictive power. A package that survives 60 minutes at simulated high-altitude conditions has demonstrated the ability to withstand real-world pressure changes. A package that fails provides actionable insight into seal integrity, material selection, or distribution risk before product ever leaves the facility.
FlexPak altitude simulation equipment allows QA teams to perform these tests in-house with precise pressure control and repeatable results, eliminating delays associated with third-party labs.
Which Packages Need Altitude Testing
Not every package requires altitude testing, but more package types benefit from it than many QA teams expect.
Products shipped by air freight are the most obvious candidates, especially those moving through feeder aircraft networks operated by FedEx, UPS, and USPS. These aircraft often operate with unpressurized or partially pressurized cargo holds, exposing packages to altitudes approaching 20,000 feet.
Ground transportation can introduce altitude exposure as well. Trucks crossing major mountain ranges routinely encounter elevations exceeding 10,000 feet. A shipment traveling from Los Angeles to Denver or from Seattle to Salt Lake City may experience pressure differentials comparable to those seen in air transport. Assuming ground shipping eliminates altitude risk is a common and costly mistake.
Flexible packaging is particularly susceptible. Lightweight materials that perform well on the production floor may expand significantly under reduced pressure, stressing seals. Vacuum-sealed products require special attention because the pressure differential interacts with the internal vacuum, placing complex loads on seal areas.
MAP packaging for fresh proteins, produce, and prepared foods also requires altitude validation. Seal stress or minor seal openings can allow oxygen ingress and protective gas loss, accelerating spoilage even if the package still appears intact.
Medical device and pharmaceutical packaging often require documented performance across distribution hazards. ISO 11607 for sterile medical device packaging requires performance qualification for distribution hazards, which frequently leads teams to include altitude simulation when air transport is part of the supply chain. Similarly, pharmaceutical container closure integrity programs often consider pressure differentials as part of overall risk assessment.
Liquid-filled packages face additional challenges. Expanding headspace gas combined with hydrostatic pressure from the liquid can stress closures from multiple directions. Any squeezable or flexible liquid package should be evaluated under altitude conditions during development.
Altitude Test vs. Other Leak Detection Methods
Altitude testing serves a different purpose than traditional leak detection methods.
| Test Method | What It Detects | ASTM Standard | Leak Type | Best For |
| Altitude Test | Seal and closure failures caused by pressure differential | ASTM D6653 | Transport-induced failures | Air freight, mountain transport, pressure-sensitive products |
| Bubble Emission Test | Gross leaks with visible bubble location | ASTM D3078 | Gross leaks | Flexible packaging, routine QA sampling |
| Dry Chamber Test | Gross liquid leaks without submersion | ASTM D5094 | Gross liquid leaks | Bottled liquids, filled pouches |
| Internal Pressurization | Gross leaks revealed by positive pressure | ASTM F2096 | Gross leaks (hundreds of microns) | Rigid containers, sterile barrier packaging |
Bubble emission testing remains a workhorse for flexible packaging QA because it shows exactly where leaks occur. Altitude testing complements it by applying real-world transport stress that may cause marginal seals to fail even if no leak is present under standard conditions.
For applications requiring higher sensitivity, deterministic methods such as vacuum decay, helium leak detection, or high-voltage leak detection may be used. These methods detect very small leaks but do not replicate the mechanical stress of transport. Altitude testing fills that gap.
Common Altitude Testing Mistakes (And How to Avoid Them)
Testing at the wrong altitude is one of the most common errors. Many teams default to 8,000 feet based on typical commercial aircraft pressurization, but feeder aircraft and mountain routes often expose packages to much higher elevations. Test conditions should reflect actual distribution routes.
Shortening the hold time is another mistake. ASTM D6653 recommends maintaining target pressure for 60 minutes because some failures take time to develop. Reducing hold time can mask real vulnerabilities.
Sample selection also matters. Testing only ideal samples ignores normal process variation. Including samples from startups, shift changes, and end-of-run conditions provides a more realistic picture of performance.
Temperature effects are often overlooked. Conditioning samples per the standard ensures results are meaningful and repeatable.
Finally, incomplete documentation limits long-term value. Recording observations beyond pass/fail results helps identify trends and supports continuous improvement.
When to Add Altitude Testing to Your QA Process
Altitude testing should be added when distribution routes change, when new packaging materials or formats are introduced, when seasonal air shipping increases, or when unexplained field failures occur. It is also a valuable tool during new product development, where failures are far less costly to address.
Getting Started with Altitude Simulation Testing
Altitude testing does not require a large laboratory or complex infrastructure. FlexPak altitude simulation systems provide controlled pressure reduction, stable hold periods, and repeatable results in a compact footprint.
Many teams begin with baseline testing of existing packages to understand current performance. From there, altitude testing can be integrated into routine QA alongside other package integrity methods.
The investment pays dividends in reduced product damage, fewer complaints, and greater confidence in distribution performance. When you know your packages can survive simulated high-altitude conditions, you ship with confidence regardless of how carriers route your products.
Frequently Asked Questions About Altitude Testing
What is an altitude test?
An altitude test simulates reduced atmospheric pressure experienced during air transport or high-elevation ground shipping to evaluate package integrity.
What altitude should I test at?
Test at altitudes that reflect actual distribution conditions. Feeder aircraft may require testing up to 19,000 feet. Mountain routes may warrant 10,000 to 12,000 feet.
How long should the altitude hold be?
ASTM D6653 recommends a 60-minute hold at target pressure to allow seal stress to develop.
Can altitude testing replace bubble emission testing?
No. Altitude testing applies transport stress, while bubble emission testing detects existing leaks and shows where they occur. Using both provides more complete coverage.
Ready to add altitude testing to your QA program? FlexPak provides altitude simulation equipment backed by 25 years of experience helping packaging teams protect their products. Contact our team to discuss the right setup for your package formats and distribution requirements.