Your packages passed bubble emission testing on the production floor. Three days later, a customer in Denver reported leaking pouches from an air-shipped lot.
The seal wasn’t defective when it left the facility. It failed because the pressure differential during the flight stressed a marginal seal that was already near its failure limit — and that weakness was invisible under standard production floor testing conditions. That’s exactly what ASTM D6653 altitude simulation is designed to catch before the shipment goes out.
This guide covers what D6653 actually does, which products and shipping routes warrant it, how to run it correctly, and how to pair it with a detection method so your results are actionable.
In this article:
- What Is ASTM D6653?
- What Altitude Does to a Sealed Package
- Which Products and Shipping Routes Need This Test
- How to Run an ASTM D6653 Test Correctly
- Altitude Simulation Vacuum Settings Reference Chart
- Running Altitude Simulation on a FlexPak Unit
- Frequently Asked Questions
What Is ASTM D6653?
ASTM D6653 is a conditioning test method that simulates the pressure differential packaging experiences during air shipment or high-altitude ground transport. It is not a leak detection method — it stresses the package under reduced pressure to reveal existing seal weaknesses, and must be paired with a detection method such as ASTM D3078 bubble emission testing afterward to identify any leaks the conditioning step exposed.
That distinction matters more than it might seem. Running D6653 alone and observing no visible damage tells you almost nothing about seal integrity. The pressure differential during altitude simulation can open microscopic channels in marginal seals that were already near their failure limit — channels that may not be visible but will allow gas exchange, moisture ingress, or product contamination during distribution. The detection step is what makes those failures visible.
D6653 results are qualitative: they indicate whether a package was affected by simulated altitude conditions, not by how much. Paired with D3078, the combination tells you whether your packaging can survive the shipping environment it will actually face.
What Altitude Does to a Sealed Package
At altitude, atmospheric pressure drops. For a sealed package with internal headspace gas, that drop creates an outward pressure differential — the internal pressure is now higher relative to the surrounding environment, which pushes against seal areas and package film from the inside.
For a well-sealed package with a strong, uniform seal, this outward pressure is handled without issue. For a package with a marginal seal — one that passed visual inspection and standard bubble testing but has a minor inconsistency in seal bar pressure, dwell time, or temperature — the altitude differential can open a microscopic channel that was already near its failure limit.
Here’s the critical distinction: altitude simulation reveals these weaknesses. It does not create them. The defect was present before the test. D6653 simply applies the real-world stress that exposes it — the same stress the package would encounter on a flight or a mountain highway route. A package that fails altitude simulation was always going to fail in transit. Finding that out in the test chamber is the point.
This is also why altitude testing pairs naturally with cold-chain programs. Refrigerated and frozen shipments experience both the pressure differential of air transport and the added stress of low-temperature materials that are less flexible and more brittle under pressure. The ASTM D6653 standard calls for specimens to be conditioned to around 42°F before testing when simulating cold-chain shipping environments — a detail that’s easy to overlook but matters significantly for meat, dairy, and pharmaceutical cold-chain packaging.
Which Products and Shipping Routes Need This Test
Not every product or shipping route warrants altitude simulation. The question is whether the pressure differential your packaging will experience during distribution is large enough to stress marginal seals beyond their tolerance.
Air freight creates the largest pressure differentials. Pressurized cargo jets are typically pressurized to around 8,000 feet equivalent — meaning the package experiences a pressure differential corresponding to roughly 8,000 feet of altitude even in a controlled hold. Nonpressurized feeder aircraft used for regional delivery routes typically reach around 13,000–16,000 feet, with field data showing some routes reaching as high as around 19,700 feet. If your product moves through any air freight network, altitude simulation is worth including in your validation program.
High-altitude ground transport matters too — and it’s often overlooked. Ground transport over mountain passes in regions like the Rocky Mountains, the Andes, or the Alps can expose packages to altitudes of around 10,000–12,000 feet. For packaging with tight seal tolerances or modified atmosphere requirements, that differential is meaningful.
Products most likely to benefit from D6653 testing:
- Flexible food pouches and bags with modified atmosphere packaging (MAP)
- Pharmaceutical packaging where headspace gas composition affects product stability
- Medical device packaging with sterile barrier requirements
- Any package where a seal failure during transit would compromise safety or shelf life
For products shipping exclusively by ground at low elevation with generous seal strength margins, standard bubble emission testing under D3078 may be sufficient. If you’re unsure whether your distribution environment warrants altitude simulation, the package leak detection buyer’s guide covers method selection by shipping format and risk level.
Cold-chain shippers should also consider the cold-chain packaging integrity guide for specific guidance on specimen conditioning and paired testing protocols.
How to Run an ASTM D6653 Test Correctly
The procedure has three phases: specimen preparation, altitude simulation, and post-conditioning detection. The detection phase is not optional — D6653 without a paired detection method produces no actionable result.
Equipment needed:
- Vacuum chamber capable of reaching the target altitude equivalent vacuum level
- Vacuum pump and calibrated pressure gauge
- Temperature-controlled environment or refrigerator for cold-chain specimen conditioning (target ~42°F for cold-chain)
- Detection method equipment (FlexPak Leak Detector for D3078 pairing)
Step 1 — Prepare specimens. Select at least three production specimens per lot. If testing cold-chain packaging, condition specimens to around 42°F before beginning the altitude simulation phase. This reflects the actual temperature of the packaging when it enters the air freight environment and produces more representative results.
Step 2 — Set altitude simulation parameters. Using the vacuum gauge setpoint chart (see section below), identify the vacuum level that corresponds to your target simulated altitude. Set ascent rate to between 300 and 5,000 feet per minute — the rate at which vacuum is drawn should reflect realistic aircraft climb rates, not an abrupt pull to maximum vacuum. Set your hold time at maximum simulated altitude based on your expected flight duration or worst-case route.
Step 3 — Run the altitude simulation. Place specimens in the vacuum chamber. Apply vacuum at the validated ascent rate to reach the target setpoint. Hold at maximum simulated altitude for the specified duration. Depressurize at the validated descent rate — gradual depressurization reflects real descent conditions and prevents abrupt pressure reversal that isn’t representative of actual transport.
Step 4 — Run the detection test immediately. Transfer conditioned specimens directly to the bubble emission test (ASTM D3078) without delay. The D6653 conditioning step stresses the package — the D3078 step is what reveals whether any seal failures resulted from that stress. Run the bubble test per your validated D3078 protocol. A continuous bubble stream from a post-conditioning specimen indicates a seal that could not withstand the altitude differential it will face in distribution.
Step 5 — Document both phases. Record altitude setpoint, ascent/descent rates, hold time, specimen conditioning temperature, D3078 vacuum level, hold time, and results. Both phases of the test need to be documented together — they’re one test protocol, not two separate tests.
For a detailed walkthrough of the D3078 detection step, see the bubble leak test procedure guide.
Altitude Simulation Vacuum Settings Reference Chart
The FlexPak Leak Detector’s vacuum gauge must reach the corresponding setpoint to simulate the target altitude pressure. Always subtract your Facility Vacuum Offset (FVO) when setting vacuum targets — the FVO accounts for the difference between your facility’s elevation and sea level, and skipping this step means your simulated altitude is off by your facility’s actual elevation.
Imperial (feet / inHg)
| Altitude (ft) | Absolute Atmospheric Pressure (inHg) | Vacuum Gauge Setpoint (inHg) |
|---|---|---|
| 0 | 29.9 | 0 |
| 1,000 | 28.9 | 1.0 |
| 2,000 | 27.8 | 2.1 |
| 4,000 | 25.8 | 4.1 |
| 6,000 | 24.0 | 5.9 |
| 8,000 | 22.2 | 7.7 |
| 10,000 | 20.6 | 9.3 |
| 15,000 | 16.9 | 13.0 |
| 20,000 | 13.8 | 16.1 |
| 30,000 | 8.89 | 21.0 |
| 40,000 | 5.52 | 24.4 |
Metric (meters / kPa)
| Altitude (m) | Absolute Atmospheric Pressure (kPa) | Vacuum Gauge Setpoint (kPa) |
|---|---|---|
| 0 | 101 | 0.0 |
| 305 | 97.7 | 3.3 |
| 610 | 94.2 | 6.8 |
| 1,219 | 87.5 | 13.5 |
| 1,829 | 81.2 | 19.8 |
| 2,438 | 75.3 | 25.7 |
| 3,048 | 69.7 | 31.3 |
| 4,572 | 57.2 | 43.8 |
| 6,096 | 46.6 | 54.4 |
| 9,144 | 30.1 | 70.9 |
| 12,192 | 18.7 | 82.3 |
Values derived from ASTM D6653. The vacuum gauge setpoint represents the differential pressure between sea level and the target altitude — not an absolute pressure reading. Always apply your Facility Vacuum Offset before setting targets.
For most North American air freight programs, a setpoint corresponding to around 8,000 feet is a commonly used starting point for pressurized cargo holds. For nonpressurized feeder aircraft routes, setpoints corresponding to around 13,000–16,000 feet are more representative. Your validated protocol may specify differently based on your actual distribution network.
Running Altitude Simulation on a FlexPak Unit
FlexPak Leak Detectors support both ASTM D6653 altitude simulation and ASTM D3078 bubble emission testing in a single unit — no reconfiguration required between the conditioning and detection phases.
The FPSA-T touchscreen controller includes a dedicated Altitude Test mode with separate recipe storage for altitude simulation parameters (altitude setpoint, ascent rate, descent rate, hold time at maximum altitude) and bubble emission parameters (vacuum level, hold time). The 1+2 Run function runs both tests in sequence automatically — the unit completes the altitude simulation phase, then immediately transitions to the bubble emission detection phase. That means the two-test protocol described above can run as a single programmed sequence, reducing setup time and eliminating the risk of delay between conditioning and detection.
Up to 26 altitude simulation recipes can be stored alongside 24 bubble emission recipes, supporting QA programs that test multiple SKUs or shipping routes without re-entering parameters each time. The data acquisition and logging function records both phases together in a single test record — which is what auditors and customers want to see when they ask for altitude simulation validation documentation.
Ready to add altitude simulation to your testing program? See the FlexPak altitude simulation page for equipment details, or get a quote configured for your package formats and shipping routes.
Frequently Asked Questions
Does ASTM D6653 detect leaks?
No. ASTM D6653 is a conditioning method, not a detection method. It simulates the pressure differential packaging experiences during air shipment or high-altitude ground transport, stressing the package under reduced pressure. To determine whether any seal failures resulted from the conditioning step, D6653 must be paired with a detection method — typically ASTM D3078 bubble emission testing — run immediately after the altitude simulation is complete.
What vacuum level should I use for altitude simulation testing?
The correct vacuum setpoint depends on the shipping route you’re simulating. Pressurized cargo holds are typically equivalent to around 8,000 feet, corresponding to a vacuum gauge setpoint of around 7.7 inHg (or 33.6 kPa). Nonpressurized feeder aircraft routes typically reach around 13,000–16,000 feet. Use the altitude simulation chart in this guide to identify the setpoint for your target altitude, then subtract your Facility Vacuum Offset to account for your facility’s elevation.
Do I need altitude simulation testing if I only ship by ground?
Possibly. Ground transport over high-altitude routes — mountain passes in regions like the Rockies or the Alps — can expose packages to altitudes of around 10,000–12,000 feet. If your distribution network includes these routes and your packaging has tight seal tolerances or modified atmosphere requirements, altitude simulation is worth including in your validation program. For low-elevation ground-only distribution with robust seal margins, standard D3078 bubble emission testing may be sufficient.
How does ASTM D6653 relate to ASTM D3078?
D6653 and D3078 are complementary methods designed to be used together. D6653 is the conditioning step — it simulates altitude pressure to stress the package. D3078 is the detection step — it reveals whether the conditioning step exposed any seal failures. Running D6653 without a paired detection method like D3078 produces no actionable leak detection result. For a full walkthrough of the D3078 procedure, see the bubble leak test guide. For a broader view of how both methods fit within container closure integrity testing, see the CCIT overview.