On August 1, 2025, GB/T 15171-2025 "Test method for seal performance of packaging" was officially released and will be fully implemented on February 1, 2026, replacing the thirty-year-old GB/T 15171-1994 "Test method for seal performance of flexible packaging". The core change of the new standard is the expansion of its scope from flexible packaging only to flexible, semi-rigid, and rigid packaging of all categories, along with the introduction of the vacuum decay method, marking the transition of packaging integrity testing from "qualitative judgment" to a new stage that values both qualitative and quantitative approaches.
I. Underwater bubble method: a classic approach for intuitively locating leak points
The specimen is placed in a vacuum chamber filled with test water and evacuated to create a pressure difference between the interior and exterior of the specimen. The escape of gas from the specimen or the infiltration of water into the specimen is observed to determine seal performance. This method is applicable to seal performance testing of packaging where water does not significantly affect the outer layer of the packaging.
Compared with the 1994 version, three technical revisions have been made:
- Instrumentation: A transparent perforated press plate is added, installed on the sealing cover to immerse the specimen in water, replacing the fixture fixation method of the old version for more convenient operation.
- Test water: Relaxed from "distilled water" to "clean and transparent test water".
- Test procedure: A blank test is required before formal testing to eliminate interference from residual gas in the water.
For result determination, the specimen is considered qualified if no continuous bubbles are generated during vacuum evacuation and pressure holding, and no water infiltration is found upon opening (when applicable). An isolated single bubble is generally considered residual gas in the test water and is not regarded as a leak.
The underwater bubble method offers advantages such as simple equipment, intuitive operation, and accurate leak point location, but it relies on visual observation, has insufficient sensitivity for micron-level leaks, and can only provide qualitative conclusions.
II. Vacuum decay method: a technological upgrade for quantitative detection of micro-leaks
The specimen is placed in a test chamber and evacuated. A high-precision pressure sensor monitors changes in vacuum degree within the test chamber to determine seal performance. This method is applicable to seal performance testing of various non-vacuum packaging, including flexible and rigid packaging.
Test results are expressed as "vacuum decay rate" in Pa/s, calculated using the formula Q = (P1 - P2)/T. This method references ASTM F2338-24 and has been previously adopted by the domestic pharmaceutical industry standard YY/T 0681.18-2020.
Core advantages include non-destructive testing, quantitative output, high sensitivity (capable of detecting leak channels of 3μm and above, with some instruments reaching 1μm), and objective and efficient operation.
A packaging seal tester that supports both methods can cover the full range of scenarios from routine sampling inspection to micro-leak monitoring.
III. Instrument technical requirements
A seal tester conforming to the new standard must meet the following requirements:
- Vacuum range: 0 to -90kPa, meeting the negative pressure testing needs of most packaging.
- Pressure accuracy: Not less than ±0.1kPa, with a resolution of not less than 0.01kPa.
- Automatic constant pressure compensation: Prevents pressure decay during the pressure-holding stage from causing test failure.
- Data management: Test data must be automatically stored, fully traceable, and searchable. The pharmaceutical industry must also meet GMP requirements, including audit trails and multi-level permission management.
The standard configuration of the vacuum chamber is typically Φ270mm×210mm (H), with custom sizes available upon request.
IV. Selection strategy between the two methods
| Dimension |
Underwater Bubble Method |
Vacuum Decay Method |
| Result format |
Qualitative (leak/no leak) |
Quantitative (Pa/s) |
| Sensitivity |
Low, dependent on visual observation |
High, up to μm level |
| Test method |
Semi-destructive |
Non-destructive |
| Equipment cost |
Low |
Relatively high |
| Application scenarios |
Routine sampling inspection, gross leak screening |
High-value products, micro-leak monitoring |
V. Practical significance of standard implementation
GB/T 15171-2025, through the introduction of the vacuum decay method, effectively addresses the technical pain points of the old standard, such as insufficient quantification and strong subjectivity in test results. The implementation of the new standard will significantly improve the packaging quality control level in multiple fields including food, pharmaceuticals, and medical devices.
For relevant enterprises, assessing whether existing seal testers meet the requirements of the new standard and establishing testing procedures aligned with it are tasks that need to be completed before the official implementation date of February 1, 2026. Enterprises currently building new testing capabilities are advised to directly configure equipment that supports both methods, reserving room for future upgrades.
The standard update is not the end point. The core lies in selecting the appropriate method based on product characteristics and quality requirements, and establishing a scientific and effective packaging integrity testing system. Methods themselves do not become outdated; what matters is how and where they are applied.
