Sealing performance testing (hermeticity testing) is a core quality-control process that verifies the ability of packaging, components, and enclosures to prevent the leakage of gases or liquids under specified conditions. By quantifying leak rates and seal integrity against recognized standards published by ISO, IEC, ASTM, and GB, manufacturers can avoid product contamination, performance degradation, and safety failures. This article explains the technical principles, sample types, test items, testing methods, and typical applications of sealing performance testing.
Technical Overview
Sealing performance testing, also referred to as hermeticity testing or airtightness testing, is a family of evaluation techniques used to determine whether a sealed product, package, or assembly can maintain an effective barrier against the unwanted exchange of gases, liquids, or particulates. The tests work by establishing a pressure differential across the seal—either by pressurizing the test specimen internally or by drawing a vacuum around it—and then monitoring for evidence of leakage, such as pressure decay, bubble formation, or the escape of a tracer gas.
Results are typically expressed as a leak rate (for example, in Pa·m³/s, mbar·L/s, or standard cubic centimeters per minute), as a pass/fail judgment against a specified acceptance criterion, or as an ingress protection (IP) rating defined in IEC 60529 and GB/T 4208. Sealing performance testing is distinguished from seal strength testing: the former detects through-leaks and gross defects, while the latter (for example, ASTM F88) measures the mechanical force required to peel a seal apart. Both are complementary parts of a complete package or component integrity program.
Common reference standards include GB/T 17344 and GB/T 15171 for package airtightness, ASTM F2338 for vacuum decay leak testing, ASTM D3078 for bubble emission testing of flexible packaging, ASTM F2096 for internal pressurization, ASTM E432 for the selection of leak testing methods, and IEC 60529 for ingress protection of electrical enclosures. Accredited third-party laboratories routinely perform these tests as part of design validation, incoming inspection, and routine quality control.
Testing Samples
Rigid Packaging Containers
Metal cans, glass and plastic bottles, aerosol containers, drums, pails, and closed-head steel containers are tested to confirm that seams, closures, and gaskets do not allow product loss or microbial ingress. Typical tests include internal pressure retention, vacuum retention, and bubble emission after pressurization or evacuation.
Flexible Packaging
Retort pouches, vacuum bags, laminate films, blister packs, and sterile barrier systems are evaluated for pinholes, channel leaks, and poorly fused seals. Vacuum decay and bubble emission methods are widely used, supported by dye penetration for defect localization. Sterile medical packaging is often evaluated together with the requirements of ISO 11607.
Industrial Components and Assemblies
Valves, pipe fittings, pressure vessels, fuel tanks, radiators, heat exchangers, pumps, and compressor housings are tested at rated pressures to verify weld, braze, and gasket integrity. Helium leak detection and pressure decay methods are common, with test sensitivity selected according to the service medium and the safety classification of the component.
Electrical and Electronic Products
Enclosures, connectors, cable glands, outdoor luminaires, sensors, and control cabinets are tested for air tightness and for resistance to dust and water ingress. Lithium-ion battery cells, modules, and packs are a fast-growing application: the hermeticity of the cell can, vent, and pack enclosure directly affects safety, service life, and waterproof rating.
Medical and Pharmaceutical Products
Injectable vials, prefilled syringes, ampoules, IV bags, and combination products require container closure integrity to guarantee sterility throughout their shelf life. Vacuum decay, helium leak, and high-voltage leak detection methods are used to detect micro-leaks down to the micron scale.
Testing Items
Depending on the product type and applicable standard, a sealing performance test program generally covers the following items:
- Gross leak detection for sealed packages and components (pass/fail)
- Quantitative leak rate determination (Pa·m³/s, mbar·L/s, sccm)
- Airtightness of transport packages under internal pressure or external vacuum
- Vacuum retention and pressure decay characteristics over a defined hold time
- Seal integrity after conditioning such as vibration, drop, or thermal cycling
- Resistance to dust and water ingress (IP5X/IP6X and IPX1 to IPX8 ratings per IEC 60529 / GB/T 4208)
- Water spray, jet, and immersion tightness for outdoor enclosures and luminaires
- Helium leak rate for high-hermeticity components such as battery cells, sensors, and sealed electronics
Testing Methods
Pressure Decay Method
The specimen is pressurized with dry air or nitrogen to a specified level, isolated from the supply, and monitored for a defined period. Any pressure drop indicates leakage through seals, seams, or material defects. Differential pressure transducers allow detection of very small leaks, and the method is well suited to automated 100 percent inline inspection of machined parts, housings, and battery packs.
Vacuum Decay Method
The sealed package is placed in a test chamber, and a vacuum is drawn around it. Package expansion forces internal gas out through any leak path, and the resulting chamber pressure rise is measured. ASTM F2338 describes this non-destructive technique, which is widely used for pharmaceutical packaging, sachets, and rigid containers with sealed lids.
Bubble Emission Test
The specimen is submerged in water or another suitable liquid and pressurized internally, or placed under external vacuum. A continuous stream of bubbles reveals the leak location. The method is described in ASTM D3078 and GB/T 17344 and is valued for its simplicity and defect localization, although it is generally destructive and best suited to detecting relatively large leaks.
Internal Pressurization (Inflation) Test
Described in ASTM F2096, this method inflates a package while it is submerged and detects leaks during gentle flexing, making it effective for finding defects in gussets, folds, and seals of pouches and large bags.
Helium Mass Spectrometry Leak Detection
Helium is used as a tracer gas, either filled into the part (sniffing or hood methods) or forced into it under pressure (bombing method for sealed devices). A mass spectrometer detects escaping helium with sensitivity down to approximately 1 × 10⁻⁹ Pa·m³/s or better. This is the reference method for high-hermeticity products such as hermetic electronic packages, vacuum devices, and lithium-ion battery cells.
Ingress Protection (IP) Water and Dust Tests
Enclosures are subjected to dust chambers (talcum powder, IP5X/IP6X), drip boxes, spray nozzles, jet nozzles, and immersion tanks in accordance with IEC 60529 and GB/T 4208 to assign IP codes. For building products, the air permeability of windows, doors, and curtain walls is evaluated under standards such as GB/T 7106.
Applications
Sealing performance testing supports product quality and regulatory compliance across a broad range of industries:
- Food and beverage: shelf-life assurance, modified-atmosphere packaging integrity, and prevention of spoilage and microbial ingress
- Pharmaceuticals and medical devices: container closure integrity, sterile barrier verification, and compliance with ISO 11607 and pharmacopoeial requirements
- Automotive: fuel system leak testing, EV battery pack waterproofing, lamp and connector sealing, and brake component integrity
- New energy: hermeticity of lithium-ion cell enclosures, busbar housings, energy storage cabinets, and hydrogen system components
- Electronics and telecommunications: IP-rated outdoor enclosures, underwater connectors, and sealed sensors for harsh environments
- Aerospace and instrumentation: fuel and pneumatic system tightness, hermetic relay and sensor packages, and vacuum component qualification
- Construction and HVAC: air tightness of windows, doors, curtain walls, ductwork, and pipeline systems
FAQ
What is sealing performance testing?
It is a set of test techniques that verify whether a sealed package, component, or enclosure can prevent the leakage of gases or liquids. Results are expressed as a leak rate, a pass/fail verdict, or an ingress protection rating.
Which method should be chosen for a specific product?
Method selection depends on the required sensitivity, the volume and material of the test object, whether the test must be non-destructive, and the production throughput. ASTM E432 provides guidance for selecting leak testing methods; for example, vacuum decay suits non-porous sealed packages, while helium mass spectrometry is preferred for micro-leak detection in hermetic electronics and battery cells.
What is the difference between sealing performance testing and IP testing?
Sealing performance testing measures leak tightness directly, usually through pressure or tracer-gas techniques. IP testing per IEC 60529 evaluates an enclosure's resistance to dust and water ingress under standardized conditions and results in an IP code. The two are complementary: an air-tight enclosure will generally achieve a high IP rating, but IP tests do not quantify a leak rate.
Is sealing performance testing destructive?
Some methods, such as pressure decay, vacuum decay, and helium testing, can be non-destructive and suitable for 100 percent inspection. Others, such as water immersion bubble tests and dye penetration, wet or contaminate the specimen and are therefore destructive or suitable only for statistical sampling.
How are test results judged?
Acceptance criteria are defined by product standards, design specifications, or client agreements. A specimen passes if the measured leak rate is below the specified limit, no continuous bubble stream is observed, the pressure decay remains within tolerance, or the enclosure meets the required IP classification after water and dust exposure.