Hermetic Sealing: Reliable Protection Against Contamination and Unwanted Substance Leakage
Last updated: 14. April 2026
Hermetic sealing of packaging or components creates a gas-tight encapsulation and thus prevents material exchange(especially of gases). It is not to be equated with IP protection ratings (dust/water); the required degree of tightness is defined on an application-specific basis via permissible leak rates and is verified and validated using suitable procedures (e.g., helium leak testing). Depending on the area of application (e.g., protection against microbes, moisture, dust, or chemical influences, or the avoidance of leakage/evaporation), proven processes and designs are used that demonstrably achieve the required integrity.
Types of hermetic sealing in various fields of application
In general, hermetic sealing is used in the following areas:
- Food industry
- Electronics
- Industrial plants and mechanical engineering
- Technology and electrical engineering
In every field, hermetic sealing ensures the sterility of products.
Compliance with regulatory requirements
In the case of hermetic sealing, the legal requirements and technical standards applicable to the respective field of application and target market must be strictly observed. Depending on the industry and intended use, the sealing process is subject to specific quality assurance standards and official regulations.
These guidelines serve to ensure seamless compliance with defined quality criteria. They form the basis for product safety, functionality under extreme conditions, and the protection of end consumers.
Methods of hermetic sealing
Depending on which products or technical components need to be protected, different processes for hermetic sealing are available. The most common methods are:
- Welding
- Soldering
- Bonding with resins
- Sealing with glass-to-metal or ceramic-to-metal
Sealing by laser, resistance, or ultrasonic welding
In laser welding and resistance welding, the material is heated to a molten state. Ultrasonic welding, on the other hand, generates localized frictional heat at the joint zone and is considered a gentle process due to the low total heat input.
Soldering for the secure closure of metal housings
Soldering is a proven method for metal housings, but also for joining glass and metal. This creates solid connections that are almost completely impermeable to gases and liquids.
Bonding with special resins or adhesives
Adhesives and resins can seal; however, true hermeticity generally requires glass/ceramic-to-metal seals or specifically validated epoxy hermetic designs. In the field of electronics, LED modules in particular are protected from damage caused by external influences with resin seals. Special adhesives effectively seal electronic components made of plastic, metal, ceramic, and glass against material exchange.
Glass-to-metal or ceramic-to-metal feedthroughs
In the packaging of electronic components, sealing with glass-to-metal connections plays an essential role. By means of soldering or welding, it is possible to produce solid connections made of ceramic and metal for hermetic sealing.
Airtight packaging for cosmetics
Many consumers choose to use cosmetics without preservatives. To ensure that the products maintain impeccable qualityuntil the packaging is opened for the first time, hermetic sealing is recommended.
Vacuum packaging, jars, and tin cans
Perishable goods such as meat and cold cuts stay fresh longer in airtight vacuum packaging. If jars and cans are hermetically sealed, neither air nor moisture or bacteria can penetrate. This ensures a long shelf life for pickled fruits and vegetables, fruit purée, jam, and vegetables.
Hermetic seals in electronics
In electronics, the process of hermetic sealing has proven its worth in the packaging of sensitive functional parts such as memories and chips. Electronic components such as sensors, batteries, and connectors are also perfectly protected from damaging environmental influences in hermetically sealed housings.
Application of the process in industry and mechanical engineering
Components of plants in industry and mechanical engineering are secured with a hermetic seal against the escape of liquids such as gases and oil due to leaks. Hermetic housings are suitable for sealing pumps, individual valves, and gears of machines.
Hermetic sealing for technical plants and components
Hermetic sealing for technical plants and components ensures gas-tight encapsulation. It is typically achieved through cohesive joining processes such as welding or soldering, as well as through glass/ceramic-to-metal seals and hermetic feedthroughs. Elastomer seals (e.g., O-rings) are only suitable to a limited extent, as they are open to diffusion. The required degree of tightness is defined application-specifically via leak rates (e.g., He leak), validated, and monitored during operation depending on the risk.
Not to be confused with IP protection ratings (dust/water): Hermeticity refers to gas-tightness and is verified separately via leak rates.
Hermetic sealing in medicine and pharmacy
Sterile-packaged medications, medical devices, and implants, such as pacemakers and artificial joints, are protected from contamination in hermetically sealed packaging. They can be stored until the expiration date in such a way that there is no risk of infection when they are used. The Blow-Fill-Seal process has established itself as a standard in clinics, medical practices, emergency services, and for medical personnel due to the minimization of contamination risks. In their daily work, clinics, medical practices, and emergency services must be able to rely on sterile pharmaceuticals. The BFS system minimizes contamination risks to a negligible level through its fully automated process.
Hermetic sealing in pharmaceutical packaging
Hermetic sealing is particularly important for pharmaceutical products. Here, sterility and the protection of the quality of the preparations are the top priorities. These criteria are indispensable for the protection of the physical integrity of patients. The standards for sealing pharmaceutical packaging are therefore regulated by law.
For sterile drugs, EU-GMP Annex 1 regulates the requirements for Container Closure Integrity (CCI) and the validation of deterministic testing methods (e.g., according to USP <1207>). Inspection is carried out by the responsible national authorities; the European Medicines Agency (EMA) coordinates guidelines and inspection networks. For the US market, 21 CFR 211.94 additionally applies.
Selected methods for sealing pharmaceutical products
In addition to BFS, other sealing processes exist, such as heat sealing, flame or laser sealing, induction sealing, and the bonding of sealants, which find application in other industrial sectors.
Heat Sealing
Packaging made of a combination of plastic and aluminum is effectively protected against contamination by the heat sealing process. In heat sealing, the edges of the package made of thermoplastic films are fused together using heat and pressure.
Flame, Crimp, and Laser Sealing (Ampoules & Vials)
Glass ampoules are hermetically closed directly after filling by flame sealing (tip/pull seal); the glass-to-glass melt forms the gas-tight seal.
Glass vials, on the other hand, are closed with an elastomer stopper and crimped with an aluminum cap; the tightness arises from the coordinated system of vial neck, stopper, and crimp and must be validated by means of CCI tests. A flip-off or protective cap primarily serves as a tamper-evident seal and reduces contamination risks on the outside, but is not part of the hermetic seal. Laser sealing can offer advantages for suitable plastic or composite systems (clean, locally limited), but requires laser-transparent materials and a matching design.
The tightness of vials must be verified during the process via CCI testing (e.g., according to USP <1207>); for glass ampoules, flame sealing remains the standard.
Induction Sealing
Induction sealing is suitable for closing bottles with liquid medications, such as cough syrup. If the aluminum foil for the closure is heated by means of electromagnetic induction, it is firmly bonded to the neck of the bottle.
Bonding with sealants
In pharmaceutical applications, approved sealants are used selectively (e.g., for component/device connections). For primary packaging, however, bonding is rarely a hermetic closure; CCI requirements are predominantly met by flame/thermal sealing, crimp closures, or validated welding processes.