Why Does Steam Sterilization of Instruments Require Vacuum?
And When Is Steam Sterilization Without Vacuum Used?
In steam sterilization, air is a critical factor that directly determines sterilization effectiveness.
The integration of a vacuum system is not an optional feature, but a fundamental requirement to ensure safety and standardization in infection control practices.
1. Removal of Air from the Sterilization Chamber and Instruments
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- Air acts as a thermal insulator, preventing saturated steam from making direct contact with instrument surfaces.
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- When air remains in the chamber or inside instruments: Heat distribution becomes uneven. Cold spots are likely to occur, leading to areas that do not meet sterilization conditions.
2. Ensuring Deep Penetration of Steam into All Areas
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- Saturated steam is only effective at microbial inactivation when it directly contacts the surface.
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- Vacuum enables steam to penetrate deeply into: Lumens and hollow channels. Tubes, joints, and complex instrument structures
3. Faster Achievement of Sterilization Temperature
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- Once air is removed, saturated steam can rapidly reach standard sterilization temperatures of 121-134°C.
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- This shortens cycle time and improves overall process efficiency.
4. Elimination of Cold Air Pockets
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- Cold air pockets are residual air zones that fail to reach sterilization temperature.
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- Vacuum effectively eliminates this risk, ensuring uniform thermal conditions throughout the chamber.
5. Supporting Post-Sterilization Drying
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- After sterilization, vacuum removes condensed steam, allowing instruments to dry faster.
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- Dry instruments: Reduce the risk of recontamination during storage. Improve safety for subsequent clinical use
In practice, vacuum-assisted steam sterilization consists of two critical stages: Pre-vacuum và Post vacuum:
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- Pre-vacuum (Conducted before steam injection): Essential for complex loads such as: Hollow instruments, Cannulas and needles, Porous materials. Without air removal, steam penetration is severely compromised.
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- Post-vacuum (Performed after sterilization): Ensures instruments are dry, preventing: Corrosion, Mold growth, Safety risks during immediate patient use
Vacuum performance is critically important and must be evaluated carefully against recognized standards (e.g. EN 285), as well as validated sterilization processes prior to equipment procurement.
Special attention should be paid to avoid misleading marketing practices, where some suppliers equate “vacuum drying” with the entire vacuum sterilization process.
Vacuum drying alone cannot replace a true pre-vacuum steam sterilization cycle.
As analyzed above, air is the direct cause of sterilization failure. Therefore, the method of air removal has become the primary criterion distinguishing two types of steam sterilizers:
1. Gravity Displacement Sterilizers - Air removal by density difference
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- Operating principle: Hot steam (lighter) rises upward. -> Cold air (heavier) is pushed downward and expelled through the drain valve.
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- Limitations: Air is not completely removed. Residual air is easily trapped in: Narrow gaps, Hollow instruments, Textile-wrapped loads. Steam penetration is limited, especially for complex loads.
-> Gravity sterilizers are suitable only for simple loads, where steam can directly contact surfaces from the beginning of the cycle.
2. Vacuum Steam Sterilizers - Active and controlled air removal
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- Operating principle: A vacuum pump removes nearly all air from the chamber. Saturated steam is introduced only after air evacuation.
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- Advantages: Complete air removal before steam injection. Deep steam penetration into: Lumens and hollow channels, Wrapped and textile materials. Uniform, controllable temperature and pressure
-> This is the only mechanism that ensures safe sterilization of complex instruments in modern clinical practice.
If your organization would like further consultation on
vacuum-assisted steam sterilization, please contact
Duong Gia via hotline
+84 939 556 666 for detailed technical support.
Content responsibility: Mr. Nam +84 968 077 996