Autoclave and Ethylene Oxide Sterilization Methods

Autoclave: Moist Heat Sterilization

Autoclave sterilization utilizes moist heat to effectively destroy spores, fungi, bacteria, and viruses. This process requires temperatures above 120°C. The autoclave chamber features a thick, stainless steel wall and a sealing lid. It includes a pressure gauge to monitor temperature and pressure, and a safety valve that activates when pressure reaches a dangerous level. A key controls the steam vent, enabling cooling. The tank contains water up to a specific level and a grid for placing objects. Heating can be electric or gas-powered.

Sterilization Phases in the Autoclave Process

Conditioning

Objects are placed on the grid, the lid is closed, and the vent key is opened.

Exposure to Vapor

The vent key is closed, and pressure begins to build. Once the desired pressure is reached, it is maintained for 15 to 30 minutes under observation.

Evacuation of Steam

The vent key is opened to release steam.

Drying

Heat from the walls and the evacuation of water vapor dry the packages.

Completion

If the gauge indicates zero steam pressure, the lid can be safely opened. This method is suitable for materials that are not damaged by high temperatures or moisture.

Advantages of Autoclave Sterilization

• Rapid: Steam's high penetrating power allows for quick action.
• Economical: Low operating cost.
• Non-toxic: Does not leave toxic residues.
• Easy to Use: Simple operation and control.

Disadvantages of Autoclave Sterilization

• High Temperatures: Not suitable for thermolabile materials.
• Corrosion: May corrode metals.
• Deterioration: Can dull sharp edges.
• Limitations: Cannot be used to sterilize powders, oils, and fats.

Ethylene Oxide Sterilization

Ethylene oxide (EtO) sterilization is a gas-based method commonly used in hospitals alongside autoclaving. EtO is a clear gas, nine times denser than air at room temperature. Due to its toxicity upon contact and inhalation, as well as its flammable and explosive nature, it is typically mixed with other gases to minimize risks (2015). EtO effectively kills microorganisms quickly and has excellent penetrating power without damaging materials. It is used at temperatures between 30°C and 60°C. Aeration is crucial to remove residual gas toxicity.

Phases of Ethylene Oxide Sterilization

Conditioning

The chamber is preheated, materials are loaded, the chamber is closed, and air is removed.

Humidification and Gas Exposure

Water vapor is introduced, followed by the EtO gas. The required exposure time is maintained.

Evacuation and Aeration

The gas is evacuated, and air is introduced several times to remove residual EtO.