Pre-Operation Inspection
Pre-operation inspection is the primary step in ensuring safety. Before each use, the following items must be checked:
- Safety Valve and Exhaust Valve: Check that the safety valve and exhaust valve screws and knobs are intact, that the safety valve is within its calibration period, and that the lead seal is intact.
- Thermometer and Pressure Gauge: Confirm that the thermometer and pressure gauge are intact and within their calibration periods.
- Exhaust Pipe: Ensure the exhaust pipe is clear and unobstructed.
- Water Level: The water level inside the pot must reach the indicator line. Check that no debris is present inside the sterilization pot.
- Water Quality Requirements: Before use, add distilled water or pre-boiled water to the autoclave to minimize scale formation. Scale severely affects heating efficiency and shortens equipment service life.
Loading and Sealing
Loading and sealing also require proper technique. Specific requirements are as follows:
- When placing items to be sterilized into the inner pot, take care to prevent liquid overflow. Do not place bottle stoppers too close to the bucket wall to prevent condensation from wetting the cotton stoppers.
- Avoid over-packing sterilization items; leave channels for steam circulation.
- After covering the container lid, ensure it fits completely flush with the sterilization pot rim for proper sealing.
Heating and Venting
Heating and venting are critical steps for ensuring sterilization effectiveness:
- Begin heating until 102 degrees Celsius, at which point the solenoid valve controlled by the temperature controller automatically releases air, expelling cold air from inside the sterilization pot. This step is absolutely critical.
- If cold air is not fully expelled, the internal pot temperature will not reach the specified temperature, directly affecting sterilization effectiveness.
- Even if the pressure gauge indicates the required pressure value, if mixed with cold air, the actual temperature will be lower than the corresponding temperature under pure steam conditions, leading to sterilization failure.
Pressure Holding and Cooling
The pressure holding and cooling phase requires special safety attention. Key points are:
- When the pressure gauge pointer reaches the required pressure setting, the system begins timing and maintains pressure for the required duration.
- Absolutely prohibit rapid air release through the exhaust valve. Doing so may cause two types of harm: (1) Sudden release of high-temperature, high-pressure steam may injure the operator's hands or face. (2) For test tubes or flasks containing culture media, sudden pressure reduction causes the medium to surge and spray out, resulting not only in sample loss but also potential contamination of cotton stoppers or even burns.
The correct procedure is:
- Turn off the power and allow the internal pressure to drop naturally to zero.
- Then open the exhaust valve to release remaining steam.
- Allow slight cooling before opening the pot lid to remove sterile items.
Special note: Even when the pressure gauge reading drops to near 0 MPa, the pot lid must not be opened immediately. The interior still has high temperature, and sudden entry of cold air may cause glassware to shatter.
Regular Maintenance and Inspection
Regular maintenance and inspection must not be overlooked:
- Record any abnormalities that occur during equipment use promptly.
- Perform periodic inspections every 4 to 6 weeks and maintain proper records.
- Regularly check whether the sterilization cabinet door closes tightly. Replace the sealing gasket if sealing is inadequate.
- The steam pressure gauge should be calibrated once per year.
- For sterilization pots with microcomputer automatic control, although operation is simplified, regular inspection of mechanical safety devices such as safety valves and pressure gauges is still required.
Laboratory Management Recommendations
For laboratory managers, the following measures are recommended:
- Establish a two-person system of "one operator, one supervisor" for autoclave operation.
- Post standard operating procedures in graphic form next to the equipment.
- New personnel must pass a practical assessment before operating the equipment independently.
- When the equipment shows abnormal alarms, immediately shut down and contact professional personnel for repair. Self-disassembly and repair are strictly prohibited.
