Autoclave Safety Guide: Standard Operation Procedures (SOP) & Maintenance Tips

LS-B35L-I-A Autoclave

High-pressure steam sterilization works by heating water in a sealed chamber to generate steam. By driving out cold air and sealing the exhaust valve, the internal pressure increases, raising the boiling point of water above 100°C. This high-temperature, saturated steam environment coagulates and denatures bacterial proteins, achieving effective sterilization.

However, improper operation can lead to sterilization failure or safety hazards. Below is the Standard Operation Procedure (SOP) for HINOTEK manual and automatic autoclaves.

Part 1: How to Operate an Autoclave Safely

1. Preparation

Before every use, inspect the autoclave for any abnormalities. Ensure the chamber is clean. Add the appropriate amount of water to the main body.

Note: How much water is “Appropriate”? Different models have different requirements:

  • Portable Hand-Wheel Type: Water level must align with the bottom of the inner bucket support.

  • Portable Digital/Automatic: Water must be higher than the heating element and the water level sensor.

  • Vertical Automatic: Water must completely submerge the heating element.

  • Rule of Thumb: Not too much, not too little. If you are unsure, please send your model number to HINOTEK engineers for confirmation.

2. Loading

Wrap the items to be sterilized in a clean white cloth or place them in the sterilization drum.

  • Leave Gaps: Do not overstuff the chamber. Ensure there is space between packs/items to allow steam to circulate freely. If the steam path is blocked, sterilization will fail.

3. Sealing

Place the items into the chamber. If your model has a manual exhaust hose on the lid, insert it into the inner circular groove. Align the bolts with the slots on the lid.

  • Tightening: Tighten the wing nuts evenly in a diagonal pattern (opposing pairs) to ensure a perfect seal. Loose nuts can cause steam leakage.

4. Heating & Cold Air Purging

 

Plug in the power and start heating. This is the most critical step for sterilization success.

The “Cold Air Purging” Process:

  1. Start: When heating begins, flip the Manual Release Valve to the vertical (OPEN) position.

  2. Purge: As the water boils, steam will push the cold air out of the chamber.

  3. Close: Wait until a steady stream of steam escapes (usually delay for about 1 minute after steam appears). Then, flip the valve to the horizontal (CLOSED) position.

  4. Pressurize: The pressure and temperature will now rise to the set levels.

Why is this important? If you do not purge the cold air, the pressure gauge may read high (e.g., 0.15MPa), but the actual temperature will be too low for sterilization due to air pockets acting as insulation.

5. Sterilization & End of Cycle

Once the pressure/temperature reaches the required level, start the timer. After the sterilization time is over, choose the correct method based on your load type:

Scenario A: Solid Items (Instruments, Dressings) -> “Drying”

For items that need to be dry immediately:

  1. Open the release valve to exhaust steam rapidly.

  2. Wait for the pressure gauge to return to Zero.

  3. Wait an additional 2 minutes.

  4. Open the lid and keep the heater running for 10-15 minutes to evaporate moisture (drying phase).

  5. Unplug the power.

Scenario B: Liquids (Media, Solutions) -> “Natural Cooling”

 

⛔ DANGER: DO NOT OPEN VALVE IMMEDIATELY FOR LIQUIDS! If you exhaust steam quickly while sterilizing liquids, the sudden pressure drop will cause the superheated liquid inside the bottles to boil violently (flash boiling). This causes explosions, bottle bursts, and liquid overflow.

Correct Procedure for Liquids:

  1. Unplug the power immediately after the cycle ends. Stop heating.

  2. Let the autoclave cool down naturally.

  3. Wait until the pressure gauge returns to Zero.

  4. Wait an additional 1-2 minutes.

  5. Open the release valve to release any residual steam.

  6. Open the lid.

Part 2: Daily Maintenance & Care

1. Routine Cleaning

  • Chamber: Keep the exterior and the sterilization chamber clean and dry.

  • Sensors: Clean the temperature probe and water level sensor regularly to prevent scale buildup.

  • Gasket Care: Check the silicone door gasket for damage. Tip: Apply a layer of talcum powder to the gasket after daily use to extend its lifespan.

  • Steam Trap: Clean the steam trap (hydrophobic valve) monthly to ensure it drains condensate effectively.

  • Water Quality: Please use Distilled Water or Deionized Water. (Refer to our water quality guide to avoid limescale damage).

2. Inspection Cycle

  • Annual Check: We recommend a comprehensive inspection by a qualified technician every year (checking the cylinder, door, piping, and electrical systems).

  • Calibration: Safety valves, temperature gauges, and pressure gauges should be calibrated annually to ensure accuracy.

3. Storage

If the equipment will not be used for a long time:

  • Store in a ventilated, dry place. Cover it to protect from dust.

  • Drain all water from the main body/generator.

  • Leave the door/lid slightly open to keep the chamber dry and prevent odors.

4. Operational DOs and DON’Ts

  • Training: Only trained personnel should operate the autoclave. Never leave it unattended during the cycle.

  • Water Watch: Do not rely solely on the automatic water protection. Visually check water levels frequently to prevent burning the heating element.

  • Adding Water: Always cut the power and release pressure (open release valve) before adding water. Never open the inlet valve if there is pressure in the jacket.

  • Door Safety: Never force the door open if the interlock handle cannot be lifted or if there is any pressure remaining.

  • Liquid Safety: When sterilizing liquids, only open the door when the liquid temperature has dropped below 70°C.

  • Restarting: If power is lost or temperature drops below the standard during the cycle, you must restart the timer once the temperature recovers.

  • Safety Valve Test: Weekly, pull the handle on the safety valve (while under low pressure) to ensure it releases steam and snaps back correctly.

  • Blowdown: If your unit has a steam generator, drain the water under pressure daily to remove scale and sediment.

  • Duty Cycle: Continuous use should ideally be less than 8 hours per day.

To understand the fundamental principles common to all types of Autoclave,  be sure to read our main article: What is An Autoclave-Principles, Applications, and Procurement.

This guide is maintained by HINOTEK’s core technical team, comprised of senior engineers and application scientists with over two decades of hands-on experience in fields such as microscopy, centrifugation, and autoclave. We are committed to ensuring that every piece of information in this guide—from instrument principles and technical specifications to laboratory procurement advice—maintains the highest level of accuracy and timeliness.

This content is regularly reviewed and updated to reflect the latest industry standards and technological advancements. We value feedback from the global scientific community. Should you have any questions or suggestions, or wish to discuss any technical details, please do not hesitate to contact our expert team at [email protected].

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